Thermodynamic entropy management in human motor control across circadian and thermal challenges

The second law of thermodynamics dictates that local decreases in entropy must be offset by increases elsewhere. While this principle is well established in mechanical systems, its role in biological motor control remains underexplored. This study analysed 576 bimanual coordination trials on 16 participants collected across circadian cycles under normal conditions and thermal perturbations to test whether human motor systems strategically regulate functional movement stability. Movement entropy peaked during circadian temperature minima at dawn and declined to its lowest level during temperature maxima in the late afternoon, showing a significant inverse correlation with core body temperature. Thermal perturbations using heat and ice vests amplified these circadian patterns, with cold challenges exerting stronger effects than heat challenges. Despite substantial variations in movement entropy across conditions, task performance in maintaining target phase coordination remained stable. These findings provide preliminary evidence that biological systems can achieve local order through strategic entropy redistribution, increasing movement variability under challenging physiological conditions. The results offer initial empirical support suggesting that human motor control can function as an entropy-management system, revealing how biological systems satisfy thermodynamic laws while preserving functional stability.