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Department of Kinesiology and Integrative Physiology
PhD Defense

Acute and Chronic Responses to Exercise with Blood Flow Restriction

ABSTRACT: Exercise with blood flow restriction (BFR) allows healthy, clinical, and athletic populations to improve their muscle size, strength and exercise capacity at low training intensities. Currently, there are no standardized guidelines for prescribing exercise with BFR. In this series of studies, I used a variety of experimental techniques including ultrasound, near-infrared spectroscopy, expired air analysis, electrical stimulation, and dual-energy X-ray absorptiometry with the goal of investigating how cuff pressure and as well as the type of exercise alter acute and chronic responses to exercise with BFR. In study 1, participants completed resistance exercise at various cuff pressures during which arterial blood flow and tissue perfusion were measured. My key finding was occlusion pressures ranging from 60-80% LOP provided considerable metabolic stress while still maintaining partial arterial blood flow, thus lowering the relative risk of adverse cardiovascular responses to exercise with BFR. In study 2, I evaluated cardiorespiratory, metabolic, neuromuscular, and perceptual responses before and after aerobic exercise with BFR. Participants completed four cycling conditions with and without BFR. I found cuff pressures of ~60% limb occlusion pressure reduced arterial blood flow by ~33%, and tissue perfusion by ~5%, without increasing cardiovascular strain, or effort to that of high intensity cycling. Additionally, knee extensor torque in the BFR conditions was compromised through a combination of peripheral and central mechanisms. Finally, in study 3, I evaluated differences in muscle size, strength, and exercise capacity following 6 weeks of either aerobic or resistance training with BFR. I found aerobic exercise with BFR may be more favorable than resistance exercise because it results in similar increases in muscle size (4-7%) and strength (8-15%), but at a lower rating of perceived effort (8.6 vs. 11.0 respectively) and pain (mild pain vs. moderate pain respectively). Moreover, aerobic training lead to a 5% increase in VO2max, whereas there was no change in the resistance group. Taken together, findings from this series of studies will aid researchers, clinicians, and coaches to more safely and effectively prescribe exercise with BFR to improve muscle size, strength and exercise capacity.