A Thermodynamic Theory of Neuromuscular Performance

Current exercise science lacks theoretical unity, treating training volume as mechanical work (repetitions load) while describing fatigue through separate physiological models.This fragmentation persists despite clear volume-fatigue relationships and evidence that mechanical calculations poorly predict training outcomes.We propose a thermodynamic framework that unifies these concepts by reconceptualising both as manifestations of the same process.Drawing on non-equilibrium thermodynamics, exercise represents the universal biological challenge of maintaining organisational integrity whilst dissipating energy.Our framework introduces "performance orders" to quantify organisational challenges under varying entropy conditions.Training volume therefore becomes the sum of organisational challenges rather than mechanical work, whilst fatigue reflects systemic entropy across multiple temporal scales.This explains why mechanically equivalent training produces different physiological responses, why subjective difficulty (RPE) predicts outcomes better than percentage-based programming, and why individuals show different recovery requirements despite identical performance capacities.We present conceptual mathematical models describing entropy dynamics during exercise enabling a systems-level approach that connects exercise science to broader biological principles.This suggests training programmes should focus on managing entropy generation rather than accumulating mechanical work, offering new approaches to individualised programme design.