Muscle, Neuromuscular, and Cardiac Damage in Trail Running: A Systematic Review
Systematic review registered in PROSPERO CRD420251135043 · 2026 · Systematic review indexed in PubMed
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Supports: Trail running, especially with steep descents and high eccentric load, produces meaningful acute muscular and neuromuscular stress; downhill exposure and recovery deserve monitoring alongside distance and heart rate
Effect: Fifteen studies and 247 participants showed consistent increases in muscle damage markers and acute drops in neuromuscular performance after trail races; the cardiac stress observed was generally transient.
Limitations: Small samples, heterogeneous designs and under 10% female representation. It does not allow converting meters of descent into individual risk or setting a universal recovery window; the person's actual response still rules.
ITRA Discover Trail Running — Km-effort and endurance points
International Trail Running Association · 2026 · ITRA
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Supports: The public ITRA convention calculates effort-kilometers by adding the distance in kilometers plus one extra kilometer for every 100 meters of positive elevation gain
Effect: The classification assigns 0 points below 25 effort-km, 1 for 25–44, 2 for 45–74, 3 for 75–114, 4 for 115–154, 5 for 155–209 and 6 for 210 or more.
Limitations: It is a classification convention, not a physiological equation or a time prediction. On its own it does not account for technicality, descent, mud, altitude, weather, stops or runner skill; Horme shows those limitations next to the result.
American College of Sports Medicine Position Stand. Resistance Training Prescription for Muscle Function, Hypertrophy, and Physical Performance in Healthy Adults: An Overview of Reviews
Currier BS, D'Souza AC, Singh MAF et al. · 2026 · Medicine and science in sports and exercise
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Supports: Strength prescription should be matched to the outcome: heavy loads and frequent practice favor strength; more volume favors hypertrophy; moderate loads moved with fast intent favor power
Effect: Synthesis of 137 systematic reviews and over 30,000 participants: heavy loads prioritize strength, accumulated volume prioritizes hypertrophy, and maximal intent with moderate loads prioritizes power.
Limitations: Evidence groups different populations, exercises, and durations. It does not convert a combination of sets, load, or frequency into a universal dose for each individual.
The Resistance Training Dose Response: Meta-Regressions Exploring the Effects of Weekly Volume and Frequency on Muscle Hypertrophy and Strength Gains
Pelland JC, Remmert JF, Robinson ZP et al. · 2026 · Sports medicine (Auckland, N.Z.)
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Supports: More weekly volume usually increases strength and hypertrophy, but with diminishing returns; frequency contributes mainly by spreading out practice and volume
Effect: 67 studies and 2,058 participants: positive relationship with diminishing returns for volume; effect compatible with small or trivial for frequency on hypertrophy when controlling for volume, and diminishing positive relationship for strength.
Limitations: Meta-regression across studies, not an individual curve. Does not validate universal MEV/MAV/MRV thresholds; Horme's bands are starting points that require personal recalibration.
The effects of velocity-based vs. percentage-based resistance training on sports performance in trainedindividuals: a systematic review and meta-analysis
Wang Y, Qiu J, Dai D et al. · 2026 · BMC sports science, medicine & rehabilitation
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Supports: Velocity-based training can help control quality and fatigue, but it has not shown a clear advantage in maximal strength over well-executed percentage-based programming
Effect: 17 studies and 348 participants; small advantages in jumping/change of direction, with no significant difference in maximal strength or sprinting.
Limitations: Small samples and heterogeneous protocols/sensors. Velocity is a useful signal, not an obligation or a source to fabricate watts when not measured.
The Resistance Training Dose Response: Meta-Regressions Exploring the Effects of Weekly Volume and Frequency on Muscle Hypertrophy and Strength Gains
Pelland JC, Remmert JF, Robinson ZP et al. · 2026 · Sports medicine (Auckland, N.Z.)
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Supports: Volume predicts hypertrophy and strength better when indirect sets count fractionally; the relationship is continuous and shows diminishing returns, not universal MEV/MAV/MRV cut-offs
Effect: Included 67 studies and 2,058 participants. Compared total, direct, and fractional set counting; fractional counting demonstrated the greatest relative empirical support. Volume showed a positive slope with diminishing returns for hypertrophy and, more pronouncedly, for strength.
Limitations: 79% of subjects were young men, and the model assigned all indirect sets as 0.5; authors note actual weighting varies with exercise biomechanics, target muscle, rep ranges, and training history. Horme uses broad categories and states inherent uncertainty, avoiding spurious decimal precision.
The development and implementation of the Australian Physical Activity and Exercise Intensity Terminology
Bishop DJ, et al. · 2025 · Journal of Science and Medicine in Sport
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Supports: Aerobic intensity should be communicated with standardized terms and perceptual cues in addition to physiological zones; a five-level scale makes it easier to use the same language across people and modalities
Effect: The consensus proposes five categories — very low, low, moderate, high and very high — with perceived-exertion descriptors, applicable across ages, sexes, genders, abilities and modalities.
Limitations: It's a consensus terminology proposal, not a clinical outcomes trial. Heart-rate zones and RPE still carry individual error, so Horme shows both and prioritizes measured thresholds when available.
Does Muscle Length Influence Regional Hypertrophy? A Systematic Review and Meta-Analysis
Varovic D, Wolf M, Schoenfeld BJ et al. · 2025 · International journal of sports medicine
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Supports: Training at long muscle lengths may slightly change regional hypertrophy, but the average effects are trivial or small and do not justify declaring all lengthened partials superior
Effect: 12 studies in young adults; regional effects generally trivial, with a favorable trend in some distal regions when training at long muscle lengths.
Limitations: Few muscles, young participants, and short protocols. Does not estimate the fatigue cost of adding partials after failure.
Increasing set volume relative to baseline does not augment skeletal muscle adaptations when compared to maintenance of baseline training volume in recreationally trained individuals
Moreno EN, Sampson DT, Figueroa EC et al. · 2025 · European journal of applied physiology
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Supports: In already-trained people, automatically increasing volume beyond what is already working does not guarantee more hypertrophy or strength; maintaining an effective dose can be just as productive
Effect: In 42 trained adults, 12 weeks of increased volume for elbow flexors failed to yield greater gains in muscle thickness or 1RM compared to maintaining baseline volume; both conditions improved over non-training controls.
Limitations: The study examined isolated unilateral elbow flexion rather than full-body routines. It does not prove volume increases never help; it cautions against adding volume merely to hit a generic landmark when existing volume is already driving progress.
2024 Adult Compendium of Physical Activities: A third update of the energy costs of human activities
Herrmann SD, Willis EA, Ainsworth BE, et al. · 2024 · Journal of Sport and Health Science
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Supports: Activity METs should be based on the 2024 Adult Compendium, which updated energy cost with a systematic review and replaced estimates with measurements where possible
Effect: Reviewed 32,173 abstracts and 1,507 full texts, extracted 2,356 energy expenditure values from 701 articles, and published 1,114 activities; 912 have measured MET values and 202 estimated.
Limitations: A standard MET remains a population average and not an individual calorimetry. Efficiency, age, body composition, technique, equipment, and environment can alter actual expenditure; that is why Horme displays a range and the method, not exact calories.
High‐intensity interval training and cardiorespiratory fitness in adults: An umbrella review of systematic reviews and meta‐analyses
Poon ETC, Li HY, Gibala MJ, Wong SHS, Ho RST · 2024 · Scandinavian Journal of Medicine & Science in Sports
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Supports: HIIT improves cardiorespiratory fitness in adults and, on average, achieves a small to moderate advantage over moderate-intensity continuous training
Effect: Gathered 24 systematic reviews with meta-analyses, 429 primary studies, and 12,967 participants. Compared to continuous training, reviews reported improvements of 0.52 to 3.76 ml/kg/min in cardiorespiratory fitness, depending on population and protocol.
Limitations: The AMSTAR-2 quality of many reviews was moderate to critically low, and HIIT protocols were highly heterogeneous. It does not support doing all volume at high intensity or using the same protocol for everyone.
Physical Activity in the Prevention of Weight Gain and Obesity in Adults: An Updated Position Stand
Jakicic JM, et al. · 2024 · Medicine & Science in Sports & Exercise
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Supports: The evidence doesn't support a single physical activity modality as superior for losing weight or adiposity; a sustainable combination of aerobic activity, strength and less sedentary time allows better individualization
Effect: The consensus review concludes that effects depend on dose and adherence and that there's insufficient evidence to declare one activity mode universally superior for controlling weight or adiposity.
Limitations: Body composition change also depends on intake, sleep, medication and clinical context. Composition alone doesn't predict tolerance, performance or the modality a person will stick with.
Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions
Robinson ZP, Pelland JC, Remmert JF et al. · 2024 · Sports medicine (Auckland, N.Z.)
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Supports: Always going to failure is not necessary to gain strength; in hypertrophy, getting close to failure may matter, but the exact relationship and the optimal dose remain uncertain
Effect: Strength gains were similar across a wide range of RIR; hypertrophy showed a favorable trend when training closer to failure.
Limitations: RIR was estimated and the hypertrophic relationship is considered exploratory. It does not prove that momentary failure is superior or that it must necessarily be reserved for the final set.
Give it a rest: a systematic review with Bayesian meta-analysis on the effect of inter-set rest interval duration on muscle hypertrophy
Singer A, Wolf M, Generoso L et al. · 2024 · Frontiers in sports and active living
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Supports: Resting longer than 60 seconds may preserve volume better and give a small hypertrophy advantage; beyond about 90 seconds the average differences are small
Effect: Small average advantage for rest intervals over 60 s, likely mediated by preserving repetitions and volume; minimal noticeable differences above 90 s.
Limitations: Few studies and heterogeneous protocols. In heavy strength or power, more rest may be needed to preserve performance even if average hypertrophy changes little.
Muscle hypertrophy response across four muscles involved in the bench press exercise: Randomized 10 weeks training intervention
Lanza MB, Prado GC, Lacerda LT et al. · 2024 · Journal of bodywork and movement therapies
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Supports: The bench press produces hypertrophy in several of the muscles involved, but not to the same degree; one set should not be credited equally to the pectorals and the triceps
Effect: Following 10 weeks of bench pressing, involved muscles grew, but pectoralis major hypertrophied more than triceps brachii and pectoralis minor; medial deltoid displayed lesser adaptation.
Limitations: A single study of one exercise, sample, and program does not establish a universal muscle-weighting coefficient. Horme uses it to categorize prime movers, co-agonists, and synergists, not to convert hypertrophy ratios into rigid percentages.
Maximal Number of Repetitions at Percentages of the One Repetition Maximum: A Meta-Regression and Moderator Analysis of Sex, Age, Training Status, and Exercise
Nuzzo JL, Pinto MD, Nosaka K, Steele J · 2024 · Sports Medicine
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Supports: The number of reps you can do at each percentage of 1RM barely changes with sex, age or training status; it does change with the exercise
Effect: 952 reps-to-failure tests in 7,289 people (269 studies). Sex, age and training status had little influence; more reps are done in the leg press than in the bench press at the same relative intensity.
