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Evidence

The primary sources
Terav is built on.

Every rule the engine applies traces to one of these. Where the literature isn’t there — session length, exact retest cadence, specific cue phrasing — we tag the choice as engineering in the app, not science.

28
Aerobic physiology
23
Concurrent training
37
Motor learning
28 primary sources

Aerobic physiology

The base for Engine Builder. What actually adapts in the first 8 weeks of aerobic work, at what dose, and which metric to track.

  • Little JP et al. 2010, J Physiol 588(6):1011-1022
    HIIT drives PGC-1α +25% and mitochondrial protein content in 2 weeks (n=7)
  • Perry CG et al. 2010, Appl Physiol Nutr Metab 35(6):837-844
    7 weeks 3×/wk HIIT: citrate synthase / β-HAD / COXIV +28-36%
  • Konopka AR et al. 2014, J Gerontol A 69(4):371-378
    12 wks progressive cycling: PGC-1α +55-62%, CS +65-102%, COXIV +80-126%; no age difference
  • Bishop DJ et al. 2019, Physiology 34(1):56-70
    Molecular pathway synthesis for mitochondrial biogenesis (AMPK, Ca²⁺/CaMKII, p38 MAPK)
  • Egan B, Zierath JR 2013, Cell Metab 17(2):162-184
    Molecular exercise-adaptation review — the definitive reference for the pathway map
  • Andersen P, Henriksson J 1977, J Physiol 270(3):677-690
    Foundational: capillary density +20%, VO2max +16% in 8 weeks of endurance training
  • Cocks M et al. 2013, J Physiol 591(3):641-656
    SIT and MICT both produce comparable capillary-to-fibre ratio + eNOS gains
  • Helgerud J et al. 2007, MSSE 39(4):665-671
    Norwegian 4×4: stroke volume +10% only in the interval group; the canonical intensity anchor
  • Wisløff U et al. 2007, Circulation 115(24):3086-3094
    12 wks 4×4 in post-MI heart failure: VO2peak +46%, LV EF +35%
  • Baggish AL, Wood MJ 2011, Circulation 123(23):2723-2735
    Endurance drives eccentric LV hypertrophy; strength drives concentric
  • Brooks GA 2018, Cell Metab 27(4):757-785
    Lactate shuttle theory synthesis — the update on Z2 substrate physiology
  • San-Millán I, Brooks GA 2018, Sports Med 48(2):467-479
    Metabolic flexibility, Zone 2 lactate clamp — practical basis for Z2 pacing
  • Achten J et al. 2002, MSSE 34(1):92-97
    Fatmax at ~64% VO2max / ~74% HRmax — Z2 anchor
  • Tanaka H et al. 2001, JACC 37(1):153-156
    HRmax = 208 − 0.7 × age, SEE ~10 bpm
  • Nes BM et al. 2013, SJMSS 23(6):697-704
    HUNT: HRmax = 211 − 0.64 × age — the modern replacement
  • Karvonen MJ et al. 1957, Ann Med Exp Biol Fenn 35(3):307-315
    %HRR (heart rate reserve) — foundational for zone determination
  • Bouchard C et al. 1999 HERITAGE, JAP 87(3):1003-1008
    Individual heritability of VO2max response 47%; ~10× range in individual gains
  • Bouchard C et al. 2011, JAP 110(5):1160-1170
    21-SNP model explains 49% of VO2max response variance
  • Joyner MJ, Coyle EF 2008, J Physiol 586(1):35-44
    VO2max plateaus but threshold + running economy keep improving — track threshold, not VO2max
  • Coyle EF et al. 1984, JAP 57(6):1857-1864
    Detraining: VO2max −7% at 12 days, −16% at 12 weeks
  • Mujika I, Padilla S 2000, Sports Med 30(2):79-87
    Detraining Part I; short-term losses
  • Mujika I, Padilla S 2000, Sports Med 30(3):145-154
    Detraining Part II; intensity > volume for maintenance
  • Ross R et al. 2015, Mayo Clin Proc 90(11):1506-1514
    Non-response at 50% intensity drops to 0% at 75% — often dose, not genotype
  • Hecksteden A et al. 2015, BJSM 49(23):1520-1526
    ≥2 baselines required to classify non-responder
  • Trappe S et al. 2013, JAP 114(1):3-10
    Octogenarian lifelong endurance athletes: VO2max ~38 mL/kg/min (~2× age-matched sedentary)
  • McNulty KL et al. 2020, Sports Med 50(10):1813-1827
    Menstrual cycle effect on performance: SMD ~0.06 (trivial average)
  • Seiler S 2010, IJSPP 5(3):276-291
    Polarised distribution — the 80/20 easy-vs-hard split behind the app's aerobic prescription
  • Bosquet L et al. 2007, MSSE 39(8):1358-1365
    Taper meta-analysis: −41-60% volume with intensity held adds ~3% to peak performance; the source for the app's taper protocol
23 primary sources

Concurrent training

How strength and aerobic work coexist without interference — session order, modality, dose, protein floor. What we ban PR-chasing during an aerobic block.

