Muscle weakness is a common problem faced by many. Although high intensity exercise is the most common way to tackle this issue, for some individuals, it is simply impossible to perform rigorous exercise at this level of intensity. These include individuals who suffer from chronic diseases, post-operative injuries, and post-acute injuries . For this select population to achieve muscular hypertrophy and higher strength, blood flow restriction (BFR) training has gained popularity among physical therapists and fitness enthusiasts. In BFR training, low load resistance training is paired with blood flow restriction to achieve results that are comparable to high resistance training .
Low load training combined with blood flow restriction, or LL-BFR training, requires a tourniquet-style cuff which is applied to the target limb before exercising. The goal of the cuff is to exert enough pressure to restrict venous blood flow while still allowing arterial inflow. After the correct pressure is set on the cuff, patients can begin their workout. Patients are able to perform low load resistance exercises as low as twenty percent of their regular 1-RM (1-repetition max) strength, and according to research, this is enough to observe an improvement in muscular strength . Clinicians recommend high repetition and volume with LL-BFR training, with patients completing 75 repetitions divided into four sets. Patients should train on average two to three times a week .
Several physiological factors contribute to the efficacy of BFR training. BFR training allows the patient to experience high intensity exercise by creating an environment with limited oxygen flow. Blood near the cuff is low in oxygen, resulting in the activation of hypoxia-inducible factor (HIF-1α). This activation causes muscles to switch to anaerobic lactic metabolism. Consequently, lactic acid builds up, producing effects similar to that of high intensity training . The presence of the cuff is also responsible for higher muscle tension, which then activates myogenic stem cells; these cells are critical for muscle fiber repair and growth. Furthermore, the cuff drastically decreases outgoing blood flow from the limb, forcing blood to accumulate and pool in the vicinity. The accumulation of blood and metabolites causes cell swelling to take place, which is known to achieve muscle hypertrophy .
A study conducted by Sousa et al. assigned participants to four experimental groups. With all other factors held constant, group one engaged in high intensity training, group two engaged in low intensity training, group three engaged in high intensity training in addition to LL-BFR training, and group four engaged in LL-BFR only. The researchers concluded from this study that groups one, three, and four saw significant increases in muscle size and strength. Interestingly, results were comparable among these three groups, demonstrating the high efficacy of LL-BFR . Reports and surveys on BFR indicate that it is a safe technique for patients across different age groups. Older patients have even demonstrated muscle hypertrophy when performing very low intensity exercises such as walking paired with BFR . Blood flow restriction training provides a safe solution to muscle strengthening for those who are unable to perform high intensity exercises.
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