Perceived exertion is elevated in old age during an isometric fatigue task

The purposes of this study were to compare the ratings of perceived exertion (RPE) of young [25 (1) years] and old men [84 (1) years] during intermittent (3 s on, 2 s off) voluntary isometric contractions of the elbow flexors at 60% of each subject's maximal voluntary contraction (MVC) force, and to determine whether potential differences in RPE were accompanied by altered neuromuscular parameters during fatigue. Subjects performed the fatigue protocol on two different visits. All subjects in both groups reported a maximal (10) perceived exertion using a modified Borg-scale at fatigue, but the old men reported a greater perceived exertion compared to the young men at an initial stage of the protocol during the two visits (P<0.05). The amount of prefatigue MVC force remaining at fatigue was not different between groups (~57%), and voluntary activation, as assessed with twitch interpolation, was not different from the prefatigue value for either group throughout the fatigue protocol (>95%), and did not show any age-related difference. Moreover, there was no significant difference in 60% target electromyography between groups at any time point during the fatigue protocol, and there was no significant effect of age on the decline in 50-Hz tetanic force. Thus, the old men were able to exert themselves to the same relative degree of muscle fatigue as the young men, and despite an elevated perceived exertion compared to the young men during initial stages of the protocol, they did not terminate the protocol prematurely, or demonstrate an inability to sustain a high level of voluntary activation.