  • Hickson RC 1980, Eur J Appl Physiol 45:255-263
    The original 10-week concurrent study; strength plateaued at week 7 (design flaws acknowledged)
  • Atherton PJ et al. 2005, FASEB J 19:786-788
    AMPK-PKB molecular switch mechanism for the interference effect
  • Coffey VG, Hawley JA 2007, Sports Med 37:737-763
    Foundational integrative review of concurrent adaptation
  • Baar K 2014, Sports Med 44(S2):S117-S125
    3-hour AMPK window post-endurance; mTORC1 sensitised 18-24 h post-lifting
  • Fyfe JJ, Bishop DJ, Stepto NK 2014, Sports Med 44:743-762
    Definitive review of interference mechanism and its modulators
  • Wilson JM et al. 2012, JSCR 26:2293-2307
    21 studies, 422 ES: concurrent reduced strength ES ~18%, hypertrophy ~31%, power ~40%; running > cycling for interference
  • Murach KA, Bagley JR 2016, Sports Med 46:1029-1039
    Contrary evidence: hypertrophy not consistently reduced in ecologically valid protocols
  • Schumann M et al. 2022, Sports Med 52:601-612
    Modern reconciliation: max strength SMD −0.06 (n.s.); hypertrophy SMD −0.01 (n.s.); explosive strength SMD −0.28 (p=0.007)
  • Eddens L et al. 2018, Sports Med 48:177-188
    Resistance-before-endurance produced +6.91% lower-body dynamic strength gain vs endurance-first
  • Robineau J et al. 2016, JSCR 30:672-683
    ≥6 h separation preserves strength; 24 h optimises VO2max — the dose-response the app applies
  • Doma K et al. 2019, Sports Med 49:669-682
    Bidirectional damage: running-induced damage impairs subsequent squat/deadlift force for 24-48 h
  • Berryman N et al. 2018, IJSPP 13:57-64
    Cycling shows cleanest bidirectional compatibility with strength
  • Fyfe JJ et al. 2016, Front Physiol 7:487
    HIT+RT and MICT+RT produced same strength decrement — endurance INTENSITY does not mediate interference, VOLUME does
  • Petré H et al. 2018, JSSM 17:167-173
    Highly trained lifters: HIIT vs continuous produced same squat gains
  • Aragon AA, Schoenfeld BJ 2013, JISSN 10:5
    “Anabolic window” is 4-6 h, not 30 min
  • Morton RW et al. 2018, BJSM 52:376-384
    Meta-analysis: no further hypertrophy benefit above 1.62 g/kg/day protein
  • Jäger R et al. 2017, JISSN 14:20
    ISSN position stand: 1.4-2.0 g/kg/day for exercising individuals
  • Bartlett JD et al. 2015, Eur J Sport Sci 15:3-12
    “Train low, compete high” — low-CHO amplifies AMPK/PGC-1α/p53
  • Impey SG et al. 2018, Sports Med 48:1031-1048
    “Fuel for the Work Required” framework — the app's carb-around-session guidance
  • Butcher SJ et al. 2015, Open Access J Sports Med 6:241-247
    CrossFit Total is strongest predictor of Fran/Grace times
  • Meyer J et al. 2017, Workplace Health Saf 65:612-618
    CrossFit systematic review: VO2max, body comp, strength all improve concurrently in ~10 wk protocols
  • Feito Y et al. 2018, Sports 6:76
    16 weeks HIFT: strength AND VO2max improved concurrently
  • Brandt K et al. 2025, Front Physiol 16:1519240
    First HYROX physiological profiling: VO2max is strongest performance predictor
37 primary sources

Motor learning + skill acquisition

The base for skill programs — handstand, HSPU, muscle-up. Multi-dimensional generation, external-focus cues, contextual interference, spacing.

