Chapter 61: Environmental Physiology

The cardiovascular system responds to exercise by increasing cardiac output through elevated heart rate and stroke volume, driven by sympathetic nervous system activation. Simultaneously, the body redistributes blood flow away from visceral organs toward active skeletal muscles and skin, mediated by local metabolic factors and neural regulation. Pulmonary ventilation increases proportionally with exercise intensity to meet the elevated oxygen demand and carbon dioxide elimination. The chapter emphasizes VO₂ max as a fundamental measure of aerobic exercise capacity, determined by the integrated performance of cardiovascular delivery and mitochondrial oxidative capability. Thermoregulation during exercise involves increased sweating and enhanced skin blood flow to dissipate the substantial heat generated by muscular work. Long-term training induces adaptive changes including skeletal muscle hypertrophy, capillary angiogenesis, mitochondrial biogenesis, and enhanced lactate metabolism, all of which improve exercise tolerance and performance. The autonomic nervous system coordinates these responses through sympathetic activation that increases heart rate and contractility while parasympathetic tone decreases. The chapter concludes by connecting these physiological mechanisms to clinical conditions such as cardiovascular disease and chronic obstructive pulmonary disease, where impaired oxygen delivery or utilization limits exercise capacity. By integrating energy metabolism, hemodynamic adjustments, respiratory responses, and thermal balance, this chapter demonstrates how exercise represents a significant challenge to homeostasis that elicits beneficial long-term physiological adaptations.