What is meant by breathing? What happens to the rate of breathing during vigorous exercise and why?

(N/A) $1$. Breathing is the physical process of inhaling oxygen-rich air and exhaling carbon dioxide-rich air.
$2$. During vigorous exercise, the rate of breathing increases significantly.
$3$. This happens because the body requires more energy for muscular activity, which can only be released through increased cellular respiration.
$4$. Increased breathing ensures a higher supply of oxygen to the cells to meet this energy demand.
$5$. If oxygen supply is insufficient, muscles respire anaerobically, producing lactic acid, which leads to muscle fatigue.