Why does the breathing rate increase during exercise?

The breathing rate increases at the start of exercise then reaches a peak and plateaus during exercise. After exercise the breathing rate will gradually fall, but this may take several minutes.

During exercise our demand for energy INCREASES. The increase in breathing rate allows for MORE oxygen to enter the body. This oxygen is used for aerobic respiration to produce MORE energy.

Extension: Energy from respiration is generated in the form of ATP, the energy currency of a cell.