On vigorous exercise, the respiratory function largely depends upon -

During intense, intermittent exercise and throughout prolonged physical activity, muscle glycogen paicles are broken down, freeing glucose molecules that muscle cells then oxidize through anaerobic and aerobic processes to produce the adenosine triphosphate (ATP) molecules required for muscle contraction.The rate at which muscle glycogen is degraded depends primarily upon the intensity of physical activity; the greater the exercise intensity, the greater the rate at which muscle glycogen is degraded. As a result, high-intensity activity, such as repeated sprinting, can quickly lower glycogen stores in active muscle cells, even though the total time of activity might be relatively brief (eg, 10 x 30-s sprints with sho recovery intervals). In comparison, an endurance athlete who trains for hours at a time will also experience a marked decline in muscle glycogen, although at a slower rate of degradation than the sprinter. Ref Davidson 23rd edition pg 730