The effects of rest interval on quadriceps torque and perceived exertion in healthy males

The ability to generate maximal muscular force is dependent upon time mediated mechanisms of fatigue. Interset rest interval length may not only affect force production but may also manifest changes in ratings of perceived exertion (RPE). The purpose of this study was to examine the effects of rest interval on quadriceps torque and RPE during multiple sets of resisted knee extensions.

14 healthy male volunteers were assessed for concentric isokinetic quadriceps peak torque, total work, and average power on the Biodex System II Isokinetic Dynamometer at a preset angular velocity of 180 deg.sec-1. Perceived exertion was measured with a modified category-ratio scale (CR-10). Under isometric conditions the perceptual range was anchored with one high and two low anchors. Subjects were randomly assigned to one of two groups: short rest interval (Group 1, 40 sec) and long rest interval (Group 2, 160 sec). All subjects performed 4 sets of 20 maximal isokinetic contractions with an inter-set rest interval that corresponded to their group assignment. Following the completion of each set subjects were asked to assign a rating out of 10 to the feelings in their quadriceps by visually observing a chart of the CR-10 scale.

The results demonstrated a significantly greater decline in quadriceps peak torque (p < 0.05), total work (p < 0.05), and average power (p < 0.05) by Group 1 as compared to Group 2. Changes in RPE across the 4 sets of exercise did not show a significant difference between the 2 groups.

The generation of quadriceps torque is a function of rest interval length, whereas perceived exertion appears to be unaffected.