Limitations: Two thirds of the groups were men and 92% were under 59; bench press and leg press dominate the data. Variation BETWEEN people is large, which is why Horme adjusts with RIR and not only with percentages.
Non-occupational physical activity and risk of cardiovascular disease, cancer and mortality outcomes: a dose–response meta-analysis of large prospective studies
Garcia L, Pearce M, Abbas A, et al. · 2023 · British Journal of Sports Medicine
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Supports: The relationship between aerobic activity and health is gradual: the largest marginal benefits appear when going from nothing to something, and much of the benefit accumulates near 8.75 mMET-h/week, with diminishing returns above that
Effect: Included 196 articles, 94 cohorts, and over 30 million participants. At 8.75 mMET-h/week, the association was RR 0.69 for all-cause mortality and RR 0.71 for cardiovascular mortality; the curve showed particularly large benefits starting from the lowest activity levels.
Limitations: This is observational evidence and does not prove individual causality. The minute equivalence depends on intensity and does not turn 150 minutes into an exact biological threshold; Horme uses it as a dose-response reference, not a universal examination.
Current evidence shows no influence of women's menstrual cycle phase on acute strength performance or adaptations to resistance exercise training
Colenso-Semple LM, D'Souza AC, Elliott-Sale KJ, Phillips SM · 2023 · Frontiers in Sports and Active Living
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Supports: Current evidence does not justify automatically changing volume, load or proximity to failure based on an estimated menstrual phase; individual symptoms and performance are more useful signals
Effect: Findings across reviews were highly variable and methods to confirm cycle phase were poor or inconsistent. The authors consider it premature to conclude that hormonal fluctuations appreciably change acute performance or chronic strength and hypertrophy adaptations.
Limitations: The absence of a clear population effect doesn't mean a person has no relevant symptoms. That's why Horme lets you autoregulate by readiness, pain and performance, but doesn't prescribe by calendar.
Greater Gastrocnemius Muscle Hypertrophy After Partial Range of Motion Training Performed at Long Muscle Lengths
Kassiano W, Costa B, Nunes JP, Ribeiro AS, Schoenfeld BJ, Cyrino ES · 2023 · Journal of Strength and Conditioning Research
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Supports: This trial found greater gastrocnemius hypertrophy with long-length partials in its protocol. It does not show that full range is always superior or that all partials are better.
Effect: In this trial, training the calf in the STRETCHED portion of the range produced more hypertrophy than the full range or the shortened portion, reinforcing that the stretched position (long muscle length) is especially stimulating. The wider line of evidence (Pedrosa 2022, Wolf/Schoenfeld 2023) points the same way for other muscles, though the effect size is moderate and exercise-dependent.
Limitations: It's a calf study lasting ~2 months with ultrasound measurement; generalizing to other muscles rests on additional studies, not this one alone. The "optimal" ROM depends on the joint and the technique. Horme uses it as a soft selection bias (flagging certain accessories as higher stretch-stimulus), never as a rigid rule.
Influence of Resistance Training Proximity-to-Failure on Skeletal Muscle Hypertrophy: A Systematic Review with Meta-analysis
Refalo MC, Helms ER, Trexler ET, Hamilton DL, Fyfe JJ · 2023 · Sports Medicine
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Supports: For hypertrophy, training close to failure matters more than reaching absolute failure: leaving 0-3 reps in reserve produces similar muscle growth, and taking every set to complete failure adds fatigue with no clear advantage
Effect: Hypertrophy was similar whether training to failure or leaving reps in reserve; the proximity-to-failure/hypertrophy relationship was weak. For pure strength, training a bit further from failure tended to be slightly better. The practical takeaway: accumulating effective sets close to failure (RIR 0-3) is enough, with no need to fail on every one.
Limitations: The studies are heterogeneous in how they define and verify 'failure'; few very advanced participants. It supports the RIR autoregulation Horme already uses (rir-autoregulation): the target is proximity to failure, not mandatory failure.
Exercise training and resting blood pressure: a large-scale pairwise and network meta-analysis of randomised controlled trials
Edwards JJ, Deenmamode AHP, Griffiths M, et al. · 2023 · British Journal of Sports Medicine
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Supports: Isometric training is the exercise type that lowers resting blood pressure most; the isometric wall squat stood out among variants
Effect: 270 trials and 15,827 participants. Isometrics −8.24/−4.00 mmHg vs −4.55/−3.04 for dynamic resistance training and −4.49/−2.53 for aerobic training. The isometric wall squat was the most effective submode for systolic pressure.
Limitations: Isometric trials are smaller and shorter than aerobic ones, and network rankings carry uncertainty. It complements, not replaces, other physical activity or prescribed medication.
Effect of free-weight vs. machine-based strength training on maximal strength, hypertrophy and jump performance – a systematic review and meta-analysis
Haugen ME, Vårvik FT, Larsen S, et al. · 2023 · BMC Sports Science, Medicine and Rehabilitation
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Supports: Free weights and machines produce similar strength and hypertrophy gains; strength improves more in the format you train with
Effect: 13 studies and 1,016 participants. No differences in direct comparisons of dynamic strength (SMD 0.08), isometric strength, jumping or hypertrophy (SMD −0.06); strength measured with free weights improved more with free weights (SMD −0.21).
Limitations: Few hypertrophy studies and adults aged 18–60, mostly men. The choice depends on preferences and goals.
Individualized Exercise Prescription and Improvements in Cardiorespiratory Fitness in Adults
Martini AD, et al. · 2022 · International Journal of Environmental Research and Public Health
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Supports: Setting aerobic intensity to individual physiological thresholds may increase the likelihood of improving cardiorespiratory fitness compared with using only population percentages of heart rate reserve
Effect: In 49 inactive adults over 12 weeks, 79% of the group with individualized prescription by ventilatory thresholds responded versus 47% of the group standardized by heart rate reserve (p=0.04).
Limitations: Small sample, initially inactive adults and laboratory-measured thresholds. It doesn't show that an automatic formula is personalized; Horme uses history and its own tests when available and keeps conservative margins.
Compatibility of Concurrent Aerobic and Strength Training for Skeletal Muscle Size and Function: An Updated Systematic Review and Meta-Analysis
Schumann M, Feuerbacher JF, Sünkeler M, et al. · 2022 · Sports Medicine
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Supports: Combining cardio and strength does not meaningfully reduce hypertrophy or maximal strength on average; the main interference signal appears in explosive strength when both are done within the same session
Effect: In 43 studies, no significant impairment on hypertrophy (SMD -0.01) or maximal strength (SMD -0.06) was observed. Explosive strength did show a small attenuation (SMD -0.28), clearer when cardio and strength shared the same session.
Limitations: Studies were heterogeneous and do not allow prescribing an exact hourly separation for each individual. The app prioritizes the primary session and uses individual response, rather than assuming that all cardio causes interference.
Muscle-strengthening activities are associated with lower risk and mortality in major non-communicable diseases: a systematic review and meta-analysis of cohort studies
Momma H, Kawakami R, Honda T, Sawada SS · 2022 · British Journal of Sports Medicine
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Supports: Doing ~30-60 minutes of strength training per week is associated with lower all-cause mortality and lower risk of cardiovascular disease, cancer and diabetes, independently of aerobic exercise
Effect: Muscle-strengthening activities were associated with 10-17% lower all-cause, CVD and cancer mortality; the association with total mortality traced a J-shaped curve bottoming out around 30-60 min/week (more volume added no further longevity benefit).
Limitations: Observational studies (association, not causation); activity was measured by self-report. It doesn't change training prescription, but it puts in context that the effective minimum for health is modest.
Daily steps and all-cause mortality: a meta-analysis of 15 international cohorts
Paluch AE, Bajpai S, Bassett DR, Carnethon MR, Ekelund U, Evenson KR, et al. · 2022 · The Lancet Public Health
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Supports: Mortality falls continuously with daily steps until it flattens out around 6,000–8,000 steps in people over 60 and 8,000–10,000 in those under 60
Effect: Individual participant data meta-analysis of fifteen cohorts with accelerometry (over 47,000 adults). Comparing the highest with lowest quartile of daily steps, all-cause mortality reduction was approximately 40–53%. The curve is monotonic but PLATEAUS: above the plateau, further steps yield diminishing returns. Stepping cadence/intensity contributed little after adjusting for total step volume.
Limitations: Cohort studies: association, not causality, and reverse causality (illness causes less walking) remains a plausible factor despite adjustment. The ubiquitous '10,000 steps' goal originated not from scientific trials, but from a 1965 Japanese commercial marketing campaign. Horme targets the plateau threshold and explicitly notes that walking MORE matters more than walking faster.
Association of wearable device-measured vigorous intermittent lifestyle physical activity (VILPA) with mortality
Stamatakis E, Ahmadi MN, Gill JMR, Thøgersen-Ntoumani C, Gibala MJ, Doherty A, Hamer M · 2022 · Nature Medicine
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Supports: Short bouts (1–2 min) of incidental vigorous activity spread through the day are associated with lower mortality even in adults who do no structured exercise at all
Effect: In a large cohort with wrist accelerometry, three daily bouts of approximately 1–2 minutes of incidental vigorous physical activity (brisk stair climbing, uphill walking, carrying heavy loads) were associated with substantial reductions in all-cause, cardiovascular, and cancer mortality in non-exercisers.
Limitations: Observational: association, not causality, carrying risk of reverse confounding despite sensitivity checks. Measurement stems from wrist accelerometry, which infers intensity indirectly. Horme offers this ONLY to individuals below physical activity baselines: for structured trainees it adds little and creates distraction.
The Effect of Load and Volume Autoregulation on Muscular Strength and Hypertrophy: A Systematic Review and Meta-Analysis
Hickmott LM, Chilibeck PD, Shaw KA, Butcher SJ · 2022 · Sports Medicine - Open
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Supports: Autoregulating load with RIR or velocity produces strength gains similar to fixed percentages; ending sets with less velocity loss favors strength and with more loss favors hypertrophy
Effect: 15 studies. Autoregulated vs standard: +2.07 kg 1RM (CI −0.32 to 4.46; not significant). Velocity loss ≤25%: +2.32 kg 1RM but less hypertrophy than >25%.
Limitations: Few studies per comparison and trained people. The practical advantage is adjusting to the day, not a demonstrated larger effect.
Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression
Murphy C, Koehler K · 2022 · Scandinavian Journal of Medicine & Science in Sports
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Supports: Strength training in a calorie deficit keeps strength gains but reduces lean mass gains; a deficit of about 500 kcal/day can prevent them
Effect: Lean mass worse in a deficit than without one (ES −0.57); strength comparable (ES −0.31, not significant). The meta-regression places at ~500 kcal/day the deficit that cancels lean mass gain.
Limitations: Trials of at least 3 weeks with varied populations; the 500 kcal threshold is an average estimate, not an individual limit.