  • Fitts PM, Posner MI 1967
    Cognitive → associative → autonomous stages (descriptive framework)
  • Bernstein NA 1967, The Co-ordination and Regulation of Movements
    Mastery of redundant degrees of freedom; freeze → release → exploit
  • Newell KM 1985
    Constraints-led framework: organismic, task, environmental constraints
  • Karni A et al. 1998, PNAS 95:861-868
    Fast (within-session) vs slow (across-session) learning; M1 remapping over ~3 weeks
  • Doyon J, Benali H 2005, Curr Opin Neurobiol 15:161-167
    Cortico-striatal vs cortico-cerebellar loop — the two skill-learning circuits
  • Krakauer JW et al. 2019, Compr Physiol 9:613-663
    Best modern synthesis: use-dependent + error-based + reinforcement + strategic learning simultaneously
  • Wolpert DM, Ghahramani Z 2000, Nat Neurosci 3(Suppl):1212-1217
    Forward + inverse internal models
  • Shea JB, Morgan RL 1979, JEP Human Learning 5:179-187
    Contextual interference — blocked better in acquisition, random better in retention
  • Brady F 2004, PMS 99:116-126
    Meta-analysis d=0.38 overall; d=0.57 lab, d=0.19 applied/sport
  • Wulf G, Shea CH 2002, Psychonom Bull Rev 9:185-211
    Complex-skill principles differ from simple lab; reduce challenge early, add later
  • Zeng X et al. 2024, Sci Rep 14
    Modern meta confirming moderate CI benefit for retention
  • Henry FM 1968
    Specificity hypothesis; motor abilities are task-specific
  • Proteau L et al. 1992, QJEP 44A:557-575
    Learning specific to sensory conditions of practice
  • Kerwin DG, Trewartha G 2001, MSSE 33:1182-1188
    Handstand hold characterised as wrist-torque-dominated
  • Schmidt RA 1975, Psychol Rev 82:225-260
    Schema theory — variability builds recall and recognition schemas
  • Wulf G, Höß M, Prinz W 1998, JMB 30:169-179
    External focus outperforms internal (stabilometer, ski-simulator)
  • Wulf G 2013, Int Rev Sport Ex Psychol 6:77-104
    15-year review: external focus reliably better across ~100 studies
  • McNevin NH et al. 2003, Psychol Res 67:22-29
    Farther external targets → larger effect
  • Wulf G, Lewthwaite R 2016, PBR 23:1382-1414
    OPTIMAL theory — external focus + enhanced expectancies + autonomy
  • Halperin I et al. 2019, Front Sports Act Living 1:7
    Weightlifting: external focus improves 1RM, force, velocity in most studies
  • Salmoni AW, Schmidt RA, Walter CB 1984, Psych Bull 95:355-386
    Guidance hypothesis: 100% KR hurts retention
  • Winstein CJ, Schmidt RA 1990, JEP LMC 16:677-691
    50% faded KR ≥ 100% during acquisition; better on retention
  • Kernodle MW, Carlton LG 1992, JMB 24:187-195
    For complex tasks: KP > KR
  • Chiviacowsky S, Wulf G 2002, RQES 73:408-415
    Self-controlled KR beats yoked schedules
  • Chiviacowsky S, Wulf G 2005, RQES 76:42-48
    Post-trial choices > pre-trial
  • Ericsson KA et al. 1993, Psych Rev 100:363-406
    Original deliberate practice paper (elite violinists ~10,000 h)
  • Macnamara BN, Hambrick DZ, Oswald FL 2014, Psych Sci 25:1608-1618
    Deliberate practice explains 26% variance in games, 18% sports — 10k-hour rule not defensible
  • Macnamara BN, Maitra M 2019, Royal Soc Open Sci 6:190327
    Direct replication of Ericsson 1993 failed to reproduce strong effect
  • Walker MP et al. 2002, Neuron 35:205-211
    Sleep-dependent motor consolidation, ~20% overnight gain
  • Robertson EM, Pascual-Leone A, Miall RC 2004, Nat Rev Neurosci 5:576-582
    4-6 h post-practice consolidation window vulnerable to similar-task interference
  • Shea CH et al. 2000, Human Mov Sci 19:737-760
    Spacing across days > massing within day
  • Sleeper MD et al. 2012, Int J Sports Phys Ther 7:124-138
    Gymnastics Functional Measurement Tool, test-retest r=0.99
  • Sands WA 2000, Sports Med 30:359-373
    Women's gymnastics injury prevention — skill-readiness assessment
  • Gabbett TJ 2016, BJSM 50:273-280
    Acute-to-chronic workload ratio predicts injury (general mechanism)
  • Ackerman PL 1988, JEP Gen 117:288-318
    Cognitive ability predicts early stage; psychomotor autonomous
  • Wu HG et al. 2014, Nat Neurosci 17:312-321
    3× variance in visuomotor rotation learning; correlates with baseline motor variability
  • Kelso JAS 1995, Dynamic Patterns
    Sub-skills stabilise on their own attractors
Sources we explicitly flag as anecdotal

We reference (but do not cite as evidence) certain coach literature that is not peer-reviewed: Alex Viada’s The Hybrid Athlete; Fergus Crawley and Nick Bare’s personal training practice; HYROX coach commentary; Vladimir Uzunov’s Four Stage Training Model; the FIG Age Group Development Program; USA Gymnastics J.O. Compulsory levels; Balyi’s LTAD framework; GymnasticBodies, Bar Brothers, Progressive Calisthenics. When these appear in the app they are labelled “coaching consensus,” never “evidence.”

Full source reports are versioned in the codebase at dev/whitepapers/ — living documents that update as new primary sources land.