Endurance time as a function of work in terms of fraction of maximal aerobic capacity is suggested on the basis of the current literature on physiological responses to work. The third of the endurance time to exhaustion is used as a safe working period. The recovery time or rest period for each working time is scheduled on the basis of the data in the literature on lactic acid production in the muscles, its diffusion into and its rate of elimination from the circulatory system.
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