Muscular Responses During and Following Acute Physical Activity Under Heat Stress

Acute exercise provides a unique challenge to several regulatory systems. From a circulatory and metabolic perspective, exercise is associated with a rise in systemic blood flow, which allows for the adequate delivery of oxygen to the working musculature, as well as the dissipation of metabolically generated heat to the environment. Prolonged exercise or repeated contractions also lead to the development of fatigue, characterized by a reduction in the ability to generate force or power. This loss of strength has both peripheral and central mechanistic causes, which are influenced by increases in whole-body temperature. Hence, when exercise is performed in hot environmental conditions, the development of hyperthermia contributes to alter skeletal muscle performance. The aim of this chapter is to provide a brief overview of the circulatory and thermoregulatory responses associated with acute dynamic exercise, as well as the influence of heat stress on the development of skeletal muscle fatigue. Skeletal muscle damage will also be addressed to provide a wider perspective on what occurs within active muscles during and following acute exercise.