Maximal exercise refers to physical activity performed at the highest intensity that an individual can sustain for a short period. In physiological anthropology, the study of physiological responses to maximal exercise is important for understanding human adaptation, physical performance, differences among populations, and the influence of age, sex, body composition, nutrition, and environment on exercise capacity. During maximal exercise, the body undergoes rapid and coordinated changes in the cardiovascular, respiratory, muscular, metabolic, and thermoregulatory systems. The cardiovascular system responds immediately to maximal exercise by increasing heart rate, stroke volume, and cardiac output. Heart rate rises progressively toward the individual's maximum, while cardiac output may increase several times above the resting level. Blood flow is redistributed mainly toward active skeletal muscles to meet their increased demand for oxygen and nutrients. Blood pressure, particularly systolic pressure, also increases. In trained individuals, the cardiovascular system generally works more efficiently, allowing greater oxygen delivery to working muscles.