Effect of Activity on Respiration

Cellular respiration is a set of metabolic reactions and processes that take place within the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP). This is then released to fuel other cellular processes.
The increased demand for energy during physical activity causes the rate of this respiration process to accelerate.
This is because your body’s muscle tissues require more energy to contract and relax during exercise. The energy is obtained from the breakdown of glucose during respiration.

Under normal conditions, muscles perform aerobic respiration which requires oxygen and glucose, releasing carbon dioxide, water and large amounts of ATP.
During intense physical activity when the oxygen supply cannot meet the muscular demand, cells switch from aerobic respiration to anaerobic respiration.
In anaerobic respiration, glucose is converted into lactic acid and a smaller amount of ATP. This allows muscles to continue to work when there is insufficient oxygen.
Anaerobic respiration often leads to muscle fatigue due to the accumulation of lactic acid.

Following exercise, the body enters a recovery period during which the lactic acid produced through anaerobic respiration is removed from the muscles and converted back into glucose in the liver.
This process, known as the Cori cycle, requires oxygen and is the reason for continued heavy breathing even after exercise has ceased.
This extra oxygen consumed during the recovery period, referred to as the oxygen debt, compensates for the previously insufficient oxygen supply and helps restore the body’s energy reserves.

Regular exercise leads to physiological adaptations, including improved efficiency in respiration and energy use.
With consistent training, muscles develop more mitochondria (the site of aerobic respiration), improving the capacity and efficiency for aerobic respiration, hence one can exercise for longer periods before fatigue sets in. This enhanced ability is part of improved muscular endurance.
The cardiovascular system also benefits from consistent exercise. There is an increase in heart size, strength, and cardiac output, improving the body’s ability to distribute oxygen to the muscles efficiently.