Physiological Indicators of Trail Running Performance: A Systematic Review
de Waal SJ, Gomez-Ezeiza J, Venter RE, Lamberts RP · 2021 · International Journal of Sports Physiology and Performance
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Supports: Trail performance is multifactorial: aerobic capacity, threshold, maximal aerobic speed, economy, body composition, age and the specific race profile each explain different parts, and they cannot be reduced to a single flat-ground pace
Effect: Seven studies met the criteria. The most frequent associations involved maximal aerobic capacity, lactate threshold, maximal aerobic speed and economy; multivariable models explained between 48% and 99% of the variance in specific samples and courses.
Limitations: Only seven studies were included and there was substantial heterogeneity in distances, profiles and levels. The predictors are not interchangeable across courses and cannot promise an individual time; Horme uses them for context, not to issue a universal score.
Methodological Considerations for Studies in Sport and Exercise Science With Women as Participants: A Working Guide for Standards of Practice for Research on Women
Elliott-Sale KJ, Minahan CL, de Jonge XAKJ, et al. · 2021 · Sports Medicine
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Supports: Cycle length, the actual timing of ovulation and the individual response to each phase vary widely between women and from cycle to cycle in the same woman — a calendar method (date + average length) is an estimate, not a direct hormonal measurement
Effect: This isn't a quantitative finding: it's a methodological guideline recommending that cycle phase be confirmed with objective methods (LH, basal temperature) whenever possible, precisely because the calendar method (counting days since the last period started) carries a real margin of error against the exact hormonal timing — the method Horme uses, being the only one possible without lab tests.
Limitations: It's a good-practice guideline for research, not a study with an effect size of its own; it's cited here to be honest about the real limits of the calendar method the app uses — which is why Horme's adjustments are deliberately gentle and always switchable off.
ACSM's Guidelines for Exercise Testing and Prescription (11th edition)
American College of Sports Medicine (Liguori G, ed.) · 2021 · Wolters Kluwer (reference manual)
Supports: Submaximal and maximal field tests (1.5 miles, walking mile, step test) are validated alternatives to the laboratory exercise test for estimating cardiorespiratory fitness
Effect: The manual compiles protocols and prediction equations for widely used field tests—including the 1.5-mile run, the Rockport 1-mile walk test (Kline et al., 1987), and step tests—along with typical estimation errors ranging from ~3.5 to ~5.5 ml/kg/min depending on protocol.
Limitations: These are ESTIMATES: each equation's error is several times larger than the difference a user aims to detect across sessions, so they only make sense compared against oneself using the SAME protocol. Submaximal tests add the error of assuming a linear heart-rate-to-VO2 relationship. Horme always shows the error band and recommends repeating the same test, rather than alternating protocols.
No Time to Lift? Designing Time-Efficient Training Programs for Strength and Hypertrophy: A Narrative Review
Iversen VM, Norum M, Schoenfeld BJ, Fimland MS · 2021 · Sports Medicine
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Supports: With little time, multi-joint exercises with at least 4 weekly sets per muscle close to failure are enough; supersets, drop sets and rest-pause roughly halve time while keeping volume
Effect: Recommends at least one leg push, one pull and one upper-body push, ≥4 weekly sets per muscle at 6–15 RM, a specific warm-up and advanced techniques to save time.
Limitations: Narrative, not systematic, review. Time-saving techniques probably favor hypertrophy more than maximal strength, and longitudinal studies are lacking.
Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum
Schoenfeld BJ, Grgic J, Van Every DW, Plotkin DL · 2021 · Sports
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Supports: Muscular adaptations can be obtained across a wide range of loads: maximal strength is optimized with heavy loads, local endurance with light loads and hypertrophy with almost any load if effort is sufficient
Effect: Proposes replacing the classic repetition continuum with a paradigm in which hypertrophy is achieved across a wide range of loads.
Limitations: Authors' review, not a meta-analysis. The specific figures for each range are for guidance.
Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis
Lopez P, Radaelli R, Taaffe DR, et al. · 2021 · Medicine & Science in Sports & Exercise
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Supports: When sets are taken to failure, hypertrophy is similar with light, moderate or heavy loads, but strength improves more with moderate and heavy loads
Effect: 28 studies and 747 adults. No differences in hypertrophy between loads. Superior strength with heavy (SMD 0.60–0.63) and moderate (0.34–0.35) versus light loads.
Limitations: Includes only sets to failure; with sets far from failure, light loads may fall short. Small samples per study.
Practical models of gain rate (coaching synthesis): tables by Lyle McDonald and Alan Aragon
McDonald L; Aragon AA · 2020 · Practical coaching literature (not a peer-reviewed primary study)
Supports: The realistic maximum rate of muscle gain DEPENDS on training age: a beginner can gain a percentage of body weight per month several times higher than an advanced lifter, who is nearing their ceiling
Effect: As a widely used order of magnitude: year 1 ≈ 1.0–1.5 % of body weight/month, year 2 ≈ 0.5–1.0 %, years 3–4 ≈ 0.25–0.5 %, advanced ≈ 0.1–0.25 %; women, in ABSOLUTE terms (kg), roughly half of that given their lower mass and testosterone. Horme uses these bands as a BALLPARK RANGE, modulated by age, calorie adequacy and adherence — not as a prediction calibrated to the individual.
Limitations: It doesn't come from a single controlled trial or a meta-analysis: it's a synthesis of coaching experience and indirect data (hypertrophy studies measure lean mass changes over weeks/months, not 'maximum muscle per year'). Individual variability (genetics, training response, sleep, stress) is enormous; treat it as a typical scenario, not a personal limit. That's why the app labels it explicitly as a 'population band', distinct from the confidence intervals that are fitted to your own data.
World Health Organization 2020 guidelines on physical activity and sedentary behaviour
Bull FC, Al-Ansari SS, Biddle S, Borodulin K, Buman MP, Cardon G, et al. · 2020 · British Journal of Sports Medicine
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Supports: WHO guidelines call for 150–300 min/week of moderate aerobic activity (or 75–150 of vigorous, or an equivalent combination) PLUS at least 2 days per week of muscle strengthening; the biggest jump in benefit is going from inactivity to some activity
Effect: The dose-response relationship with all-cause mortality is curvilinear: the greatest relative risk reduction occurs in the initial weekly minutes from a sedentary baseline and plateaus above ~300 min/week of moderate activity. The equivalence 1 vigorous min ≡ 2 moderate min is what the guidelines themselves use.
Limitations: Consensus guideline based on reviews of mostly observational studies: associations with mortality do not establish causality, and self-reported activity tends to be overestimated. Thresholds (150/300 min, 2 strength days) are pragmatic cutoffs for public health, not individual optimal doses.
Sex Differences in Resistance Training: A Systematic Review and Meta-Analysis
Roberts BM, Nuckols G, Krieger JW · 2020 · Journal of Strength and Conditioning Research
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Supports: With the same strength program, men and women gain muscle and lower-body strength in similar proportion; women gain more relative upper-body strength
Effect: Hypertrophy: no difference between sexes (ES 0.07; 10 studies). Lower-body strength: no difference (ES −0.21; 23 studies). Relative upper-body strength: moderate effect favoring women (ES −0.60; 17 studies).
Limitations: Young and middle-aged adults, short studies and high heterogeneity for strength. It compares RELATIVE changes: in absolute terms men usually start with more muscle and strength. It doesn't study pregnancy or menopause, which Horme treats as separate stages.
Physical Activity and Exercise During Pregnancy and the Postpartum Period: ACOG Committee Opinion, Number 804
ACOG (American College of Obstetricians and Gynecologists) · 2020 · Obstetrics & Gynecology
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Supports: Without obstetric or medical complications, physical activity during pregnancy and postpartum is safe and desirable, with adaptations and attention to warning signs
Effect: Women who were active before pregnancy can continue; exercise is associated with less gestational diabetes, cesarean and instrumental delivery, and better postpartum recovery.
Limitations: Committee opinion based mostly on observational studies. Contraindications and when to resume loading after birth are assessed by the clinician managing the pregnancy.
Acute Effects of Cluster and Rest Redistribution Set Structures on Mechanical, Metabolic, and Perceptual Fatigue During and After Resistance Training: A Systematic Review and Meta-analysis
Jukic I, Ramos AG, Helms ER, McGuigan MR, Tufano JJ · 2020 · Sports Medicine
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Supports: Cluster sets and rest redistribution maintain more velocity and power per rep and produce less perceived fatigue than traditional sets
Effect: 32 studies. Higher mean (SMD 0.60) and peak velocity (0.41), and higher mean (0.33) and peak power (0.38) during the session, with a smaller drop in velocity and power.
Limitations: These are ACUTE, within-session effects. Whether they translate into more long-term strength is less clear, so Horme offers it as a conditional option.
Tapering and Peaking Maximal Strength for Powerlifting Performance: A Review
Travis SK, Mujika I, Gentles JA, Stone MH, Bazyler CD · 2020 · Sports
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Supports: Peaking protocols for maximal strength rely on reducing volume before competing, but specific evidence in powerlifting is scarce
Effect: Reviews tapering and training cessation before powerlifting competition and concludes that protocols derived from strength athletes are lacking.
Limitations: Most tapering evidence comes from endurance sports; in strength sports it's still adjusted by trial and error.
Effect of Fartlek Training on Maximum Oxygen Consumption in Young Adults
Shingala M, Shukla Y · 2019 · Indian Journal of Physiotherapy and Occupational Therapy
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Supports: Fartlek is a viable way to organize pace changes within an aerobic session, but direct evidence doesn't allow claiming it's superior to other well-dosed intervals
Effect: The trial reported an improvement in maximal oxygen uptake in young adults after Fartlek training; it's used to support the format's feasibility, not its superiority.
Limitations: Small study, young population, a publication with limited methodological information and no basis for claiming superiority over every protocol. Horme presents Fartlek as a flexible interval method, not an exclusive adaptation.
How many times per week should a muscle be trained to maximize muscle hypertrophy? A systematic review and meta-analysis of studies examining the effects of resistance training frequency
Schoenfeld BJ, Grgic J, Krieger J · 2019 · Journal of Sports Sciences
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Supports: Training each muscle ≥2 times/week, at equal total volume, is equal to or better than once a week
Effect: A small but consistent advantage of ≥2×/week over 1×/week per muscle, when total weekly volume is held equal between conditions.
Limitations: Many studies do not equate total volume well between the conditions compared; full-body workouts and splits are mixed together in the analysis; participants are mostly young recreationally trained men.
Wake up and smell the coffee: caffeine supplementation and exercise performance — an umbrella review of 21 published meta-analyses
Grgic J, Grgic I, Pickering C, et al. · 2019 · British Journal of Sports Medicine
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Supports: Caffeine improves strength, power and endurance performance
Effect: A small-to-moderate effect on muscular strength/power and also on aerobic endurance, consistent across the 21 meta-analyses reviewed.
