The body adapts to an increase in physical activity through a series of physiological changes that improve efficiency and performance. Initially, during regular exercise, the heart will pump more blood, enhancing oxygen delivery to muscles. Over time, adaptations include increased muscle strength, improved endurance, and enhanced cardiovascular function, such as a lower resting heart rate. Additionally, mechanisms like improved mitochondrial density enable muscles to utilize energy more effectively. These adaptations contribute to overall improvements in physical fitness, allowing individuals to handle greater workloads and recover faster.