Perceived exertion responses to acute bouts of resistance exercise: EMG and blood lactate mediators

This study examined ratings of perceived exertion (RPE) during resistance exercise. In addition, changes in blood lactic acid and biceps muscle activity assessed using electromyography (EMG) were investigated as potential mediators of RPE during resistance exercise. Twenty female volunteers (age = 25 +/- 4 yrs.) performed one set of biceps curl exercise at 30%, 60% and 90% of their one-repetition maximum (1-RM). Total work was held constant by varying the number of repetitions during each of the three conditions (12 repetitions at 30% 1-RM, 6 repetitions at 60% 1-RM, 4 repetitions at 90% 1-RM). The experimental trials were performed in random order. RPE responses were assessed for both the active muscle (RPE-AM) and the overall body (RPE-O) during each condition. EMG data were collected from the biceps brachii muscle during each condition. Blood samples were taken following each condition and analyzed for blood lactic acid concentration. A two-factor repeated-measures ANOVA showed a significant RPE (region) x Intensity interaction (p < 0.01). Both RPE-AM and (RPE-O) increased as the intensity of exercise increased. A two-factor repeated measures ANOVA performed on the blood [HLa] data showed a significant Time x Intensity interaction. Post-hoc analyses (0.05/3 = 0.0167) showed that the post-exercise [HLa] was significantly greater (p < 0.015) in the 90% 1-RM condition (3.7 mmol·L-1) compared to the 30% 1-RM condition (2.53 mmol·L-1). No significant differences were found in [HLa] between the 30% 1-RM and 60% 1-RM conditions, or between the 60% and 90% 1-RM conditions. A one-factor repeated measures ANOVA on EMG data showed a significant increase in muscle activity as the intensity of exercise increased. These results indicate that monitoring RPE may be a useful technique for regulating resistance exercise intensity. Moreover, blood lactate and activity of the involved muscle may mediate the relation between RPE and resistance exercise intensity.