Limitations: Response varies with genetics (caffeine metabolism) and tolerance from habitual intake; most studies use a single laboratory dose, not real daily consumption patterns.
Training and Racing with a Power Meter (3rd edition)
Allen H, Coggan A, McGregor S · 2019 · VeloPress (training manual)
Supports: Functional threshold power (FTP) on the bike can be estimated as 95 % of the average power sustained for 20 minutes all-out
Effect: The 95% factor applied to a 20-minute all-out effort is the benchmark convention in power-meter training, underpinning power zones and derivative metrics (normalized power, intensity factor, and session training load).
Limitations: The 95% is a population approximation: the true relationship between a 20-minute best effort and one-hour sustainable power varies according to individual anaerobic work capacity, which high-anaerobic athletes can overestimate. Requires an actual power meter—GPS-estimated power is unsuitable for this test, and Horme makes this clear. Derived metrics reside exclusively within cardio and do NOT feed the global load model, which operates on a different scale.
Resistance Training for Older Adults: Position Statement From the National Strength and Conditioning Association
Fragala MS, Cadore EL, Dorgo S, Izquierdo M, Kraemer WJ, Peterson MD, Ryan ED · 2019 · Journal of Strength and Conditioning Research
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Supports: Strength training is a powerful intervention against age-related loss of strength, muscle mass and function, and includes power work as well as strength
Effect: Position statement reviewing program design, physiological adaptations, functional benefits and considerations in frailty and sarcopenia; it recommends progressive, individualized programs that include power.
Limitations: A consensus document based on a literature review, not a new meta-analysis. Specific doses must be adapted to comorbidities, frailty and medication.
Blood Flow Restriction Exercise: Considerations of Methodology, Application, and Safety
Patterson SD, Hughes L, Warmington S, et al. · 2019 · Frontiers in Physiology
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Supports: Blood flow restriction training requires a specific methodology (individualized pressure, an appropriate cuff) and safety screening
Effect: Position stand by researchers in the field on applying BFR with resistance exercise, with aerobic exercise and passively to limit atrophy.
Limitations: Expert consensus. Pressure must be individualized to arterial occlusion pressure; improvising with bands or straps doesn't reproduce what was studied.
Isometric training and long-term adaptations: Effects of muscle length, intensity, and intent: A systematic review
Oranchuk DJ, Storey AG, Nelson AR, Cronin JB · 2019 · Scandinavian Journal of Medicine & Science in Sports
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Supports: Isometrics at long muscle lengths produce more hypertrophy than at short lengths, and explosive intent improves rapid force production
Effect: 26 studies. Hypertrophy of 0.86–1.69%/week at long lengths vs 0.08–0.83%/week at short lengths; ballistic intent increased rapid force more; tendons need contractions of ≥70%.
Limitations: Few studies met the inclusion criteria and there's no meta-analysis. An isometric pause within a dynamic rep is a practical application of these findings, not the exact protocol studied.
Including the Nordic hamstring exercise in injury prevention programmes halves the rate of hamstring injuries: a systematic review and meta-analysis of 8459 athletes
van Dyk N, Behan FP, Whiteley R · 2019 · British Journal of Sports Medicine
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Supports: Including the Nordic hamstring curl in prevention programs roughly halves hamstring injuries in athletes
Effect: 15 studies, 8,459 athletes. Risk ratio 0.49 (95% CI 0.32–0.74); 0.52 with randomized trials only and 0.55 without high risk-of-bias studies.
Limitations: Athletes from sprint-based sports; the benefit in non-athletes hasn't been measured. Adherence to the protocol determines the effect.
The Biomechanics and Applications of Strongman Exercises: a Systematic Review
Hindle BR, Lorimer A, Winwood P, Keogh JWL · 2019 · Sports Medicine - Open
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Supports: Strongman exercises have their own biomechanical determinants and likely applications in strength programs, although data for several events are lacking
Effect: 11 articles. In the farmer's walk and heavy sled pull, better athletes have longer strides, higher stride rates and shorter ground contact; quantitative data on the yoke, stones and tire are lacking.
Limitations: Biomechanical evidence, not training trials: it describes how they're done well, not how much they improve other capacities.
Kettlebell training in clinical practice: a scoping review
Meigh NJ, Keogh JWL, Schram B, Hing WA · 2019 · BMC Sports Science, Medicine and Rehabilitation
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Supports: Evidence on kettlebell training is broad but of low quality, with trivial to small effects
Effect: 99 publications included; effect sizes were typically trivial or small and only two trials studied clinical conditions.
Limitations: A scoping review: it describes what exists, it doesn't assess efficacy with a meta-analysis.
Effects of Rest Interval Duration in Resistance Training on Measures of Muscular Strength: A Systematic Review
Grgic J, Schoenfeld BJ, Skrepnik M, et al. · 2018 · Sports Medicine
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Supports: This review examines strength: longer rests may help, particularly in trained people. For hypertrophy, see the linked 2024 synthesis.
Effect: A small-to-moderate advantage of long rests over short ones, clearer and more consistent for strength than for hypertrophy.
Limitations: Great heterogeneity in protocols and participants' training levels; few studies control for equal total volume between groups with different rest periods.
A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults
Morton RW, Murphy KT, McKellar SR, et al. · 2018 · British Journal of Sports Medicine
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Supports: More daily protein, up to approximately 1.6 g/kg, is associated with greater muscle mass gains with strength training
Effect: The meta-regression found no clear additional benefit above ~1.6 g/kg/day for most people, although the confidence interval does not rule out some benefit up to ~2.2 g/kg/day in some cases — hence the range Horme uses.
Limitations: The population is mostly healthy young adults doing strength training; women and older people are poorly represented; total energy intake is not always controlled between studies.
The development of skeletal muscle hypertrophy through resistance training: the role of muscle damage and muscle protein synthesis
Damas F, Libardi CA, Ugrinowitsch C · 2018 · European Journal of Applied Physiology
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Supports: Muscle soreness (DOMS) is not a good indicator of a session's quality and does not predict greater hypertrophy
Effect: It is not a quantitative meta-analysis: the review argues, synthesizing several studies, that muscle damage is neither necessary nor sufficient for hypertrophy, and that DOMS attenuates with repeated exposure without hypertrophy ceasing to progress.
Limitations: It is a narrative review, not a statistical synthesis; the exact mechanism that best explains hypertrophy is still debated in the literature.
Can drop set training enhance muscle growth?
Schoenfeld BJ, Grgic J · 2018 · Strength and Conditioning Journal
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Supports: Intensity techniques (dropsets, myo-reps, rest-pause) let you accumulate effective stimulus close to failure in less time, with hypertrophy similar to traditional sets but more fatigue per set
Effect: The available studies show comparable hypertrophy between intensity techniques and volume-matched traditional training, with the advantage of a notable time saving; their value lies in taking sets to real failure efficiently, not in beating well-programmed volume.
Limitations: Small, short-term samples; they raise local and systemic fatigue a lot, so they're best saved for the last sets of isolation exercises and for people who already have a base. Horme only SUGGESTS them (never imposes them) and by default only at advanced level.
How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution
Schoenfeld BJ, Aragon AA · 2018 · Journal of the International Society of Sports Nutrition
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Supports: Spreading protein across 3-5 doses of ~0.4 g/kg through the day is a reasonable strategy for maximizing protein synthesis, though the daily total still matters most
Effect: The 0.4 g/kg per meal proposal is a distribution guide, not a utilization ceiling. Later acute studies with 100 g show longer responses; they do not establish an optimal distribution for long-term hypertrophy.
Limitations: Based on acute protein-synthesis studies, not on long-term muscle gains; the effect of distribution is small next to that of the daily total and of training itself. Horme uses it as a distribution suggestion, never as a strict rule.
High-Intensity Resistance and Impact Training Improves Bone Mineral Density and Physical Function in Postmenopausal Women With Osteopenia and Osteoporosis: The LIFTMOR Randomized Controlled Trial
Watson SL, Weeks BK, Weis LJ, Harding AT, Horan SA, Beck BR · 2018 · Journal of Bone and Mineral Research
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Supports: In postmenopausal women with low bone mass, brief, supervised high-intensity resistance and impact training improved bone density and function without relevant adverse events
Effect: 101 women (65 ± 5 years), 8 months, 2 × 30 min/week, 5 × 5 above 85% of 1RM. Lumbar density +2.9% vs −1.2% in controls; femoral neck +0.3% vs −1.9%; improvements in every functional test. A single mild adverse event.
Limitations: A single trial, with close supervision and prior screening, in postmenopausal women. It can't be extrapolated to unsupervised training or to people with previous vertebral fractures.
2019 Canadian guideline for physical activity throughout pregnancy
Mottola MF, Davenport MH, Ruchat SM, et al. · 2018 · British Journal of Sports Medicine
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Supports: Pregnant women without contraindications should stay active combining aerobic and resistance exercise; if lying on the back causes dizziness or discomfort, change position
Effect: Guideline developed with GRADE methodology on a broad systematic review: a moderate net benefit of prenatal physical activity and no harms identified.
Limitations: Population-level recommendations. They don't replace individual assessment when there are obstetric complications.
Magnitude of Muscle Strength and Mass Adaptations Between High-Load Resistance Training Versus Low-Load Resistance Training Associated with Blood-Flow Restriction: A Systematic Review and Meta-Analysis
Lixandrão ME, Ugrinowitsch C, Berton R, et al. · 2018 · Sports Medicine
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Supports: Low-load training with blood flow restriction builds muscle mass similar to high-load training, but less maximal strength
Effect: Similar hypertrophy between high load (>65% 1RM) and low load with BFR (<50% 1RM), regardless of pressure and cuff; greater strength gains with high load.
Limitations: Studies with varied protocols. It's mainly of interest when heavy loading isn't possible; it's not an advantage for those who can load heavy.
Effect of Progressive Calisthenic Push-up Training on Muscle Strength and Thickness
Kotarsky CJ, Christensen BK, Miller JS, Hackney KJ · 2018 · Journal of Strength and Conditioning Research
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Supports: A progressive push-up program with increasingly difficult variations improved bench press strength comparably to bench pressing itself
Effect: 23 moderately trained men, 4 weeks, 3 days/week: both groups improved bench press 1RM; push-up progression improved more in the calisthenics group.
Limitations: Small sample, men only and only 4 weeks; no changes in muscle thickness were detected.
High-Intensity Functional Training (HIFT): Definition and Research Implications for Improved Fitness
Feito Y, Heinrich KM, Butcher SJ, Poston WSC · 2018 · Sports
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Supports: High-intensity functional training is a modality distinct from HIIT, based on varied multi-joint movements and adaptable to any level, with still limited evidence
Effect: Proposes an operational definition of HIFT and reviews the available literature on metabolic and cardiorespiratory adaptations.
Limitations: A definition paper with scarce evidence at the time; results depend heavily on each program's design.
