The Efficacy of Blood Flow Restriction During High Intensity Resistance Exercise

Abstract

Blood flow restriction (BFR) resistance training has demonstrated its effectiveness for inducing hypertrophic adaptations at much lower intensities (20-30% one-repetition maximum (1RM)) compared to traditional high-intensity (>65% 1RM) recommendations. Limited research has examined BFR in conjunction with high-intensity resistance training, with mixed results. The purpose of this dissertation was to expand upon this understudied area with a series of three studies to 1) better understand blood flow responses in the lower limbs with varying occlusion pressures, 2) determine the effect of high-intensity BFR (HI-BFR) resistance exercise on fatigue, ratings of perceived exertion (RPE), and pain, and 3) examine the influence of HI-BFR on metabolic stress, muscle damage, and hypoxia. Study 1 examined the effects of varying BFR occlusion pressures on blood flow volume in the legs. Results indicate a potential 50% limb occlusion pressure (LOP) threshold at which point statistically significant reductions in blood flow volume occur in the posterior tibial artery. An observed plateau in blood flow reductions between 60-80%LOP indicates the potential for reduced occlusion pressure during exercise. Study 2 examined the effects of HI-BFR on inter-set fatigue, RPE, and Pain, in addition to post-exercise neuromuscular fatigue/impairment. Significantly greater number of total repetitions and repetitions during sets 1, 2, and 4 (p < .05) were performed in the CTRL condition. Although RPE between conditions was similar across all sets (p ≥ .05), perceived pain was significantly greater in BFR across all sets (p < .05). Changes in neuromuscular performance measures were consistent across exercise conditions. Study 3 investigated the effect of HI-BFR on metabolic stress, muscle swelling, and muscle damage in response to a back-squat protocol. Significantly lower blood lactate concentrations were measured following the BFR exercise stimulus, compared to CTRL (p = .001). No significant differences in muscle swelling were observed between conditions. Post-exercise interleukin-6 was significantly greater following the BFR exercise (p = .007). The use of BFR during high-intensity resistance exercise seems to be a useful method for advanced induction of fatigue during exercise, although the reduced exercise volume due to fatigue and pain limits the overall acute hypertrophic mechanistic responses.