The effects of voluntary contraction intensity and gender on perceived exertion during isokinetic quadriceps exercise.

The objectives of the present study were to: (1) examine perceived exertion across different target voluntary contraction intensities, (2) compare perceived exertion ratings with actual target intensities, and (3) compare perceived exertion ratings between males and females. The subjects for this study included 30 healthy, college-aged male (n = 15) and female (n = 15) volunteers. All subjects were free of orthopedic, cardiopulmonary, systemic and neurological disease. Each subject completed five maximal isokinetic, concentric quadriceps contractions in a seated position at 60 degrees.s-1 to determine their single, highest peak torque. All subjects then completed, in a random order, 3-5 submaximal isokinetic contractions at 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of their single, highest peak torque. Each relative contraction level (i.e., percentage) was achieved by having the subjects attempt to match the peak of their torque curve to a horizontal line on a computer monitor. Perceived exertion was measured by asking the subjects to provide a number that corresponded to the feelings in their quadriceps during exercise by viewing a modified category-ratio (CR-10) scale. The results of a two-factor (gender x intensity) analysis of variance revealed a significant, intensity main effect (F8,232 = 92.19, P < 0.001, eta 2 = 0.77, 1 - beta = 0.99) and no significant gender main effect (F8,232 = 2.66, P = 0.11, eta 2 = 0.09, 1 - beta = 0.35) or interactions (F8,232 = 1.01, P = 0.43, eta 2 = 0.04, 1 - beta = 0.46). The findings of this study demonstrate that perceived exertion is significantly (P < 0.05) different from the specific target values on the CR-10 scale at 10%, and 50-90% maximum voluntary contraction. The results revealed that the increase in perceived exertion across the contraction intensities could be fit to both linear (F1,29 = 205.41, P < 0.001, eta 2 = 0.88, 1 - beta = 0.99) and quadratic (F1,29 = 10.05, P = 0.004, eta 2 = 0.26, 1 - beta = 0.87) trends. These findings suggest that perceived exertion is underestimated during submaximal isokinetic exercise, and is not different between males and females.