Peripheral factors as limitations to exercise capacity.

The paper focuses on two aspects of the peripheral limitations to exercise: (a) intracellular and extracellular substrates used for energy transduction and (b) the metabolic potential of muscle. The major substrates used to support contractile activity have been discussed in reference to high-intensity, short-term exercise and moderately-intense, long-term exercise. It has been suggested that substrate availability is a prime candidate as a limiting factor to prolonged exercise, whereas, it is clearly not a limiting factor in short-term maximal efforts. Consideration of the metabolic potential of muscle as a possible limiting factor to exercise has been divided into anaerobic metabolism, aerobic metabolism and regulatory factors. It appears that the enzymatic capacity of the energy transducing pathways is not a limiting factor to any type of exercise.