Sex-related differences in ratings of perceived exertion and estimated time limit.

The purpose of the present investigation was i) to study the effect of sex on ratings of perceived exertion (RPE) and estimation of time limit (ETL) during runs to exhaustion at both absolute and relative physical and physiological reference criteria, ii) to propose some recommendations for exercise intensity prescription from both RPE and ETL according to sex. Eight male and eight female middle-distance endurance-trained runners performed two exercises until exhaustion on an outdoor track. The first test was a graded exercise to determine maximal aerobic velocity (vV.O2max), the velocity at the lactate threshold (vLT), and the velocity at delta 50 (vDelta50: the velocity halfway between vV.O2max and vLT). The second test was a constant all-out run at vDelta50 to determine the time to exhaustion at this intensity (tlim). The results of this study showed that the female runners perceived exercise as being harder, felt that they could endure less and had higher heart rate values than males for a given absolute velocity (km.h-1) whereas there were no difference between males and females for a given relative velocity (%vV.O2max). Moreover, the female runners perceived exercise as lighter and felt that they could endure more than the males for a given absolute time period (in s) whereas there was no difference between males and females for a given relative time period (%tlim). This result may be explained by the fact that the same exercise intensity or duration corresponded to higher %vV.O2max and lower %tlim for the females compared to the males. Consequently, physical trainers can prescribe the same perceived ratings for a given percentage of vV.O2max or tlim both in male and female athletes.