SYNTH-23 · Guide
PMEP-5 Muscle Damage/Trauma Model
Decision framework
When this model is the limiter
The muscle damage model is not a meaningful limiter in efforts under ~1-2 h — there, the cardiovascular-anaerobic and neuromuscular models (REF-459) explain fatigue better (the base's reading of the REF-459 framework, not a measured cut-off). It becomes relevant when the event combines long duration with repeated high-force efforts, i.e.:
1
Durability — holding power late in a long road/gravel race: fresh VO2max and FTP did not predict how much amateurs faded (−10% in 5-min and 20-min power after 1000 kJ at 80% of 20-min power, REF-427; no damage marker was measured there — that muscle damage drives the fade is inference).
2
Multi-day / stage racing and dense blocks — after unaccustomed eccentric arm work in untrained men, voluntary and evoked strength stayed depressed for 72-96 h while the concentric arm recovered within 24 h (REF-702); fuel stores are assumed to refill faster than that (not from a study). *Inference:* contractile recovery, not glycogen, is what constrains back-to-back quality days after a damaging one.
3
Terrain with an eccentric component — trail/mountain running, long descents, off-road repeated impacts (REF-549, REF-660). *Inference* (no damage marker was measured): the uphill-and-steady part of a trail effort is probably not where the damage shows — in 23 trained trail runners, 3 h on a treadmill with a +12% uphill time trial every hour cost 6.6% of uphill TT distance while oxygen cost, energy cost and leg stiffness were preserved (REF-548; no descents in the protocol).
Discipline ranking of exposure (base inference; only runners vs cyclists is measured, the order within running and within cycling is not): trail/downhill running > road running > mountain biking > road cycling.
The measured anchor is REF-235: after 3 days of 2.5 h at 70% VO2max, runners showed 133% higher CK, 404% higher myoglobin, 87% higher CRP and 256% higher IL-6 than cyclists, while innate immune measures and 12-week URTI symptoms did not differ — *inference, not tested* (one 3-day block, not progressive volumes): an argument for cycling as the cross-training modality in high-frequency blocks.
Damage in cycling is still real: CK and myoglobin rose after real U23 races (REF-703).
What raises damage
Force per contraction, not average power. Damage tracks mechanical strain — non-uniform sarcomere lengthening, "popping" of the weakest sarcomeres — rather than metabolic cost (REF-704 mechanism). *Inference from that:* big-gear/low-cadence work and long climbs at low RPM raise peak crank torque and therefore peak fibre force; no cited study measured damage by cadence.
Duration × repetition — hours of repeated contractions accumulate structural cost even at moderate force (inference); what was measured is that markers rose after both a road race and an MTB race (REF-703).
Eccentric exposure — descents, plyometrics, heavy lowering work; after an identical arm-curl bout the eccentric arm had 82% disrupted fibres against 33% for the concentric arm in untrained men (REF-702).
Levers — what to actually do
1. Build damage resistance (weeks-months; the base's judgement is that this is the highest-value lever)
Heavy gym strength, 2×/week, is the route to late-race power with a trial behind it (one, REF-146): it raised 5-min power after 185 min of cycling from 371 to 400 W in well-trained cyclists (REF-146, B+, 20 riders) and raised isometric strength and 30-s Wingate power in elite cyclists over 10 weeks, with a threshold-power tendency and a non-significant 40-min result (REF-147, B+, 20 riders).Neither trial measured muscle damage; the muscle-damage model supplies a *mechanism* — trained muscle disrupts less under the same load (REF-702) and, as one proposed mechanism, adds sarcomeres in series after a damaging bout (REF-704).
High-torque / low-cadence cycling efforts are the on-bike analogue. Mechanistically plausible, not directly tested for damage resistance — hold this as a hypothesis, not a proven protocol, and note that SYNTH-17 advises against imposed low-cadence work at moderate intensity (no efficiency or performance gain, REF-118).
Sport-specific eccentric exposure where the event demands it: prior exposure to downhill running is the best-supported preventive strategy (REF-660); a single eccentric bout protects against damage from later bouts (REF-549, review). The "1-3 weeks out" timing is the base's practice — REF-704 describes much less damage from a second bout a week after the first.
