Blood flow restriction training (BFR)

Blood flow restriction (BFR) training puts a cuff, bandage or wrap around the top of a limb during a lift.^{1Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 124.} The wrap limits blood flowing out of the muscle. Blood can still flow in.^{1Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 124.} Israetel and colleagues call this occlusion training.^{2Israetel et al., Scientific Principles of Hypertrophy Training, p. 80.}

With less blood leaving, the byproducts of muscle work, called metabolites, can’t clear out.^{1Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 124.} Muscle fibers start working sooner and tire sooner.^{1Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 124.} Some researchers think this metabolic stress is what drives the growth.^{3Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd ed., p. 50.}

The big draw is the light load. With BFR, loads as low as 20 to 30% of 1RM can build muscle as well as heavier loads.^{1Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 124.} They don’t build strength as well, though, and they aren’t better for growth.^{1Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 124.} Done regularly, BFR can add a lot of muscle, often about as much as heavy loads.^{4Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd ed., p. 57.}

Because the loads are light, BFR is thought to cause little muscle damage. But some studies have found signs of damage after it, such as long-lasting strength loss and more soreness.^{4Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd ed., p. 57.}

In practice

• Helms suggests BFR when knee or elbow pain gets in the way. The light load keeps a muscle stimulus and may help the joint recover.^{1Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 124.}
• Helms applies it to single-joint exercises. Wrap to about 7 out of 10 tightness.^{1Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 124.}
• Tingling, or a limb that turns purple, means the wrap is too tight.^{1Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 124.}
• Do the usual number of sets, taken to failure, at 20 to 30% of 1RM.^{1Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 124.}
• It only suits muscles whose blood flow can be cut off. You can’t do much to stop blood flow to the back or abs.^{5Israetel et al., Scientific Principles of Hypertrophy Training, p. 81.}
• Use it sparingly, and save it for late in the session.^{5Israetel et al., Scientific Principles of Hypertrophy Training, p. 81.} It can help keep muscle during injury recovery or a hard contest diet.^{5Israetel et al., Scientific Principles of Hypertrophy Training, p. 81.}

Where sources differ

The sources give different load ranges. Helms gives 20 to 30% of 1RM.^{1Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 124.} Israetel and colleagues say loads as light as 20% can be used.^{5Israetel et al., Scientific Principles of Hypertrophy Training, p. 81.} Schoenfeld gives 20 to 50% of 1RM in one passage^{4Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd ed., p. 57.} and generally under 40% in another.^{3Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd ed., p. 50.} Israetel and colleagues also think BFR is unlikely to grow the fastest muscle fibers as much as possible.^{5Israetel et al., Scientific Principles of Hypertrophy Training, p. 81.}