ABSTRACT
Maximal exercise is defined here as exercise of an intensity that requires 100% of the maximal oxygen uptake (V̇O2 max). Exercise that has an oxygen requirement above an individual’s V̇O2 max (and that therefore is associated with an obligatory anaerobiosis to meet the energy demand) can thus be described as supramaximal, while exercise that requires an oxygen uptake below V̇O2 max can be termed submaximal. Maximal exercise can be sustained for only about 4-8 minutes before exhaustion occurs (Billat et al., 1994b). Therefore, most forms of recreational exercise, and indeed many sports, can be considered to be submaximal. Continuous submaximal exercise can also be termed
endurance exercise. The causes of fatigue during submaximal exercise are manifold and complex but may depend upon whether the exercise is of a sufficiently low intensity that adenosine triphosphate (ATP) resynthesis is almost completely aerobic or whether supplementary anaerobiosis is required, resulting in a progressive accumulation of blood lactate. For low-intensity submaximal exercise, fatigue may result from substrate depletion, dehydration, hyperthermia, or loss of motivation associated with central fatigue (Newsholme et al., 1992). For high-intensity submaximal exercise, fatigue may result from the effects of acidosis on muscle contractile function or on inhibition of key glycolytic enzymes (Edwards, 1981). Understanding the physiological limitations to submaximal exercise is important in developing training programmes to enhance endurance performance.
