When a runner starts a race, his breathing must respond by increasing its rate so that more oxygen enters the lungs. This allows more oxygen to be taken into the blood supply that flows past the lungs and this takes more oxygen to the muscles, which are working and contracting much more rapidly.
The runner not only breathes in and out more often, he also breathes in and out more deeply. The lungs can take in eight times more air during exercise than at rest to cope with this extra demand.
The runner's heart rate also increases during running. This enables oxygen and glucose to get to the active muscles more quickly so they do not tire. To aid this, the blood vessels that supply the muscles get wider to get as much blood there as possible.
The rate of cellular respiration in the muscle cell increases, producing more carbon dioxide. This is removed by the increased breathing rate. If the exercise goes into an anaerobic phase, lactic acid is produced, and this leads to oxygen debt which means that the runner has to breathe heavily to recover after the run, and he might have sore muscles the next day.
The runner not only breathes in and out more often, he also breathes in and out more deeply. The lungs can take in eight times more air during exercise than at rest to cope with this extra demand.
The runner's heart rate also increases during running. This enables oxygen and glucose to get to the active muscles more quickly so they do not tire. To aid this, the blood vessels that supply the muscles get wider to get as much blood there as possible.
The rate of cellular respiration in the muscle cell increases, producing more carbon dioxide. This is removed by the increased breathing rate. If the exercise goes into an anaerobic phase, lactic acid is produced, and this leads to oxygen debt which means that the runner has to breathe heavily to recover after the run, and he might have sore muscles the next day.