Hypertrophy Simulation

Simulates muscle hypertrophy based on the stimulating reps model rather than volume load (sets × reps × weight). Key factors: CNS fatigue, calcium ion accumulation, and inflammation.

Constants

• +atrophy-onset-days+ (2.0) - how long before catabolism kicks in after stopping training
• +repair-capacity-per-day+ (2.0) - max structural damage repair rate
• +fascicle-decay-rate+ (2.0) - sarcomeres lost faster than myofibrils during detraining
• +inflammation-threshold+ (6.0) - damage level that triggers inflammation (shunts MPS to repair)
• +light-load-mur-ceiling+ (0.85) - 16-30RM loads can't fully recruit motor units
• +very-light-load-mur-ceiling+ (0.70) - 30RM+ even worse
• +fast-twitch-atrophy-multiplier+ (1.6) - type II fibers atrophy faster (not used daily)
• +early-training-sarco-bonus+ (2.5) - fascicle length gains dominate in first ~4 weeks
• +sleep-deprivation-cns-penalty+ (0.25) - sleep loss reduces MUR by 25%
• +short-rest-threshold-seconds+ (90) - shorter rests = MPS and CNS penalties

State

Systemic state tracks:

• supraspinal-fatigue (0-1) - global fatigue affecting all motor units
• crossover-fatigue-pool - fatigue from training one limb spilling over
• responder-type - high/average/low affects damage susceptibility

Muscle state tracks per muscle:

• myofibrillar-mass - CSA
• fascicle-length - sarcomeres in series
• calcium-ion-fatigue - peripheral fatigue
• structural-damage - accumulated damage
• accumulated-stimulus-quality - quality of hypertrophic stimulus
• hours-in-mps-window - duration of elevated MPS

Core logic

Set effectiveness

Steep diminishing returns:

• Set 1: 100%
• Set 2: 35%
• Set 3: 20%
• Set 4+: ≤15%

First set generates most of the stimulus. Later sets add damage without proportional stimulus.

Motor unit recruitment

Base MUR from RIR and exercise stability, capped by load type. Light loads can't reach full recruitment. Sleep deprivation further reduces ceiling.

Tension

tension = local_penalty × cns_penalty × recovery_penalty

CNS penalty is non-linear - small fatigue causes disproportionate drops.

Damage

Damage keeps accumulating even when stimulus drops off: damage = base × stretch_mult × rir_mult × individual_mult

This is the "junk volume" problem.

Adaptation

CNS recovery

Exponential decay, ~6h half-life. Two-a-days with 8h gap should work; 1h gap will tank performance.

Hypertrophy

Occurs during MPS window (24-48h). If inflamed, MPS goes to repair instead. Early training favors fascicle length over CSA.

Atrophy

Starts after 2+ days without stimulus. Exponential decay toward baseline. Type II fibers and fascicle length atrophy faster.

Collagen

Severe chronic damage deposits collagen that impairs strength-to-mass ratio and doesn't fully clear.

Special cases

Aerobic interference - causes damage and elevates MPS, but MPS goes entirely to repair. Atrophy clock keeps running.

Short rests (<90s) - reduce MPS response by 30%, CNS doesn't clear between sets.

Drop sets - severe CNS fatigue, light loads at end cause even more fatigue.

Sleep deprivation - reduces MUR ceiling 25%, recovery takes 40% longer.

Muscle memory - peak mass is tracked. If current < peak, regaining is faster due to retained MUR ability.

Tests

test.lisp has scenarios like:

• 3×3/week vs 9×1/week (frequency vs volume)
• 20 sets/day (junk volume causing inflammation)
• detraining (exponential loss, faster fascicle decay)
• two-a-days with different rest gaps
• individual responder variation