The Application of Blood Flow Restriction Training into Western Medicine: Isn't It About Time?

T o remain functionally independent and healthy, an important factor to consider is the maintenance of skeletal muscle mass. After surgery, the application of acute blood flow restriction (BFR) in the absence of muscle contraction has previously been demonstrated to attenuate muscle atrophy. ¹ In addition, significant muscle hypertrophy occurs when BFR is combined with low-intensity aerobic-type exercise or low-load resistance training. ^2,3 The low intensity/low load used with BFR makes this mode of exercise appealing to patients who may not be able to sustain the higher levels of stress associated with higher-intensity, higher-load exercise. Furthermore, a comprehensive review of the literature suggests that BFR can applied safely, across a variety of populations. ⁴ A common concern is the risk of activating the coagulation system through the restriction of venous return; however, this system has not been activated with BFR in combination with resistance exercise in a healthy population or those with ischemic heart disease. ^5,6 In contrast, fibrinolytic activity was actually increased during BFR resistance exercise. ⁵

This commentary seeks to better familiarize the medical community about BFR and discuss its potential application in Western medicine. The article briefly outlines the proposed mechanisms behind the positive effects observed with BFR. It also provides rationale for the application of BFR by briefly discussing specific studies and cases where BFR, in the absence of exercise or in combination with muscle contraction, resulted in positive adaptations to skeletal muscle in patients who were injured or diseased.

Numerous long-term studies have shown that BFR by itself or in combination with exercise positively affects skeletal muscle without negatively affecting health. ⁷ For example, Takarada et al. ¹ observed that the application of BFR in the absence of exercise slowed the rate of atrophy after anterior cruciate ligament reconstruction compared with a group undergoing standard care. This is significant because muscle mass is important for metabolism and maintaining a high quality of life. In addition, Ozaki et al. ³ found that when elderly men and women slowly walked on a treadmill under BFR, muscle hypertrophy and strength increased without negatively affecting arterial compliance. This study demonstrates that the application of BFR to an activity of daily living, such as walking, may be beneficial and safe for those unable to perform or uncomfortable performing high-load resistance training. The response to BFR in combination with low-load resistance training produces an even greater response in muscle hypertrophy and strength gain compared with walking plus BFR, and this has even been observed in a patient with idiopathic inflammatory myopathy. ⁸ Because of this myopathy, the patient could not train with the higher loads typically required to maintain skeletal muscle health. When the patient started performing low-load resistance exercise in combination with BFR, muscle function and quality of life improved, with no disease flare-up. Together, these findings suggest that BFR alone or in combination with exercise may be an important tool in the maintenance or accrual of skeletal muscle in healthy and at-risk populations.

A commonly cited reason for not implementing BFR in at-risk populations is that the exact mechanism of action behind the increase in muscle mass is unknown. However, there are numerous pharmaceutical drugs prescribed daily in which the exact mechanism of action is unknown (such as acetaminophen and metformin); therefore, this argument seems moot. BFR alone or in combination with slow aerobic exercise has been hypothesized to attenuate atrophy through fluid shift–induced muscle cell swelling, which may provide the stimulus for increased anabolic or anticatabolic signaling. ⁹ The magnified effect on skeletal muscle hypertrophy from low-load resistance training with BFR is probably due to muscle cell swelling and additional mechanisms. This mode of BFR has been the most extensively studied, and it is known that BFR resistance exercise stimulates muscle protein synthesis. ¹⁰ However, as is the case with higher-load resistance training, there is debate as to the exact cellular mechanisms associated with the enhanced protein synthetic rate. One possibility is that low-intensity resistance exercise combined with BFR produces a metabolic “overload” (i.e., depletion of phosphocreatine stores and decrease in muscle pH) normally associated with higher muscle activations observed during high-intensity resistance exercise. ^11,12 Furthermore, it has recently been observed that the benefits of BFR in combination with resistance exercise may, in part, be related to the concomitant decrease in the messenger RNA gene expression of the E3-ligases (MURF-1, Atrogin) and myostatin ^2,13 and increases in the messenger RNA gene expression of the follistatin isoforms. ²

In conclusion, it appears that BFR alone or in combination with exercise potentially offers a valuable tool for improving or maintaining skeletal muscle health. Although the research initially focused on healthy people, several recent studies completed in more at-risk populations have also shown improvements in skeletal muscle mass without negative health consequences. The time may be arriving for Western medicine to seriously consider the application of BFR by itself or in combination with exercise for patients who are unable to perform higher-intensity, higher-load exercise.