ABSTRACT
The physiological response to exercise involves primarily cardio-respiratory and metabolic adaptations. The exact physiological response is determined not only by the intensity and duration of exercise but also by the underlying level of fitness of the individual. Muscle blood flow is increased during exercise as a consequence of accumulation of metabolites such as adenosine and potassium. Consequently, SVR is reduced. Oxygen extraction by the muscle is also increased during exercise. As glycogen stores become depleted during prolonged exercise, the metabolic substrate switches to fatty acids. If fat is fully oxidised via the Krebs cycle it leads to the generation of 129 molecules of Adenosine triphosphate (ATP). The rate of ATP re-synthesis from fat is too slow to be of great importance during high-intensity exercise such as sprinting however it is important during endurance exercise. However, in extreme conditions protein can be used to generate ATP.
