Blood Flow Restriction Training Primer
Blood flow restriction (BFR) training allows for the use of low loads (20-30% of concentric 1-repetition maximum [1RM]) to induce muscular hypertrophy and strength gain (Loenneke et al., 2012). BFR involves the application of an inflatable cuff to the most proximal portion of an extremity and inflated to 40%-80% of the pressure necessary to achieve full arterial occlusion for the individual (Patterson et al., 2019). Under such conditions, venous outflow becomes severely restricted and capillary blood pooling occurs; the reduction in venous return results in localized muscle hypoxia (Patterson et al., 2019). The ischemic environment increases metabolic stress, a main mechanism for inducing muscular hypertrophy (Pearson & Hussain, 2014).
Mechanical tension, metabolic stress, and muscle damage are main mechanisms of exercise-induced muscle growth (Schoenfeld, 2010). The ischemic environment created in the muscle with the application of BFR augments both metabolic stress (increased metabolite accumulation) and several secondary mechanisms of hypertrophy including greater fast-twitch fiber recruitment, cellular swelling, increased reactive oxygen species production, and increased satellite cell activation and proliferation (Pearson & Hussain, 2015). As the loads used in conjunction with BFR training are low (20%-30% 1RM), it is suggested that metabolic stress plays the dominant role in hypertrophic adaptations to BFR training with mechanical tension playing a secondary synergistic role; muscle damage does not appear to occur to a large extent (Patterson et al., 2019).
Loss of muscle mass and strength is of concern with older populations, severe injury, and those with chronic diseases. It is important to maintain or improve skeletal muscle mass and strength to improve outcomes and expedite recovery in these populations. However, high load resistance training is often contraindicated due to comorbidities or an inability for injured joints to withstand the loads required for hypertrophy with high load resistance training. BFR has been shown to achieve the same hypertrophic benefits as high load resistance training (Dankel et al., 2016). Additionally, growth has been observed for muscles not under direct BFR (proximal to applied cuff) and muscle mass preservation with passive restriction (Patterson et al., 2019). Blood flow restriction appears to be safe for elderly, injured, and diseased populations without risk factors for venous thromboembolism (Loenneke et al., 2011).
References
Dankel, S. J., Jessee, M. B., Abe, T., Loenneke, J. P. (2016). The Effects of Blood Flow Restriction on Upper-Body Musculature Located Distal and Proximal to Applied Pressure. Sports Medicine, 46, 23-33.
Loenneke, J. P., Wilson, J. M., Wilson, G. J., Pujol, T. J., Bemben, M. G. (2011). Potential Safety Issues with Blood Flow Restriction Training. Scandinavian Journal of Medicine & Science in Sports, 21, 510-518.
Loenneke, J. P., Wilson, J. M., Marin P. J., Zourds, M. C., & Bemben, M. G. (2012). Low Intensity Blood Flow Restriction Training: A Meta-Analysis. European Journal of Applied Physiology, 112, 1849-1859.
Patterson, S. D., Hughes, L., Warmington, S., Burr, J., Scott, B. R., Owens, J., Loenneke, J. (2019). Blood Flow Restriction Exercise Position Stand: Considerations of Methodology, Application, and Safety. Frontiers in Physiology, 10, 1-15.
Pearson, S. J. & Hussain, S. R. (2015). A Review on the Mechanism of Blood-Flow Restriction Resistance Training-Induced Muscle Hypertrophy. Sports Medicine, 45, 187-200.
Schoenfeld, B.J. (2010). The Mechanisms of Muscle Hypertrophy and their Application to Resistance Training. Journal of Strength and Conditioning Research, 24(10), 2857-2872.