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.

25+
Aerobic physiology
35+
Concurrent training
40+
Motor learning
25+ 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)
35+ 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
40+ 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.