What Is Kaatsu?

A fairly new method of building muscle from Japan, referred to by the Japanese acronym KAATSU, involves restricting blood flow to the muscles being worked. Translated as "low intensity vascular occlusion training," KAATSU was created by a physician and professor at the University of Tokyo, who studied the practice for nearly four decades before patenting the process and promoting it to the public. Though some question the results, at least one study shows that just as much muscle mass can be gained through KAATSU than non-KAATSU workouts with more weight resistance.

UT professor Yoshiaki Sato was credited with the patent for KAATSU in 1996. The process, according to the KAATSU International University, leads to the capillaries becoming filled with pooled blood in the areas where resistance is being applied. The practice is considered an intriguing advancement for those with reduced range of motion or weak cardiovascular health.

When working the biceps, for instance, a belt similar to that used for a blood pressure test is applied just above the biceps at the shoulder. Bicep curls are then executed as normal, with the belt providing an added supply of pooled blood. For working the triceps on the back of the upper arm, the belt would be placed in the same place. Exercises involving this partial occlusion are largely confined to the extremities; however, a belt wrapped around the midsection, just above the abdomen, is a way of adding partial occlusion to an exercise like sit-ups. Wrapping a belt around the neck, however, should never be attempted.

According to a study published by the American College of Sports Medicine in 2007, this form of partial occlusion created just as much fatigue in test subjects than exercises with more weight resistance that did not use blood-flow restriction. The researches also urged further research to ensure the safety of the practice. KAATSU International University maintains that when utilized as prescribed, the practice is safe and effective for stimulating added muscular growth.

Without blood-flow resistance, fitness trainers frequently recommend three or more sets of six to 12 repetitions per set — the weight set at about 70 percent of that person's one-repetition maximum. With partial occlusion, however, the resistance should be low, between 20 and 50 percent of the one-repetition maximum. Though it was long thought that such low weight would not be sufficient for hypertrophy, or breakdown, of muscles — a needed precursor to muscle-building — KAATSU researchers have shown regular increases in strength and mass with the method.