Comparison of Periodized and Non-Periodized Resistance Training on Maximal Strength: A Meta-Analysis
Williams TD, Tolusso DV, Fedewa MV, Esco MR · 2017 · Sports Medicine
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Supports: Planning training in blocks with structured variation of volume and intensity (periodization) produces better strength gains than keeping the same volume/intensity week after week
Effect: Periodized training showed a small-to-moderate advantage over non-periodized training in 1RM gains (an effect size favoring periodization, significant across the body of studies); within periodized models, the variants with more variation (undulating/block) tended to match or beat classic linear periodization.
Limitations: High heterogeneity between studies (different populations, durations and definitions of 'periodized'); the advantage is modest in absolute terms, not a radical leap. Horme uses a simple block model (accumulation → intensification → deload, with a volume ramp of 85%→100% within accumulation and a step back to ~92% in intensification) as a practical coaching convention, not a prescription calibrated to the individual.
Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis
Schoenfeld BJ, Ogborn D, Krieger JW · 2017 · Journal of Sports Sciences
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Supports: More weekly sets per muscle, within a range, produce more hypertrophy
Effect: A positive dose-response relationship: groups with ≥10 sets/week per muscle showed clearly greater muscle mass gains than groups with <5 sets/week.
Limitations: Most of the included studies last only 6–12 weeks; the definition of an "effective set" varies between studies; few highly trained participants; it does not identify an exact individual ceiling (MRV) — which is why Horme treats the range as indicative rather than a fixed limit.
International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine
Kreider RB, Kalman DS, Antonio J, et al. · 2017 · Journal of the International Society of Sports Nutrition
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Supports: Creatine monohydrate improves strength and muscle mass alongside strength training
Effect: Described as the most effective legal ergogenic supplement available for strength training, with consistent strength/power improvements over placebo in the vast majority of the studies synthesized.
Limitations: It is a consensus position covering hundreds of studies, not a single meta-analysis with an aggregate effect size; individual response varies ("responders" versus "non-responders").
The Effect of Menstrual Cycle and Contraceptives on ACL Injuries and Laxity: A Systematic Review and Meta-analysis
Herzberg SD, Motu'apuaka ML, Lambert W, Fu R, Brady J, Guise JM · 2017 · Orthopaedic Journal of Sports Medicine
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Supports: Knee ligament laxity (and possibly the risk of anterior cruciate ligament injury) varies across the menstrual cycle, tending to be somewhat higher around ovulation when estrogen peaks
Effect: An association between the periovulatory/follicular phase and greater laxity/ACL injury risk appeared in several of the included studies, but the overall meta-analysis found low-to-moderate quality evidence and inconsistent results across studies. Horme treats it as a sensible reminder to warm up well and mind your technique on those days, not as an alarm.
Limitations: Low-to-moderate evidence quality by the authors' own assessment; the methods for determining cycle phase vary widely across the original studies; it establishes neither direct causality nor a precise, generalizable effect size.
The 'Critical Power' Concept: Applications to Sports Performance with a Focus on Intermittent High-Intensity Exercise
Jones AM, Vanhatalo A · 2017 · Sports Medicine
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Supports: Critical speed (or power) marks the boundary between the heavy and severe intensity domains, and it can be estimated from two or more maximal efforts of different durations
Effect: The relationship between distance (or work) and time in maximal efforts of approximately 2 to 30 minutes is almost perfectly linear; its slope represents critical velocity/power—the highest sustainable steady-state intensity—and its y-intercept represents finite work capacity above it. Applied to swimming, the same model yields critical swim speed (400 m and 200 m tests).
Limitations: The fit is meaningful only if efforts are TRULY maximal and with well-separated durations: with two similar efforts the line fits two points artificially and yields no insight, even if R² is perfect. Horme enforces duration separation in addition to goodness-of-fit, returning empty if criteria are unmet. Critical velocity is not identical to laboratory-measured lactate threshold, though often proximate.
Exercise and Sports Science Australia (ESSA) position statement on exercise prescription for the prevention and management of osteoporosis
Beck BR, Daly RM, Singh MA, Taaffe DR · 2017 · Journal of Science and Medicine in Sport
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Supports: To prevent and manage osteoporosis, bone responds to impact activities and high-intensity progressive resistance training; loaded spinal flexion is not recommended
Effect: Position statement based on animal and human trials: impact and high-intensity progressive resistance training, plus strength, balance and mobility to reduce falls; prescription must be individualized to fracture risk.
Limitations: Consensus document. Modifications for osteoarthritis, frailty or previous fractures require professional assessment.
Hypertrophic Effects of Concentric vs. Eccentric Muscle Actions: A Systematic Review and Meta-analysis
Schoenfeld BJ, Ogborn DI, Vigotsky AD, Franchi MV, Krieger JW · 2017 · Journal of Strength and Conditioning Research
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Supports: Eccentric actions tend to produce somewhat more hypertrophy than concentric ones, although the difference didn't reach statistical significance
Effect: 15 studies. Effect size difference favoring eccentrics of 0.25 (95% CI −0.03 to 0.52; p = 0.076).
Limitations: Not significant: it's a trend, not demonstrated superiority. In practice, controlling the lowering is sensible; removing the concentric phase isn't.
Preserving Healthy Muscle during Weight Loss
Cava E, Yeat NC, Mittendorfer B · 2017 · Advances in Nutrition
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Supports: During weight loss, strength exercise helps preserve muscle mass and also improves strength and function
Effect: Diet-induced weight loss reduces muscle mass; aerobic and resistance exercise help preserve it, and resistance exercise also improves strength. Adequate, not excessive, protein is recommended.
Limitations: Narrative review focused on people with obesity. It doesn't quantify an optimal training dose.
Application of the Repetitions in Reserve-Based Rating of Perceived Exertion Scale for Resistance Training
Helms ER, Cronin J, Storey A, Zourdos MC · 2016 · Strength and Conditioning Journal
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Supports: Adjusting your proximity-to-failure target (RIR) according to how you feel that day is a valid way of autoregulating training
Effect: This is not a meta-analysis with an aggregate effect size: it is a methodological paper validating the RIR/RPE scale as an autoregulation tool — it describes how training further from failure on worse days and closer on better days lets you match the actual load to each session's actual performance.
Limitations: RIR perception varies with experience (beginners estimate it worse than advanced lifters); it is a practical autoregulation tool, not a quantitative finding about exactly how much it improves results compared with a fixed RIR.
The training—injury prevention paradox: should athletes be training smarter and harder?
Gabbett TJ · 2016 · British Journal of Sports Medicine
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Supports: ACWR describes relative workload changes. Historical injury associations have statistical and conceptual limitations; they do not validate a universal safe range or independently predict individual injury.
Effect: It synthesizes studies across several team sports where an acute:chronic workload ratio (ACWR) between ~0.8 and 1.3 (the 'sweet spot') was associated with fewer injuries than ratios above ~1.5, even at the SAME accumulated chronic load — the pattern of progression matters, not just the total.
Limitations: Most of the source studies are in team sports (rugby, football) with load measured by GPS/distance covered, not strength training with sRPE; the exact bands (0.8/1.3/1.5) are indicative and debated in the subsequent literature, not an exact and universal physiological limit.
The Triathlete's Training Bible (4th edition) — threshold field test protocol
Friel J · 2016 · VeloPress (training manual)
Supports: The average heart rate of the last 20 minutes of a 30-minute time trial is a practical approximation of threshold heart rate, and it serves to define individualized training zones
Effect: Zones defined as a percentage of threshold HR (Z1 <85%, Z2 85–89%, Z3 90–94%, Z4 95–99%, Z5 ≥100%) anchor boundaries to measured personal data rather than age-predicted maximal HR, which carries standard error of ±7 bpm and shifts all zones simultaneously.
Limitations: It is a practical endurance training convention, not a laboratory measurement of lactate threshold or second ventilatory threshold; the protocol itself assumes steady, well-regulated effort, and a poorly executed test (flying and dying) produces a false threshold. Threshold shifts with training: Horme marks thresholds older than six months as stale.
Guide to creating a front of pack (FoP) nutrition label for pre-packed products sold through retail outlets
Department of Health and Social Care · Food Standards Agency · Devolved administrations (United Kingdom) · 2016 · Official UK Government guidance
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Supports: A food is considered HIGH in sugars (>22.5 g/100 g), saturated fat (>5 g/100 g), total fat (>17.5 g/100 g) or salt (>1.5 g = 600 mg of sodium/100 g); in drinks the four cut-offs are roughly half
Effect: This is not an intervention study: it establishes Front-of-Pack traffic light color criteria. Horme uses the RED boundary as the 'high in ...' threshold for warning badges, since Regulation 1924/2006 specifies 'low' but never defines 'high'.
Limitations: It is a consumer labeling guide, not a clinical standard, with consensus thresholds designed to steer purchasing rather than evaluate individual diets. It applies to TOTAL sugars without distinguishing added from intrinsic fruit/dairy sugars. Consequently, Horme does NOT implement Colombian warning seals (Res. 810/2021 & 2492/2022), which penalize free sugars and would flag a banana.
Factors Modulating Post-Activation Potentiation of Jump, Sprint, Throw, and Upper-Body Ballistic Performances: A Systematic Review with Meta-Analysis
Seitz LB, Haff GG · 2016 · Sports Medicine
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Supports: A prior conditioning activity slightly enhances jumping and throwing and moderately enhances sprinting, more so in strong people and with longer recoveries
Effect: 47 studies and 1,954 participants. Small effect on jumps (ES 0.29), throws (0.26) and upper-body ballistics (0.23), moderate on sprints (0.51). Larger in stronger people and with long (ES 0.44–0.49) versus short recoveries (0.17).
Limitations: Acute, small effect that depends heavily on strength level. Optimal timings vary between people.
The Importance of Muscular Strength in Athletic Performance
Suchomel TJ, Nimphius S, Stone MH · 2016 · Sports Medicine
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Supports: Greater muscular strength is associated with better jumping, sprinting and change of direction, greater potentiation capacity and lower injury risk
Effect: Review concluding that there seems to be no substitute for greater muscular strength to improve a wide range of general and sport-specific skills.
Limitations: Much of the evidence is associative, not causal; transfer depends on the sport and the starting level.
Sleep and Athletic Performance: The Effects of Sleep Loss on Exercise Performance, and Physiological and Cognitive Responses to Exercise
Fullagar HHK, Skorski S, Duffield R, et al. · 2015 · Sports Medicine
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Supports: Sleeping too little harms physical performance and recovery
Effect: Sleep deprivation more consistently harms prolonged submaximal performance and mood/perception of effort than one-off maximal strength, although the effect varies a lot between studies.
Limitations: Great heterogeneity in how "sleep deprivation" is defined and measured across studies; many involve acute laboratory deprivation rather than mild chronic restriction (the more common real-life scenario).
