A hot new topic in strength training is blood flow restriction (BFR), or limiting the venous return of blood flow from the muscle. The goal is not to restrict arterial blood flow but prevent the return of blood flow to the muscle, typically by tightly wrapping limbs to cause the blood to pool in the muscle during exercise.
One of the leading researchers on the topic is Dr. Jeremy Loenneke, an assistant professor of exercise science at The University of Mississippi who does research in skeletal muscle physiology. He’s completed research on BFR and how it may be used to reduce atrophy and/or aid in muscle growth when it is combined with low load resistance training. During an e-mail exchange, I asked Dr. Loenneke to lay out the basics about BFR.
Michael Joyner: What is the basic idea and history behind BFR? Didn’t it start in Japan?
Dr. Jeremy Loenneke: The first study on blood flow restriction (BFR) training was published in 1998. This concept appears to have originated in Japan and it involves partially restricting blood flow into the muscle (arterial flow) and occluding blood flow out of the muscle (venous return). This style of training has been shown to have beneficial effects to skeletal muscle and possibly bone.
MJ: A lot of ideas about training recycle over time. My sense is that BFR is something new, or is it an old concept that is being recycled?
JL: “Ischemic exercise” was a concept that was around before BFR training became popular, but that research was predominately focused on endurance performance. The idea of applying a cuff to induce changes in skeletal muscle size and strength came a bit later.
MJ: Reading the scientific papers it seems like you can get pretty impressive increases in muscle size and strength with BFR and light weights. How light can you go?
JL: Studies have found that lifting as low as 20% of maximum strength can produce increases in muscle size and strength similar to that of traditional resistance exercise which uses closer to 70% of an individual’s maximum strength. The beneficial effects have primarily been noted in muscles under direct BFR (e.g. arms and legs), however, there is some data that suggests that skeletal muscle not directly affected by the cuff may also benefit.
For example, a handful of studies have found that doing the bench press with cuffs applied to the top of the arm, increases muscle size and strength despite the chest not being under BFR. The mechanism behind this “indirect” effect of BFR is not known, but may be related to the fatiguing of the triceps.
MJ: Some techniques that work in novices don’t work as well in experienced lifters and strength trainers. Does BFR work in those groups?
JL: BFR in combination with low load resistance training has been shown to have beneficial effects to skeletal muscle in both trained and untrained populations, young and old alike. There is also some evidence that low intensity walking—less than 2 mph—with BFR can increase muscle size in novice individuals, but we have not been able to show this consistently in more active people.
MJ: Do the increases in muscle mass with BFR translate into strength gains?
JL: Increases in muscle strength do occur with BFR training, however, the law of specificity still applies. For example, muscular strength increases in the exercise that is used for training, but it tends to be a bit lower with low load BFR exercise when compared to traditional high load exercise, due to repeated practice of lifting heavy in that exercise. When looking at a more objective strength test—one not repeatedly practiced by either group—strength is usually identical.
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MJ: Are there any safety concerns or groups of people who should not be using BFR?
JL: Muscle damage and blood clotting are two of the concerns that many people initially have with this type of training. Muscle damage does not appear to occur to a measurable degree with this type of exercise, probably because of the low loads used and the short duration that the partial BFR is applied (e.g. less than 5-10 minutes). In addition, the system responsible for blood clotting does not appear to be activated with low load resistance exercise in combination with BFR. Although this stimulus has been shown to be relatively safe, there are some populations that may want to use caution prior to trying BFR. For example, those who may be at an elevated risk for blood clots may want to be careful with this type of training. In addition, those who many have had lymph nodes removed may not want to use BFR on the affected limb.
MJ: Can you point readers to some web based resources for those interested in trying BFR?
JL: Here are a few resources. The first is a guide to “Practical Blood Flow Restriction” and the second is from Ole Miss where we have provided a summary for the majority of the published literature on BFR.
I have been involved in exercise research and thinking about training since the late 1970s. Almost every next big thing I see or hear about is in fact a collection of older ideas that are being recycled. BFR original and the links above will let you do it in a smart way.
Michael Joyner, is an expert in human performance at the Mayo Clinic, these views are his own. You can follow him on twitter @DrMJoyner.