What happens to the body when physical activity increases?

When physical activity increases, the body experiences several physiological changes aimed at meeting the heightened demands for energy and oxygen. The correct answer highlights two important adaptations: an increase in energy production (in the form of ATP) and an increase in breathing rate.

During exercise, the muscles require more ATP to sustain higher levels of activity. The body responds by mobilizing energy stores and enhancing the processes of aerobic and anaerobic metabolism to generate ATP. Additionally, the demand for oxygen rises as the muscles work harder, which drives an increase in the breathing rate. This ensures that the body can supply enough oxygen to the bloodstream and, consequently, to the muscles.

These adaptations allow the body to maintain performance and endurance during physical activity. By increasing energy production and oxygen intake, the body effectively supports its increased physical demands, leading to improved exercise capacity and better overall fitness.