How it Works
Similar to strength and hypertrophy training where blood flow restriction elicits high load adaptations at low actual training loads, the application of BFR seems to mimic high intensity aerobic adaptations at low to moderate intensities. The effects of blood flow restriction training on aerobic capacity have been well studied, with a robust amount of research demonstrating favorable improvements in VO2 max after implementing it into training regimens.
Without the application of BFR, individuals generally must incorporate activities at 70% or more of their maximal oxygen consumption (VO2 max) to achieve a significant training effect. However, occluding blood flow the working muscle during low to moderate intensity aerobic exercise triggers a cascade of physiological responses that lead to endurance improvements comparable to high intensity training. Some of these physiological responses are outlined below.
- Hypoxia - This is a state of low oxygen in the working muscle. During high intensity aerobic training, muscle demand for oxygen exceeds the amount it is able to uptake, creating a hypoxic environment. In the context of BFR, because a large percentage of oxygen-carrying blood flow to the limb is occluded, a hypoxic environment is created with much less exercise intensity. Exercise-induced local hypoxia is known to elicit favorable adaptations in endurance.
- Metabolite accumulation - Lactate accumulation occurs to a significant degree in high intensity aerobic exercise. Continual exposure to this stimulus is known to result in favorable changes in lactate threshold. With occlusion applied, lactate clearance is limited, resulting in lactate increases consistent with high intensity exercise (despite training at low to moderate intensities). This can be an energy-sparing method of training to increase lactate threshold.
- Cardiac Output - Decreases in the amount of blood flow reaching the working muscles causes a concomitant increase in heart rate as a physiological compensation. This in turn can create similar heart rate increases as higher intensity exercise while at a low or moderate intensity. Ultimately, this can replicate some of the cardiac benefits of more strenuous exercise without the physical demands of high intensity training.
Though there are hundreds of peer-reviewed papers on blood flow restriction, the scientific community heavily values systematic reviews and meta-analyses, which examine data from multiple independent and high quality studies to determine overall trends. The below systematic review includes 14 different studies examining the impacts of blood flow restriction on endurance.
Effects of blood flow restriction training on aerobic capacity: a systematic review and meta-analysis
“BFR training compared with exercise under normal blood flow conditions could positively influence both aerobic capacity and athletic performance. Differences in young and older subjects were discussed. BFR showed to be a promising and beneficial training to elicit improvements in aerobic capacity (measured in VO2) and performances.”
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