Negative (Eccentric) Work. I Effects of Repeated Exercise

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Abstract
The physiological responses to repeated negative (downhill) work have been studied on 3 healthy male subjects aged 26-41 years. The results show a remarkable decline in [Vdot]o2 for a given work load ([Wdot]) from 19-7 ml. Kg−1 min−1 on day 1 to 120 ml. kg−1 min−1on Day 5 at the 60th min of exercise, representing a change of ’ apparent ’ mechanical efficiency of —0-43. However [Vdot]E for given [Vdot]co2; or [Vdot]Tand [Qdot] jH and blood lactic acid for given [Vdot]o2; remained unchanged. This was also true of Tty and sweat rate for given metabolic heat production. Thus provided respiratory, circulatory, and temperature measurements are related to the appropriate physiological variable, valid comparison can be made between and within groups of subjects independently of the degree of habituation. This is marked contrast to the situation found for positive work (Davies et al. 1970). It was suggested that the decrease in the [Vdot]o2/[wdot] relationship was in part due to an increase in muscular strength and co-ordination resulting in the improved capacity of the subject to maintain body equilibrium and given stride length