Reference standards for cardiorespiratory fitness measured with cardiopulmonary exercise testing: data from the Fitness Registry and the Importance of Exercise National Database (FRIEND)
Kaminsky LA, Arena R, Myers J · 2015 · Mayo Clinic Proceedings
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Supports: A VO₂max can only be interpreted by comparing it with the population of the same age and sex: the FRIEND registry provides contemporary reference percentiles
Effect: Percentiles of measured VO2max from treadmill cardiopulmonary exercise tests, by sex and age decade, across tens of thousands of tests in healthy adults. The median declines approximately 1% per year starting from the third decade, making the same absolute value mean very different things at age 25 versus age 55.
Limitations: The sample is from US laboratories and is not a random sample of the general population, so percentiles may shift in other populations. Horme interpolates between decades and ROUNDS the percentile to multiples of 5, always showing it alongside its category: the table serves to position within a band, not to claim an exact percentile. And the VO2max compared against it is rarely measured on a treadmill: if it comes from a formula, method error can span an entire category, and the app states this.
Effectiveness of High-Intensity Interval Training (HIT) and Continuous Endurance Training for VO2max Improvements: A Systematic Review and Meta-Analysis of Controlled Trials
Milanović Z, Sporiš G, Weston M · 2015 · Sports Medicine
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Supports: High-intensity interval training improves VO₂max more than moderate-intensity continuous training
Effect: Across 28 studies in healthy adults, both modalities clearly improve VO2max versus no training; in direct head-to-head comparison, interval training delivered an additional gain of approximately 1.2 ml/kg/min over continuous exercise. Effect size is larger in those starting from lower baselines.
Limitations: Pooled protocols are highly heterogeneous (interval durations, intensities, session volumes), so mean difference obscures disparate training dynamics. Most trials span 6 to 12 weeks with inadequate reporting of adherence or injury rates—domains where steady-state conditioning typically prevails in real-world adherence. Horme prescribes both and reserves high-intensity intervals for those with established aerobic conditioning.
Strategies to Improve Running Economy
Barnes KR, Kilding AE · 2015 · Sports Medicine
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Supports: Running economy can be improved with strength work, short hills and fast intervals with full recovery, and it explains performance beyond what VO₂max explains
Effect: The review summarizes evidence-based interventions to improve running economy: resistance and plyometric training, hill intervals, short high-velocity sprints, and accumulated running volume. Among runners with similar VO2max, economy disparities explain much of the variance in race performance.
Limitations: Narrative review of heterogeneous studies with divergent methodologies and economy assessment protocols; effect sizes are not directly comparable. Running economy is highly individual, influenced by biomechanics and footwear, and laboratory gains do not always translate linearly to race times.
Effect of Repetition Duration During Resistance Training on Muscle Hypertrophy: A Systematic Review and Meta-Analysis
Schoenfeld BJ, Ogborn DI, Krieger JW · 2015 · Sports Medicine
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Supports: With repetitions lasting 0.5 to 8 seconds, hypertrophy is similar; very slow repetitions (over 10 s) appear inferior
Effect: 8 studies with sets to failure: similar results between 0.5 and 8 s per rep; signs of worse results above 10 s.
Limitations: Few studies, and the super-slow data come from very few controlled trials, so its inferiority isn't definitive.
Recommendations for natural bodybuilding contest preparation: resistance and cardiovascular training
Helms ER, Fitschen PJ, Aragon AA, Cronin J, Schoenfeld BJ · 2015 · Journal of Sports Medicine and Physical Fitness
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Supports: In natural bodybuilding contest preparation it's advisable to periodize, train each muscle at least twice a week, do most reps between 6 and 12 and reserve failure for single-joint exercises
Effect: Recommends 40–70 reps per muscle group per session, 1–3 min rests, controlled tempos and the least cardio that achieves fat loss.
Limitations: A recommendations review predating recent volume meta-analyses. The figures are starting points for bodybuilders, not universal rules.
Weightlifting Pulling Derivatives: Rationale for Implementation and Application
Suchomel TJ, Comfort P, Stone MH · 2015 · Sports Medicine
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Supports: Weightlifting derivatives without the catch (pulls, high pulls, jump shrugs) teach explosive triple extension with less technical complexity and may stimulate as much as the full lifts
Effect: Review justifying the use of catch-free derivatives in athletes who don't compete in weightlifting.
Limitations: Authors' review; direct longitudinal comparisons between derivatives and full lifts are lacking.
Bench Press and Push-up at Comparable Levels of Muscle Activity Results in Similar Strength Gains
Calatayud J, Borreani S, Colado JC, Martin F, Tella V, Andersen LL · 2015 · Journal of Strength and Conditioning Research
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Supports: With comparable muscle activation, elastic-band push-ups and the bench press produce similar strength gains
Effect: 30 students with advanced experience, 5 weeks at 6RM: similar improvements in 1RM and 6RM (13.65–22.21%) in the bench press and band push-ups.
Limitations: Small sample and short period. What equalizes the result is matching relative load, not the push-up itself.
Metabolic adaptation to weight loss: implications for the athlete; plus adaptive thermogenesis literature
Trexler ET, Smith-Ryan AE, Norton LE · 2014 · Journal of the International Society of Sports Nutrition
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Supports: During sustained weight loss, energy expenditure drops more than the weight change alone would predict (adaptive thermogenesis), so the rate of loss tends to SLOW DOWN over time
Effect: Resting and activity energy expenditure fall below what the loss of mass predicts; the effect is larger with aggressive deficits and long periods. Practical consequence: extrapolating your current rate of loss linearly UNDERESTIMATES the real time to reach a low body fat %. Horme flags this on every time-to-body-fat estimate.
Limitations: The size of the adaptation varies a lot between people and is hard to measure precisely outside a lab; Horme doesn't model it quantitatively (it has no validated intake record), it only uses it as a qualitative warning that the real time is usually longer than the linear projection.
Position statement on youth resistance training: the 2014 International Consensus
Lloyd RS, Faigenbaum AD, Stone MH, et al. · 2014 · British Journal of Sports Medicine
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Supports: Strength training in children and adolescents is safe and beneficial when supervised by qualified staff and progressed gradually with a focus on technique
Effect: International consensus endorsed by sports medicine, pediatric and exercise science organizations.
Limitations: Expert position statement, not a meta-analysis. It doesn't set universal maximal loads: supervision and technical maturity come first.
Training adaptation and heart rate variability in elite endurance athletes: opening the door to effective monitoring
Plews DJ, Laursen PB, Stanley J, et al. · 2013 · Sports Medicine
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Supports: HRV can inform autonomic regulation and training trends. It does not directly measure recovery or diagnose overtraining; consider measurement method, baseline and other signals.
Effect: HRV tends to rise with good recovery/adaptation and fall with fatigue or overload, but the relationship is neither linear nor universal — it depends heavily on each person's baseline (which is why Horme compares it against your own rolling average, never against an absolute value).
Limitations: Great individual variability and influence from factors unrelated to training (stress, alcohol, illness, breathing pattern); most studies were done in elite endurance athletes, not the general gym population.
The behavior change technique taxonomy (v1) of 93 hierarchically clustered techniques
Michie S, Richardson M, Johnston M, et al. · 2013 · Annals of Behavioral Medicine
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Supports: There is a standardized vocabulary of behavior change techniques (self-monitoring, feedback, reinforcement, implementation planning…) that allows you to describe precisely what makes an intervention work
Effect: It does not measure an effect: it is an international consensus process (Delphi method) defining and classifying 93 behavior change techniques (BCTs) so that interventions can be described, replicated and compared consistently — Horme draws on several of these techniques (self-monitoring, feedback on behavior, if-then planning, reinforcement) without claiming to implement them all.
Limitations: It is a classification framework, not evidence that each technique works on its own; which combination of BCTs works best depends heavily on the context and the person.
The Oslo Sports Trauma Research Center questionnaire on health problems: a new approach to prospective monitoring of illness and injury in elite athletes
Clarsen B, Rønsen O, Myklebust G, Flørenes TW, Bahr R · 2013 · British Journal of Sports Medicine
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Supports: Asking periodically about current discomfort/pain (not just about injuries that have already stopped you) detects overuse problems far earlier than waiting for an injury that prevents training altogether
Effect: The OSTRC questionnaire, applied weekly, picked up far more overuse complaints (tendinopathies, progressive joint pain) than traditional medical records, which only count injuries severe enough to prompt a consultation — most overuse problems NEVER get recorded if you only count injuries that stop you training.
Limitations: Designed and validated in elite athletes with regular medical follow-up; Horme adapts the core idea (asking about current pain periodically instead of only reacting to injuries) in a simplified form and without medical supervision — a check-in in the app is no substitute for assessment by a physiotherapist or sports physician.
Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises
Wilson JM, Marin PJ, Rhea MR, Wilson SMC, Loenneke JP, Anderson JC · 2012 · Journal of Strength and Conditioning Research
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Supports: Combining cardio with strength training can blunt strength and hypertrophy gains (the 'interference effect'), but the magnitude depends on how they are combined: cardio volume, its intensity, the modality and the order
Effect: Interference with hypertrophy and strength was greater the more frequent and longer the aerobic work, and greater with running than with cycling (more muscle damage). Strength training alone, compared with concurrent training, showed better power and hypertrophy gains; with moderate aerobic volumes the effect is small.
Limitations: A 2012 meta-analysis with studies highly heterogeneous in duration, participant level, and protocols; it does not isolate nutrition or actual hourly separation between sessions well. It is retained as historical context, but Horme's current prescription uses the updated review by Schumann et al. 2022 and does not impose a universal hourly separation.
The 10-20-30 training concept improves performance and health profile in moderately trained runners
Gunnarsson TP, Bangsbo J · 2012 · Journal of Applied Physiology
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Supports: The 10-20-30 format (blocks of 30 s easy, 20 s moderate and 10 s all-out) improves 5 km performance and health markers while reducing total training volume
Effect: In moderately trained runners, seven weeks of the 10-20-30 format—alongside ~50% training volume reduction—improved 1,500 m times by ~21 s and 5K times by ~48 s, while lowering blood pressure and LDL cholesterol, versus no changes in habitual training controls.
Limitations: Small sample, unblinded, and limited to a single profile (already conditioned recreational runners). Control subjects maintained habitual training rather than a load-matched alternate protocol, so gains may partly reflect novel stimulus response. Does not address multi-month maintenance outcomes.
Exercise Order in Resistance Training
Simão R, de Salles BF, Figueiredo T, Dias I, Willardson JM · 2012 · Sports Medicine
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Supports: Where an exercise sits within the session changes how you perform in it: placed at the end you complete fewer reps (and hold less load) than placed at the start, and the drop is larger when what comes before works the same muscles
Effect: Reviewed trials consistently show that exercises performed late in a workout suffer a 10–25% repetition drop versus early execution, with decrements concentrated in movements preceded by work targeting the same muscle group. The practical takeaway—prioritize key goals and heavy multi-joint movements early—aligns with systematic reviews and the ACSM consensus.
Limitations: Most are acute single-session studies in small samples of trained young males; long-term adaptations in hypertrophy and strength are less definitive than acute repetition declines. Exact percentage loss depends on exercise, rest interval, and fitness: Horme applies it as a BOUNDED ESTIMATE to compare sessions, never as a raw performance diagnostic.
Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes
Garthe I, Raastad T, Refsnes PE, et al. · 2011 · International Journal of Sport Nutrition and Exercise Metabolism
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Supports: A more moderate calorie deficit, alongside more protein, preserves lean mass better than an aggressive deficit
Effect: The slower weight-loss group preserved significantly more lean mass than the rapid-loss group, with similar fat loss between the two groups.
Limitations: A small sample (elite athletes, ~24 people) and a single study, not a meta-analysis — Horme's rate ranges rest on this finding alongside the general consensus of the body composition literature, not on this trial alone.
The effect of an upper-body agonist-antagonist resistance training protocol on volume load and efficiency
Robbins DW, Young WB, Behm DG, Payne WR · 2010 · Journal of Strength and Conditioning Research
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Supports: Alternating exercises for antagonist groups (a superset) lets you do the same work in considerably less time, without losing volume load
Effect: The agonist-antagonist protocol maintained a volume load similar to the traditional approach in roughly half the time, meaning far greater efficiency per minute of session.
Limitations: An acute study (comparing sessions, not weeks of adaptation) and only in the upper body, with few trained participants. The ~35% saving Horme estimates is a conservative programming convention, not this study's exact number; in heavy exercises with complicated setups the real saving may be smaller.
A meta-analysis of motivational interviewing: Twenty-five years of empirical studies
Lundahl BW, Kunz C, Brownell C, Tollefson D, Burke BL · 2010 · Research on Social Work Practice
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Supports: Motivational interviewing (exploring and reinforcing the person's own motivation rather than imposing external reasons) improves adherence to health behavior change
Effect: A small-to-moderate but consistent effect favoring motivational interviewing over no treatment and over other active treatments, replicated across multiple health domains (not just addiction, its origin).
Limitations: High heterogeneity between studies in how it is applied and how fidelity to the technique is measured; Horme does NOT offer real motivational interviewing (that requires a trained professional) — it only applies its core logic (the importance/confidence rule, reflecting rather than lecturing) in a simplified, automated way.
What is Best Practice for Training Intensity and Duration Distribution in Endurance Athletes?
Seiler S · 2010 · International Journal of Sports Physiology and Performance
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Supports: A distribution dominated by easy training can be useful. The 80/20 split is a guide; polarized training has no demonstrated universal superiority over other well-designed models.
Effect: The observation is consistent across high-level endurance athletes in various disciplines: ~75–80% of sessions at low intensity (below first ventilatory threshold) and ~15–20% at high intensity, with very little time in the middle zone. Trials directly comparing polarized versus threshold distribution find slightly greater improvements with polarized, but with small sample sizes over periods of only a few weeks.
Limitations: Evidence comes mostly from already trained athletes and observational studies of training habits, not randomized trials. In beginners, and base-building phases, a pyramidal distribution yields equivalent results. Seiler himself cautions that 80/20 is a description of practice, not a prescription with a magic number. Horme classifies the breakdown and comments on it; it does NOT claim that any one model is mandatory.
Progression Models in Resistance Training for Healthy Adults (ACSM Position Stand)
Ratamess NA, Alvar BA, Evetoch TK, et al. (American College of Sports Medicine) · 2009 · Medicine & Science in Sports & Exercise
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Supports: Before your working sets, a few ramp-up sets with increasing load prepare the neuromuscular system without accumulating significant fatigue
Effect: This is not a trial measuring a quantified effect of ramp warm-ups specifically: it is a consensus position reviewing the strength training prescription literature and recommending 1–2+ ramp-up sets with progressive loads before the real work as general good practice.
Limitations: The exact percentages Horme uses (40/60/80% of your working weight) are a common practical convention in strength coaching, not a protocol literally prescribed by this consensus position; the real benefit varies with the exercise, the person and how much general warm-up you have already done.
A Behavior Model for Persuasive Design
Fogg BJ · 2009 · Proceedings of the 4th International Conference on Persuasive Technology (ACM)
Supports: Anchoring a tiny behavior to a routine you already do, and celebrating it immediately, is an effective way of establishing a new habit
Effect: It is not a trial with an effect size: it proposes that behavior occurs when Motivation, Ability and a Trigger coincide at the same instant (B=MAP) — hence making the behavior VERY small (low ability demand) and anchoring it to an existing trigger reduces dependence on motivation, the least reliable of the three.
Limitations: It is a conceptual model, not a synthesis of controlled trials; its empirical validation comes mostly from the author's own programs (Tiny Habits), with fewer independent replications than other techniques on this list.
Cardiorespiratory Fitness as a Quantitative Predictor of All-Cause Mortality and Cardiovascular Events in Healthy Men and Women
Kodama S, Saito K, Tanaka S, Maki M, Yachi Y, Asumi M, et al. · 2009 · JAMA
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Supports: Cardiorespiratory fitness (VO₂max) is one of the best-supported predictors of mortality and cardiovascular events: each additional MET is associated with a substantial reduction in risk
Effect: For each 1 MET (3.5 ml/kg/min) increase in maximal cardiorespiratory fitness, the risk of all-cause mortality and coronary heart disease/cardiovascular events was approximately 13% and 15% lower, respectively.
Limitations: Meta-analysis of cohort studies: association, not causality, and cardiorespiratory fitness has a significant genetic component in addition to trainability. Cohorts consisted of healthy adults, so effect size does not directly translate to populations with established disease.
Determining Variables of Plyometric Training for Improving Vertical Jump Height Performance: A Meta-Analysis
de Villarreal ES, Kellis E, Kraemer WJ, Izquierdo M · 2009 · Journal of Strength and Conditioning Research
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Supports: Plyometric training improves vertical jump height, especially combining jump types and with programs longer than 10 weeks; adding load brings no extra benefit
Effect: 56 studies and 225 effect sizes. Greater improvement with more than 10 weeks and 20 sessions, high-intensity programs and combined jump types (squat, countermovement and drop jumps); no extra benefit with added weight.
Limitations: Outcome focused on vertical jump; transfer to other tasks depends on the sport. Populations and load control vary widely between studies.
Comprehensive warm-up programme to prevent injuries in young female footballers: cluster randomised controlled trial
Soligard T, Myklebust G, Steffen K, et al. · 2008 · BMJ
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Supports: A neuromuscular warm-up program reduced some injuries in adolescent female football players. The size and outcomes of that trial cannot automatically be transferred to every warm-up or sport.
Effect: The warm-up program (FIFA 11+) cut total injuries by roughly a third, and severe and overuse injuries by even more, compared with the control group's usual warm-up, in a large cluster trial (whole teams, not individuals).
Limitations: Studied in youth women's football with a sport-specific program (balance, plyometrics, running), not in gym strength training; the mechanism (better neuromuscular control) generalizes, but the exact size of the effect in weightlifting isn't as well established.
Effects of Tapering on Performance
Bosquet L, Montpetit J, Arvisais D, Mujika I · 2007 · Medicine & Science in Sports & Exercise
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Supports: Markedly reducing training volume in the 1–3 weeks before an important date (competition, a max test), while maintaining or slightly raising intensity, improves performance compared with continuing to train at the same volume
Effect: Tapering improved performance by around 3% on average compared with maintaining the usual load — a progressive, non-linear volume reduction (cutting volume a lot while maintaining intensity) was the strategy with the best evidence among the variants compared.
Limitations: Most of the original studies are in endurance sports/swimming, not pure strength — the exact magnitude may differ in strength training. Horme applies the same principle (drop volume, maintain/raise intensity) in its 2-week 'Peak' model (taper to 70%, peak at 40% of prescribed volume) as a practical convention, not a prescription calibrated to your specific sport.
Aerobic high-intensity intervals improve VO2max more than moderate training
Helgerud J, Høydal K, Wang E, Karlsen T, Berg P, Bjerkaas M, et al. · 2007 · Medicine & Science in Sports & Exercise
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Supports: Long high-intensity intervals (4×4 min at 90–95 % of maximum heart rate) raise VO₂max more than the same volume of moderate continuous work
Effect: With energy expenditure matched between groups, both high-intensity protocols (15/15 and 4×4 min) improved VO2max by approximately 5.5% and 7.2% over eight weeks, versus non-significant changes in moderate-intensity groups. Stroke volume increased ~10% in interval cohorts.
Limitations: Small sample (~40 moderately trained young men) and eight-week duration: says nothing about long-term sustainability or injury risk under prolonged adoption. A protocol demanding 90–95% of maximal HR requires a prior aerobic base; Horme does not offer this workout below advanced tier and withdraws it when acute-to-chronic training balance is depressed.
Effects of tapering on performance: a meta-analysis
Bosquet L, Montpetit J, Arvisais D, Mujika I · 2007 · Medicine & Science in Sports & Exercise
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Supports: Reducing training volume while maintaining intensity and frequency during the two weeks before a competition improves performance
Effect: Across 27 studies, mean performance improvement following a taper was approximately 2–3%. Optimal parameters identified: 41–60% volume reduction, ~2-week duration, and UNCHANGED intensity and session frequency.
Limitations: Pooled trials primarily involved conditioned laboratory athletes with heterogeneous performance testing modalities. Absolute effect size is modest and applies to those entering with accumulated chronic training load: tapering on low training volume confers no benefit. Horme incorporates tapering exclusively in race-specific periodized plans.
Implementation intentions and goal achievement: A meta-analysis of effects and processes
Gollwitzer PM, Sheeran P · 2006 · Advances in Experimental Social Psychology
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Supports: Planning a specific situation and your exact response to it in advance ('if X happens, then I will do Y') increases the probability of meeting a goal compared with merely intending it
Effect: A medium-to-large and consistent effect on goal achievement (d≈0.65 aggregated in the original meta-analysis) compared with simply setting a general goal — the if-then plan delegates the decision to the moment of the cue, instead of depending on willpower in real time.
Limitations: The effect varies with goal difficulty and with whether the person already genuinely intends to change; it works less well if the chosen 'trigger situation' is vague or infrequent in the person's real life.
Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance
Gibala MJ, Little JP, van Essen M, Wilkin GP, Burgomaster KA, Safdar A, et al. · 2006 · The Journal of Physiology
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Supports: Very short sprint intervals (a few minutes of total work per session) produce muscular and performance adaptations comparable to much larger volumes of continuous work
Effect: Two weeks of sprint interval training (~2.5 minutes of work per session with extended recovery) produced skeletal muscle oxidative capacity increases and time-trial performance improvements equivalent to continuous endurance training at ten-fold higher volume.
Limitations: Very short duration (two weeks), small sample of active young adults, and cycle ergometer protocol with truly all-out sprint efforts, which are acutely strenuous and show low real-world adherence outside the lab. Equivalence was established via muscle biopsies and time-trial performance, not long-term health outcomes. Horme provides it as a time-crunched option, not a substitute for aerobic base building.