2. Reduce damage during the event
Fuel high. 120 g CHO/h during a mountain marathon produced lower CK, LDH and GOT 24 h post-race and lower internal load than 60 or 90 g/h in 20 gut-trained elite male runners, roughly 7 per arm, one race (REF-331, B+). Transfer to amateurs and to cycling is untested, and 120 g/h is only usable when gut-trained and tolerated. Mechanism unclear; the effect is one more argument for the high-carb race protocol already used for the energy-stores model.
Cadence/gear management on long climbs — the energetically optimal cadence fell after 55 min of cycling in 14 experienced cyclists, read as more type I fibre contribution (REF-261); *inference:* spinning shifts load away from peak torque at some efficiency cost, whether that trade-off is worth it is untested — no study tested cadence against damage markers, and REF-261's own practical reading points the other way (let cadence fall late in a long ride; forcing the early cadence costs energy).
3. Recover after it
Contractile function after unaccustomed eccentric work was still depressed at 72-96 h in untrained men (REF-702; that this is longer than refuelling takes is the base's inference); in trained men the same bout produced less disruption (REF-702) — this, not glycogen, is what constrains back-to-back quality days (inference).
Modalities with evidence: cold-water immersion reduced CK (g −0.24) and soreness (g −0.40) across 30 RCTs, with no benefit to strength (MVIC) or jump recovery and an immediate inhibition of explosive power after partial immersion (g −0.94); leg-only and whole-body immersion were equivalent (REF-250).Compression garments moderately improved DOMS, strength, power and CK at 24-72 h across 12 studies (Hedges' g 0.40-0.49, REF-387); the "worn continuously 12-24 h" detail is the base's practice.Protein after the session gave the largest muscle-mass gain and protein at night the largest strength gain in resistance-training adults (REF-154, network meta-analysis); it did not measure recovery from damage, so its use for repair here is inference.
Masters athletes: the review of masters recovery kinetics concludes the age effect is smaller than originally suggested and largely explained by training status, with only limited evidence of slower recovery — but the same review reports reduced recovery of neuromuscular function in masters after muscle-damaging exercise (a 55-km trail run, a 10 × 10 leg-press bout) and concludes recovery is not affected by age unless muscle damage delays it (REF-598).Spacing hard eccentric sessions 48-72 h apart in older athletes is the base's own practice, not a finding — the review reports no interval.
Scheduling rules (base practice built on [REF-701], meta-analysis)
Never test in the 24-48 h damage window (the window is base practice; the abstract gives 24-48 h only for the VO2 outcome) — after a damaging protocol sprint and incremental peak power were significantly reduced while time-trial and distance-trial output were not (REF-701), so a ramp test or sprint profile taken there under-reads the athlete asymmetrically.
Steady endurance/tempo in that window is fine (base practice), but expect elevated RPE and ventilation at unchanged oxygen consumption — this dissociation is the meta-analytic finding (REF-701); *inference:* by itself it is not evidence of overreaching.
Put the damaging session after the testing/sprint session, not before, when both are in the same microcycle (base practice following from the above).
What NOT to do
Do not treat a CK or myoglobin number as a durability score. In REF-703 post-race CK rose only in road cyclists and myoglobin only in mountain bikers, and the association with the time gap to the winner ran in opposite directions (smaller gaps with lower ΔMB on the road, with higher ΔCK off-road); no single marker is accepted even for diagnosing overtraining (the ECSS/ACSM consensus: of the hormonal, biochemical and immune markers in use, none meets all criteria for general acceptance, REF-206 — a statement about overtraining diagnosis, applied here by inference).
Do not use soreness as the readiness gate — soreness develops the day after (REF-704); *inference from that review's model, not measured there:* it lags the force loss and length-tension shift that mark the damage.
Do not blanket-suppress the inflammatory response with routine high-dose NSAIDs/antioxidants around training aiming to "reduce damage"; adaptation depends on the signal (REF-457 on adaptation signalling; base inference for the practical rule).
