Assessment of Performance Fatiguability During Resistance Exercise Anchored to Ratings of Perceived Exertion

Abstract

PURPOSE: According to the critical threshold hypothesis, fatiguing single-leg exercise at intensities above the critical force should result in performance fatiguability that is unvarying. The purpose of the present study was to examine the fatigue-related decreases in maximal voluntary isometric contractions (MVIC) as an indirect measure of performance fatiguability at intensities anchored by ratings of perceived exertion (RPE). METHODS: Ten recreationally-active men (22.9 ± 2.0 yr) performed 3 randomly ordered, sustained submaximal isometric leg extension muscle actions anchored to RPE values of 2, 5, and 8 (OMNI-RES 10-point scale) until the RPE value could no longer be maintained or a maximal time-limit of 5-min was reached. The percent decline in MVIC was defined as the difference between pretest and posttest values. A 1×3 repeated measures ANOVA was used to examine mean differences in MVIC percent decline values at RPE=2, 5, and 8. RESULTS: The mean (±SD) actual time-limits for the sustained muscle actions anchored to RPE=2, RPE=5, and RPE=8 were 300.0 ± 0.0 s, 202.0 ± 95.5 s, and RPE 8 = 72.7 ± 27.6 s, respectively. The pretest to posttest decreases in MVIC values for RPE=2, 5, and 8 were 61.9 ± 14.3 to 42.8 ± 11.4, 62.4 ± 14.3 to 47.9 ± 12.8 and 63.0 ± 12.6 to 54.0 ± 14.7 kg, respectively. There was a significant (p=0.023) difference in MVIC percent decline, and the pairwise comparisons indicated that the percent decline in MVIC was significantly (p<0.001) greater for RPE=2 (30.4 ± 11.6 %) than RPE=8 (15.1 ± 13.6%), but there were no differences (p>0.05) for RPE=5 (22.0 ± 14.0%) versus RPE= 2 or 8. CONCLUSIONS: In general, the similar MVIC percent decline values at RPE=5 and 8, as well as the greater percent decline at RPE=2, supported the critical threshold hypothesis. Furthermore, performance fatiguability as assessed from MVIC measurements followed the expected pattern of responses as those previously described for involuntary potentiated twitch amplitude. These findings also suggested that RPE=2 was below critical intensity, but RPE=5 and RPE=8 were not.