October, 2018: Blood Flow Restriction Therapy, Part I: The Basics and Use in Normal Individuals
Rather than discuss one article as usual, for this month and next, I will discuss one topic with information drawn from the above five journal articles.
Blood flow restriction (BFR) (also known as Kaatsu) training originated in the 1990s in Japan. After kneeling in front of a Buddha statue, the originator noted a tingling sensation in his leg that was similar to the sensation he experienced after weight training. The widespread acceptance and use among weightlifters and athletes, however, is a relatively recent occurrence.
Conventional strengthening techniques require the trainee to load a muscle group to at least 70% of its one-repetition maximum to achieve noticeable improvements in muscle strength and mass over time. In multiple studies, investigators have shown that by placing a venous tourniquet as proximally as possible on either the upper or lower limb, blood accumulates distal to the tourniquet while arterial inflow is unaffected. Low-load exercise at 20-30% of the individual’s one-repetition maximum then has similar muscle building effects as conventional strengthening techniques.
During high-intensity exercise, skeletal muscle’s demand for oxygen outstrips the supply. This results in accumulation of lactic acid and other metabolites, which stimulates the production of growth hormone and opens up intracellular signaling pathways, satellite cell (muscle cell precursor) activity, and fiber type recruitment patterns. Muscle hypertrophy and hyperplasia ensue. BFR training takes advantage of this normal physiological response to exercise; but with BFR, the effects of high-intensity training are only simulated. The tourniquet mechanically restricts outflow of blood and thereby causes pooling of low-oxygen-tension blood in the capillaries. The same physiological response of muscle hypertrophy and hyperplasia occurs.
One reason that BFR training was slow to catch on is that the original method required the use of a proprietary inflatable cuff. Ensuing studies have shown that a blood pressure cuff inflated anywhere between 50 and 150 mmHg or an elastic band applied with “moderate” tightness provides a similar effect.
BFR training not only affects the muscles that are located entirely distal to the cuff, it also affects those muscles under the cuff and even at least some muscles that are entirely proximal to the cuff. For instance, a cuff placed on the upper arm affects forearm muscles, biceps and triceps, and pectorals. Gluteal muscles are similarly enhanced by use of BFR on the thigh. Furthermore, BFR has been shown to prevent muscle atrophy even when applied without exercise.
The possible importance of applying BFR in rehabilitation settings is profound, and I will discuss some recent avenues of investigation, the unknowns of BFR optimal dosing, and possible deleterious side effects next month.