Drake A. Eserhaut1, Joseph M. DeLeo1, & Andrew C. Fry1

1Jayhawk Athletic Performance Laboratory – Wu Tsai Human Performance Alliance

University of Kansas, Lawrence, Kansas

Few published data exist on how continuous lower-limb blood flow restriction (BFR) alters skeletal muscle oxygen saturation (SmO2) in well-resistance trained men. PURPOSE: Compare SmO2 kinetics during passive lower-limb BFR (pBFR), BFR resistance exercise performed to muscle failure (BFR+RE), and volume-matched free-flow resistance exercise (RE). METHODS: Nineteen resistance trained men (x̄±SD: age=23.68±3.42yr; mass=90.28±15.55kg; relative back squat 1RM: 1.91±0.33kg/bw) reported for four separate visits. First, body composition, blood pressure, back squat and leg extension one-repetition maximums (1RM) were assessed. Resting systolic blood pressure and proximal thigh circumferences were used to estimate the pressure needed for full arterial occlusion (eAOP). Visit two involved pBFR, where pneumatic BFR cuffs were inflated to 80% eAOP around the proximal thighs for 10-minutes while participants were seated in a leg extension machine. Then, 24-120hr later participants performed four sets of bilateral seated leg extensions at 30% 1RM for four sets to muscle failure with 1-minute rest intervals while under the same 80% eAOP. After 72-120hr rest, participants matched the repetition performances from BFR+RE for the volume-matched, free-flow resistance exercise trial. A portable NIRS device was affixed onto the right vastus lateralis in all trials. SmO2 re-saturation rate (SmO2slope) was calculated from the upslope during the first 30-seconds of each rest period. RESULTS: Minimum SmO2 values were greater at all four pBFR time-points (2.5, 5, 7.5, and 10min) compared to intra-set SmO2 during BFR+RE and RE (p<.001). No differences in minimum intra-set SmO2 values were present between BFR+RE and RE. RM-ANOVA indicated significant differences in SmO2slope between BFR+RE and RE (p<.001). SmO2slope was significantly lower in BFR+RE during all four rest periods (Rest 1: MD=-0.36; Rest 2: MD=-0.44; Rest 3: MD=-0.43; Rest 4: MD=-0.27%•sec-1), compared to RE. CONCLUSION: Continuous BFR+RE significantly blunts the recovery of SmO2 during 1-minute rest intervals compared to volume-matched free-flow training, indicating a hindered ability to re-oxygenate skeletal muscle. Future work comparing BFR+RE to heavy load training (70% 1RM) in well-trained populations is warranted to further these findings.

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