Investigating the Effects of Aerobic Exercise with Blood Flow Restriction on Vastus Lateralis Muscle Oxygenation
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Blood flow restriction training (BFRT) is a novel adaptation to traditional forms of aerobic or resistance exercise. By restricting blood flow to the active skeletal muscles, previous research has demonstrated that it can induce similar benefits to musculoskeletal health as non-blood flow restricted (BFR) exercise, despite exercising at lower intensities and for a shorter duration of time. The mechanisms through which BFRT stimulates physiological adaptations remains uncertain however, one proposed stimulus is localized skeletal muscle hypoxia. This thesis aimed to investigate this stimulus by assessing muscle oxygenation during low-intensity aerobic exercise with BFR. Vastus lateralis oxygenation was assessed using continuous-wave near-infrared spectroscopy in 15 participants (n=15) during 20 minutes of BFR and non-BFR exercise sessions. Significant differences in muscle tissue oxygenation was observed (P<0.001) indicating that BFR during low-intensity walking exercise reduced muscle oxygenation more so than non-BFR exercise. Furthermore, significant differences in total hemoglobin (THb) and deoxygenated hemoglobin (HHb) were observed (P<0.05 and P<0.001, respectively), such that THb and HHb were significantly greater during BFR-exercise versus non-BFR exercise. Oxygenated hemoglobin (O2Hb) on the other hand, was not significantly different between exercise sessions. These findings suggest that BFR during low-intensity aerobic exercise may induce a localized hypoxic response in the skeletal muscle tissues distal to the cuffs. The reduction in muscle oxygenation in the presence of increased tissue blood volume may suggest that BFRT influences oxygenation by moderating blood flow through the active skeletal muscle tissues during exercise.