Micaela C. Dusseault, Mary A. Wilkenson, Katie G. Kennedy, Ryan J. Colquhoun. University of South Alabama, Mobile, AL.

BACKGROUND: The purpose of this investigation was to examine ratings of perceived exertion/repetitions in reserve (RPE/RIR) and repetitions completed across 4 sets of traditional (TREx) or blood flow restricted (BFR) exercise of the elbow flexors. METHODS: Eighteen healthy, resistance-trained subjects (7 females) completed this randomized, counterbalanced trial. Subjects completed one repetition maximum (1RM) testing, as well as two experimental visits, in which they completed 4 sets (1x30, 3x15 repetitions) of elbow flexion exercise at 30% 1RM with (BFR) or without BFR (TREx). 30 seconds of rest was given between each set. All visits were separated by at least 48 hours and took place at the same time of day (±1 hour). For the BFR condition, the cuffs were rapidly inflated to 60% arterial occlusion pressure. Immediately following each set, an RPE/RIR score was assessed. Repetitions completed was also calculated for each set. RESULTS: There was a significant condition (BFR/TREx) × set (S1/S2/S3/S4) interaction effect for RPE/RIR score(p=0.016) and repetitions completed (p<0.001). Post-hoc analyses indicated that in the TREx condition, RPE/RIR non-significantly increased from S1 (7.1 ± 1.5 au) to S2 (7.5 ± 1.3 au; p=0.095) and significantly increased from S2 to S3 (8.1 ± 1.4 au; p<0.001) and S3 to S4 (8.6 ± 1.5 au; p<0.001). Similarly, RPE progressively increased in the BFR condition and was significantly different at all timepoints (S1: 7.7 ± 1.3 au; S2: 8.9 ± 1.0 au; S3: 9.6 ± 0.7 au; S4: 9.8 ± 0.4 au; p<0.001-0.028). During all except S1 (p=0.119), RPE/RIR was significantly greater in the BFR condition when compared to the corresponding TREx set (p<0.001 for all). In S1, subjects completed all 30 repetitions in both conditions. Thus, S1 had significantly greater repetitions in both conditions when compared to all other sets (p<0.001 for all). Post-hoc analyses indicated that in the BFR condition, subjects completed significantly more repetitions in S2 (14.2 ± 2.3 reps) when compared to S3 (11.4 ± 4.6 reps; p=0.009) and S4 (10.3 ± 4.8 reps; p=0.001). There were no significant differences between S2-S4 in the TREx condition (p=0.177-0.999) or between S3 and S4 in the BFR condition (p=0.251). Significantly more repetitions were completed during TREx in S3 (15.0 ± 0 reps; p=0.004) and S4 (14.6 ± 1.3 reps; p=0.002) when compared to BFR. CONCLUSIONS: Our data suggest that the addition of BFR to a low-load exercise bout of the elbow flexors significantly increases RPE/RIR and diminishes the number of repetitions that can be completed in resistance-trained subjects.

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