By Robert Crandall, SPT
Blood flow restriction (BFR) training is a hot topic in both the fitness and health care world right now due to its ability to increase strength and muscular hypertrophy more quickly than traditional progressive resistance exercise. It is performed by the occlusion of blood circulation, with either a blood pressure cuff or elastic bands placed proximally on the limb, in a working muscle group while performing resistance exercises. The objective of BFR is to occlude venous blood return without significantly affecting arterial circulation. In this way, blood enters into the muscle but cannot escape until the pressure of the restricted implement is released. The pressure used with blood pressure cuffs is typically placed at a pressure between 50-80% of the pressure for which it takes to stop arterial flow into the limb. When using elastic wraps or tourniquets, which were found to be as effective as blood pressure cuffs, should be placed at a subjective 7/10 tightness level.
Many research articles are being published about the strength and muscle enhancing effects of performing this novel type of resistance training. There are clinical trials that show that blood flow restriction alone, without any resistance, or even muscular activation of the limb, can be effective enough to decrease the typical muscular atrophy and diminished strength subsequently following the immobilization of a limb in a cast. The research also boasts larger strength gains for untrained individuals with restricted blood flow and low load exercise performed with low resistance loads (20-40% of MVIC or 1RM) for 3-4 sets with a total of 50- 80 reps performed total. These sets are done with limited rest between them, 30-45 seconds, 2-4 times a week. This is particularly beneficial for individuals who cannot tolerate the typical training with 70% of MVIC required to increase muscular strength. The research even shows decreased metabolic stress factors and joint compressive forces while using blood flow restriction training as compared to traditional strength training.
For athletes, even as well trained as at the collegiate level there is a benefit to the addition of blood flow restriction training to their normal strength training programs. Studies have shown increased bench press and squat 1RM in division 1A football players as well as faster sprinting times in collegiate track athletes. For these well trained individuals they should perform the blood flow restriction training described above following their typical high load resistance training for maximum benefits.
The mechanisms for which blood flow restriction training work through include increased accumulation of metabolites in the muscle tissues causing a larger decrease in the local pH which in turn increases the overall excitability of the afferent nerves in the local musculature. Meaning that muscular fibers require less overall stimulus for activation, thus increasing the number of muscle fibers stimulated during a muscular contraction by amplifying the signals sent from the central nervous system.The restricted flow of blood also increases the levels of muscle building hormones like free testosterone and IGF-1 in the muscle tissue as compared to typical progressive resistance exercise.
With all of these benefits the use of blood flow restriction training should only steadily increase, especially as more and more clinical research is performed. Although due the increased demands placed on the peripheral vasculature of the limbs being trained, people with a history of DVTs, who are pregnant, who have cardiovascular disease, diabetes, cancer, or peripheral vascular disease are generally contraindicated from participating in blood flow restriction training.
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