Perception of Effort during Constant Work to Self-Imposed Exhaustion
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA
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This study describes the pattern of change in effort sense and the value of this pattern in predicting work end point at relatively high work intensity 80 VO2 max. Patterns of change of various physiological functions were also observed. Two modes of work walking and running were compared to ascertain generalizability of results. Subjects were 26 healthy male volunteers. Time to exhaustion ET did not differ between walking and running. As work continued during both tasks, significant increases of VE, VEVO2, VECO2 and HR and a significant decrease of ETCO2 were observed while VO2 and R remained fairly constant. VO2 and VE during the run were about 5 greater than during the walk. Ratings of perceived exertion RPE from the Borg Scale were identical for both conditions, increasing in near linear fashion from a value of 12.9 at 25 of total work time to 18.9 at exhaustion. RPE obtained at 25 and 50 ET were extrapolated to time of exhaustion the point of intercept corresponded to RPE for maximal work. At exhaustion, Ss rated perception of respiratory exertion for the walk as less than that for the run perception of leg exertion was not different for the 2 conditions. Plasma lactate, epinephrine and norepinephrine concentrations following exercise did not differ between the 2 conditions. It is concluded that, with the exception of VO2 and some ventilatory parameters, walking and running at the same relative work intensity resulted in comparable perceptual and physiological responses. Psychophysical judgments made early during work were found to be reasonably accurate predictors of exhaustion time.
- Stress Physiology