Regulation (EC) No 1924/2006 on nutrition and health claims made on foods (and its amended annex)
European Parliament and Council of the European Union · 2006 · Official Journal of the European Union L 404
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Supports: The claims “high in protein” (≥20 % of energy), “source of protein” (≥12 %), “high in fiber” (≥6 g/100 g), “low in fat” (≤3 g/100 g), “low in sugars” (≤5 g/100 g) and “low in sodium” (≤120 mg/100 g) have legally defined thresholds, not matters of opinion
Effect: This is not an empirical study: it defines the THRESHOLDS under which food products may carry specific nutrition claims. Horme adopts them directly for positive nutrition diary badges (M.foodFlags, 13-meals.js). Liquid thresholds per 100 ml are half those of solid foods for fats and sugars.
Limitations: This is European regulation while Horme launches in Colombia: it carries no legal mandate here, but provides a published, verifiable standard over arbitrary metrics. It does NOT define 'high in' for sugar, salt, or saturated fat—for which UK Front-of-Pack traffic lights (uk-fsa-fop) are used. And metrics apply per 100 g, making them inapplicable to foods logged per unit.
Relapse prevention for alcohol and drug problems: That was Zen, this is Tao
Witkiewitz K, Marlatt GA · 2004 · American Psychologist
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Supports: A one-off slip (a lapse) is not the same as a full relapse; treating it as a total failure ('I have broken it now, so why bother') is what most predicts giving up altogether
Effect: It is not a meta-analysis with an aggregate figure: it synthesizes that anticipating high-risk situations and having a coping plan reduces the probability of a one-off slip escalating into complete abandonment (the model describes this jump as the 'abstinence violation effect').
Limitations: Developed and validated mostly in addiction (alcohol/drugs); extrapolating it to training adherence is a reasonable application but not a proven finding in that specific context.
A comparison of linear and daily undulating periodized programs with equated volume and intensity for strength
Rhea MR, Ball SD, Phillips WT, Burkett LN · 2002 · Journal of Strength and Conditioning Research
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Supports: This study compared linear and daily undulating periodization with matched volume and intensity. It should not be described as a test of weekly variation or universal superiority.
Effect: The undulating periodization group (daily/weekly variation of volume and intensity) achieved greater 1RM gains in the squat and bench press than the classic linear periodization group, with total volume and intensity equated between groups.
Limitations: A single trial with a small sample (not a meta-analysis) and a short duration (~12 weeks) — the advantage of the undulating variant over linear does not replicate consistently across the subsequent literature; Horme offers the undulating model as a valid ALTERNATIVE to linear (alternating volume/intensity weeks), not as the objectively superior model.
A New Approach to Monitoring Exercise Training
Foster C, Florhaug JA, Franklin J, et al. · 2001 · Journal of Strength and Conditioning Research
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Supports: The perceived effort of a session multiplied by its duration is a valid way of quantifying training load without heart rate sensors
Effect: The sRPE method (session RPE × minutes) correlated well with heart-rate-based load methods (TRIMP) in the original study.
Limitations: Session RPE is subjective and varies with each person's experience; in Horme it is approximated as the average per-set RPE you logged that day (excluding warm-ups) — if you do not log RPE on your sets, that day contributes no real load to the model, and it is never filled in with an invented value.
Coyle, E.F. & González-Alonso, J. Cardiovascular drift during prolonged exercise: new perspectives
Coyle EF, González-Alonso J · 2001 · Exercise and Sport Sciences Reviews
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Supports: In a continuous aerobic effort, a heart rate that rises in the second half at the same pace (cardiac drift) indicates the intensity is above steady state, or that aerobic base, heat or hydration is the issue
Effect: During prolonged exercise at constant intensity, heart rate progressively rises while stroke volume declines. The primary determinants identified are hyperthermia and progressive dehydration, leading to reduced plasma volume. The magnitude of cardiovascular drift is inversely related to training status and relative effort intensity.
Limitations: The review describes the physiological phenomenon; the practical 5% threshold that Horme uses to validate a session does NOT come from this paper—it is an endurance training convention. The metric does not distinguish between its three possible causes, and the app states this explicitly: it is not a diagnosis. It does not apply to interval workouts, where the second half is harder by design.
Heart-rate recovery immediately after exercise as a predictor of mortality
Cole CR, Blackstone EH, Pashkow FJ, Snader CE, Lauer MS · 1999 · New England Journal of Medicine
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Supports: A heart-rate drop of ≤12 bpm at one minute was associated with mortality in the studied clinical protocol. The cutoff depends on recovery protocol and does not diagnose risk from arbitrary watch readings.
Effect: In a cohort of over 2,400 adults referred for exercise testing, a heart rate reduction of 12 beats or fewer in the first minute of recovery (with ACTIVE walking recovery) was associated with several-fold higher six-year mortality risk, adjusting for exercise capacity, myocardial perfusion, and ECG changes. It is interpreted as a reflection of vagal reactivation.
Limitations: Clinical cohort (individuals referred for stress testing), not general population, and association, not causality. The value depends STRONGLY on protocol: stopping cold or lying down yields greater drops than walking, so the 12 bpm cutoff is not directly transferable to measurements taken differently. Horme calculates the drop from peak on a real trace, cautions that the original protocol involved walking recovery, and presents the figure as a TREND across your sessions, never as a diagnosis.
Monitoring training in athletes with reference to overtraining syndrome
Foster C · 1998 · Medicine & Science in Sports & Exercise
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Supports: Training with the same load every day (little variation) is associated with more risk of overtraining/illness than the same total load spread out more variably
Effect: In the swimming team studied, the periods with the highest monotony (mean daily load ÷ standard deviation) and strain (total load × monotony) coincided with more episodes of illness/overtraining symptoms than periods of similar total load but more day-to-day variation.
Limitations: An observational study in an elite swimming team, not a controlled trial; load was measured with sRPE (session RPE × duration), the same method Horme uses — but the sample size is small and the finding is correlational, not causal.
Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max
Tabata I, Nishimura K, Kouzaki M, Hirai Y, Ogita F, Miyachi M, Yamamoto K · 1996 · Medicine & Science in Sports & Exercise
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Supports: The protocol of 8 sets of 20 s at supramaximal intensity with 10 s rest improves aerobic and anaerobic capacity at the same time
Effect: Over six weeks, the intermittent protocol (7–8 sets of 20 s at ~170% VO2max with 10 s rest, five days per week) increased VO2max by ~7 ml/kg/min and anaerobic capacity by 28%, whereas moderate continuous training yielded comparable VO2max gains without improving anaerobic capacity.
Limitations: Very small cohort of active male students, on cycle ergometers and at an intensity (170% VO2max) rarely replicated outside laboratories: gym classes using that name are not this protocol. Horme outlines the authentic protocol and its actual intensity demands, offering it exclusively above intermediate status.
Energy intakes are higher during the luteal phase of ovulatory menstrual cycles
Barr SI, Janelle KC, Prior JC · 1995 · The American Journal of Clinical Nutrition
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Supports: This study observed higher energy intake in the luteal phase of ovulatory cycles. It does not by itself measure resting expenditure changes or justify fixed calorie additions by calendar.
Effect: Spontaneous energy intake averaged ~2–7% higher in the luteal phase than in the follicular phase in the group studied (on the order of 90–300 kcal/day in women of average weight) — consistent with the literature on progesterone's thermogenic effect on basal metabolism. Horme uses a conservative fixed figure (+150 to +200 kcal/day) within that range, not a value measured on you.
Limitations: Observational study in a small group of women; the exact magnitude varies a lot between people and cycles, and depends on whether the cycle was ovulatory; Horme doesn't measure your real energy expenditure (there's no food diary validated by calorimetry), so this adjustment is a population ESTIMATE applied by phase, not an individual recalibration.
Stages and processes of self-change of smoking: toward an integrative model of change
Prochaska JO, DiClemente CC · 1983 · Journal of Consulting and Clinical Psychology
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Supports: Changing a health habit passes through recognizable stages (precontemplation, contemplation, preparation, action, maintenance), and the useful strategy depends on which one you are in
Effect: An original observational study (not a controlled trial): it identified that people quitting smoking on their own passed through the same recognizable stages, and that the change processes they used varied systematically by stage.
Limitations: The original model is about smoking, not exercise; assigning a stage from just 2 questions (importance/confidence), as Horme does, is a practical simplified approximation, not the validated staging instrument (e.g. URICA) a clinical study would use.
Daniels, J. & Gilbert, J. Oxygen Power: Performance Tables for Distance Runners
Daniels J, Gilbert J · 1979 · Oxygen Power (monograph)
Supports: The time in a run of 5 to 60 minutes allows a runner's aerobic power (VDOT) to be estimated, and from it the easy, marathon, threshold, interval and repetition training paces
Effect: The pair of equations (oxygen cost of velocity, and sustainable percentage of VO2max over a given time) closely reproduces distance running performance tables and serves as the most widely used pace prescription benchmark in run coaching. Horme calibrated its intensity percentages against published tables at VDOT 38, 50, and 60.
Limitations: It is a performance model, not a laboratory measurement: VDOT is not measured VO2max and can differ by several ml/kg/min. It assumes a maximal effort and a runner trained FOR that distance, so extrapolating from a 5K to a marathon describes the aerobic engine, not specific endurance. Outside the 5-to-60-minute window, the model ceases to describe effort, and Horme returns empty rather than a number.
A systems model of training for athletic performance
Banister EW, Calvert TW, Savage MV, Bach T · 1975 · Australian Journal of Sports Medicine
Supports: Daily training load can be summarized as a 'chronic' load (fitness, decaying slowly) and an 'acute' load (fatigue, decaying quickly) to estimate your relative balance
Effect: The original impulse-response model (two exponentials with time constants of ~42 days for the fitness component and ~7–15 days for the fatigue component) reasonably predicted performance variation in the individual time series of the athletes studied — but to be genuinely precise it needs those constants CALIBRATED with each person's real performance data. Horme uses the typical population constants (42/7, the same practical convention used by endurance training-load tools), so the result is an INDICATIVE TREND, not a prediction calibrated to you.
Limitations: It was validated on short time series from a small number of athletes; the relationship between 'training impulse' and real performance is more complex and non-linear in practice; Horme has no objective performance data (times, marks) with which to calibrate the constants individually.
A means of assessing maximal oxygen intake: correlation between field and treadmill testing
Cooper KH · 1968 · JAMA
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Supports: The distance covered running in 12 minutes allows VO₂max to be estimated without a laboratory
Effect: The distance in 12 minutes correlated strongly with treadmill-measured VO2max in adult men, yielding the most widely used field equation in the world (VO2max ≈ (meters − 504.9) / 44.73).
Limitations: Validated in young, trained military men, so extrapolation to other populations adds error (typically ±3.5 ml/kg/min or more). Requires a MAXIMAL effort and well-paced rhythm: starting too fast produces a lower result than actual capacity, and the equation cannot distinguish that from low fitness. Horme cautions on both and returns the result with its error band, never a bare number.
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