Open questions
Does high-torque/low-cadence cycling actually confer damage resistance? Mechanistically plausible, untested directly.
Is there a dose of eccentric exposure that improves cycling durability without costing quality elsewhere?
The trained-vs-untrained protection data come from arm-curl studies with 6 and 8 men, compared across two separate papers (REF-702) — the leg/endurance equivalent is not established.
How this entry was checked and changed
Content correction 2026-09-27
"Masters recover contractile function more slowly — space hard/eccentric sessions 48-72 h (REF-598)" -> REF-598's corrected entry: the age effect is smaller than originally suggested and largely explained by training status, with limited evidence on recovery kinetics and no interval; the 48-72 h spacing is labelled base practice.
"The eccentric phase is several-fold more damaging" -> stated with the abstract's figures (82% vs 33% disrupted fibres untrained; 45% eccentric in trained, concentric not different from baseline).
"Leg-only CWI is sufficient (REF-250)" -> abstract: CK and DOMS improved, no MVIC or CMJ recovery benefit, immediate CMJ inhibition after partial immersion (g −0.94), partial = whole-body; "compression 12-24 h post" -> the meta-analysis measured 24-72 h (g 0.40-0.49, 12 studies); the wear duration is base practice.
REF-147 "performance measures" -> strength and 30-s Wingate up, 4 mmol/L tendency, 40-min not significant; REF-427 restated with its protocol and −10% declines; REF-235, REF-703, REF-701, REF-261, REF-331 restated with abstract figures; cadence-torque and 1-3-week eccentric timing labelled inference/base practice.
(sync 2026-09-27, after the full-base pass) REF-548 cited for eccentric/descent damage in trail -> its corrected entry is a treadmill protocol with uphill TTs and no descents that found "high durability" (−6.6% uphill TT distance, energy cost and leg stiffness preserved); citation moved to a sentence stating that.
REF-704 "adds sarcomeres in series" and "soreness does not track the force loss" -> the review gives sarcomere addition as one proposed mechanism and only says soreness appears the day after; the lag is now labelled inference.
REF-154 "protein intake supports repair" -> the NMA measured muscle mass/strength gains with timing (post-exercise for mass, night for strength), not damage recovery; restated, repair labelled inference.
REF-459 "six-model PMEP framework" -> the corrected entry lists eight linear models plus a complex-systems integration.
Durability claims re-checked against the corrected entries: REF-196 (Valenzuela 2022b) lost 2.9% on average with no relation to lab indicators and did not analyse fat oxidation in its abstract; REF-423 (Passfield & Doust 2000) ran no predictor analysis; REF-424 (Spragg) found the rested profile, VO2max included, positively related to durability. Statements attributing "fat oxidation r=+0.61", "−8.7%", or "VO2max did not predict" to these papers were corrected.
Resync 2026-09-28: re-read against REF-598, REF-366 and REF-423 after their full-text/PMID corrections today; no claim here depends on what changed.
Verification 2026-10-01: every quoted figure checks against the snapshot — REF-235 (133/404/87/256%), REF-702 (82/33/45%), REF-146 (371→400 W, B+, n=20), REF-147, REF-250 (g −0.24/−0.40/−0.94, 30 RCTs), REF-387 (g 0.40-0.49, 12 studies), REF-331, REF-548 (6.6%), REF-427, REF-703, REF-701. One number is misread (72-96 h is 'still depressed', not a recovery time).
Verification 2026-10-01: the framework is candid that its central mechanism is inferred (strength trials measured no damage; mechanism from arm-curl biopsies; high-torque work a hypothesis). The real problems are the cadence lever, whose cited entry advises the opposite, REF-207 cited for something it does not say, and the REF-598 sentence dropping the muscle-damage exception.
Verification 2026-10-01: entry has no Tier / Applicability line (older layout); sources span Tier 1 untrained arms to Tier 4-5 elite runners with transfer stated only in Open questions.
Verification 2026-10-01: REF-196, REF-369, REF-423, REF-424 appear only in the correction log and were not audited. All cited entries have a DOI; no SOURCE flags.