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Keith S. Saffold1, Bjoern Hornikel1,2, Lee J. Winchester1. 1The University of Alabama, Tuscaloosa, AL. 2The University of Alabama at Birmingham, Birmingham, AL.

BACKGROUND: Blood flow restriction (BFR) training has been shown to increase hypertrophy at low resistance loads, to a similar extent as observed in high resistance loads, likely as a result of metabolic stress. However, the effects of BFR use have focused largely on muscular performance around the site of occlusion, with little information on the tissue distal to the occlusion site. The effect of direct tissue compression may play a significant role in the effects of BFR. Therefore, the purpose of this study was to analyze the effects of BFR training on indices of muscular performance in non-compressed muscle tissue distal to the site of occlusion. METHODS: Participants (N = 20; M±SD: 23.0 ± 3.8 years; 174.1 ± 9.0 cm; 77.9 ± 13.0 kg; 23.8 ± 8.6%body fat) completed a baseline visit and two experimental conditions consisting of exercise only (control; CON) and exercise with BFR. CON and BFR were performed in a counter-balanced order. Personal tourniquet pressure (PTP) was determined in each leg using the Delfi PTS II system for the BFR session only. The following assessments occurred pre and post each visit: anatomical cross-sectional area (CSA) of the gastrocnemius, toe tap test, average stride length test, and counter-movement jump. The exercise protocol consisted of 3 sets of 15 repetitions of ankle plantarflexion (PF) and dorsiflexion (at 60 and 500 degrees per second, respectively) on the dominant limb, using an isokinetic dynamometer, which also measured average force and total work per set. BFR application during the exercise protocol consisted of unilateral occlusion at 80% of PTP, applied 30 s before initiating exercise on each leg, at the proximal thigh. Two-way repeated measures analysis of variance (ANOVA) was performed to determine if changes in CSA, and measures of muscular strength and performance differed by BFR application (condition × time). Significance was set as p<0.05. RESULTS: CSA was increased post- versus pre-exercise following BFR compared to CON. Toe taps and stride length performance were decreased post- versus pre-exercise following BFR compared to CON. Jump height decreased post- compared to pre-exercise with no difference between conditions. Average force and total work were both significantly lower in the BFR trial. CONCLUSIONS: The addition of BFR to the quadricep during exercise elicited higher levels of muscular fatigue and decreased recovery rate in the calf musculature.

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