Acute Effects Of Blood Flow Restriction Resistance Exercise On Microvascular Reactivity

Chronic blood flow restriction (BFR) resistance exercise has demonstrated improvements to muscular strength, hypertrophy, and microvasculature function. However, the acute microvascular effects are unknown. Microvascular function can be assessed using near-infrared spectroscopy (NIRS) measuring skeletal muscle oxygen (SmO2) resaturation rate (i.e., slope) following a vascular occlusion test (VOT). PURPOSE: To compare the effects of a single BFR resistance exercise session and a traditional resistance exercise (TRE) session on acute microvascular reactivity in an exercising and non-exercising muscle. METHODS: Twenty-five adults (M = 14, F = 11, age: 22 ± 3 yrs, body mass: 71.7 ± 14.5 kg, height: 170 ± 10 cm) completed barbell back squat 1 repetition maximum (1RM) testing followed by two randomized and counterbalanced resistance exercise visits separated by ≥48 hrs. Exercise visits used the barbell back squat adhering to either BFR; (4 sets of 30-15-15-15 repetitions at 30% 1RM, with 60s of rest intervals), or TRE; (4 sets of 10 repetitions at 70% 1RM, 60s of rest intervals). During all pre- and post-VOTs, NIRS devices continuously recorded SmO2 in the vastus lateralis (VL) and flexor carpi radialis (FCR). RESULTS: Two-way repeated measures ANOVA found an interaction effect (p = 0.020) for SmO2 reactivity in the VL (pre-TRE 2.94 ± 1.10; post-TRE 3.11 ± 1.30; pre-BFR 2.64 ± 1.00; post-BFR 3.74 ± 1.23). Post hoc analysis found greater reactivity post-exercise in the VL for the BFR condition (p < 0.001), but not the TRE condition (p ≥ 0.05). There were no time, condition, or interaction effects (all p > 0.05) for the same analysis in the FCR. CONCLUSION: BFR, not TRE, resulted in acutely improved microvasculature function. These effects of BFR are local to the exercised/occluded limb and not systemic.