• Cardiac function emerges as an integrated system linking heartbeat mechanism, myocardial energy regulation, and autonomic control, with concurrent measurements of cardiac output, postural effects, and reflex regulation across studies of heart beat mechanics, energy regulation, and neural control [1], [4], [6], [10], [17], [18].

• Skeletal muscle energetics center on phosphagen metabolism, phosphate diffusion, and electrolyte balance, connecting substrate availability to contraction power and external work in both humans and animals [2], [9], [12], [15], [16], [20].

• Mechanical properties and contraction dynamics emphasize viscoelastic behavior, contraction duration and muscle contractures as determinants of performance and fatigue, revealing mechanical limits of muscle function [2], [9], [13], [14], [20].

• General physiology frameworks and cross-system methodologies provide overarching measurement principles and cross-tissue comparisons that unify circulatory, muscular, and neural physiology across species [3], [7], [8], [19].

• Ionic regulation and excitability in muscle and heart are treated as core determinants of fatigue, signaling, and contraction, with hydrogen ion concentration, potassium balance, and phosphate transport guiding metabolic and electrical responses [5], [6], [12], [16].