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Mary A. Wilkenson1, Micaela C. Dusseault1, Katie G. Kennedy2, Ryan J. Colquhoun1. 1University of South Alabama, Mobile, AL. 2Texas Tech University, Lubbock, TX.

BACKGROUND: The purpose of this investigation was to examine the changes in neuromuscular function of the elbow flexors following an acute bout of traditional (TREx) or blood flow restricted (BFR) exercise. METHODS: Eighteen healthy, resistance-trained subjects (7 females) completed one repetition maximum (1RM) testing, as well as two experimental visits. During the experimental visits, subjects completed 4 sets (1x30, 3x15 repetitions) of elbow flexion exercise at 30% 1RM with (BFR) or without BFR (TREx). Thirty seconds of rest was given between each set, and the order of conditions was randomized and counterbalanced across subjects. 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. Prior to and immediately following the exercise bouts, maximal voluntary isometric contraction (MVIC) strength of the participants’ dominant arm was assessed, during which surface electromyography (EMG) of the biceps brachii was recorded. All force and EMG signals were processed offline to calculate peak force (PF), EMG amplitude (EMGAMP), and EMG median power frequency (EMGMDF). RESULTS: There was a significant condition (BFR/TREx) × time (PRE/POST) interaction effect for EMGMDF (p=0.003), but not for PF (p=0.402) or EMGAMP (p=0.330). Post-hoc analyses indicated that EMGMDF significantly decreased from PRE to POST in the BFR condition (PRE: 87.3 ± 23.7 Hz; POST: 68.9 ± 19.0 Hz; p 0.001), but not in TREx (PRE: 80.0 ± 18.4 Hz; POST: 78.9 ± 24.0 Hz; p=0.801). EMGMDF was also significantly greater post-exercise in the BFR condition when compared to TREx (p=0.035). There were simple main effects for time (p<0.001) and condition (p=0.008) for PF and EMGAMP, respectively. When collapsed across time, PF significantly decreased from PRE to POST (PRE: 296.3 ± 97.8 N; POST: 230.5 ± 68.2 N; p<0.001). When collapsed across condition, EMGAMP was significantly greater during TREx when compared to BFR (TREx: 0.26 ± 0.12 mV; BFR: 0.22 ± 0.10; p = 0.008). CONCLUSIONS: The results of the present investigation suggest that neuromuscular fatigue and decrements in PF are similar following acute bouts of BFR and TREx of the elbow flexors. However, EMGMDF significantly decreased following BFR, but not TREx, suggesting that the mechanisms of fatigue may differ between modalities.

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