Meanwhile, in Japan

Felt like writing something about exercise. After all, my education is in exercise science and not nutrition. This is about an exercise trend from Japan. It might be the next big thing in both muscle building and physical therapy and it may hurt like hell.

This is Kaatsu training!

Simply speaking Kaatsu training is occlusion training or training where a large part of the blood flow to and from the exercising muscles are restricted by a cuff. Its purpose is to increase muscle size without having to use high resistance and heavy loads.

Increasing muscle size is dependent on a variety of factors, but the important point is that muscles grow due to adaptation to stress. The larger the stress the stronger the effect (to a certain point) and it is the total amount of physiological stress that stimulates muscle hypertrophyIncreasing total stress can be achieved by for example increasing resistance, reducing break time, increasing number of sets and also as it appears, restricting blood flow.

Kaatsu training consists of performing low-intensity training while a relatively light and flexible cuff much like the ones used to measure blood pressure, is placed on the arms or legs usually close to the trunk. Inventor of Kaatsu training, Yoshiaki Sato, has worked with Kaatsu for more than 40 years and is still going strong.

Kaatsu may be an important tool in rehabilitation. Yoshiaki Sato, then at the Department of Ischemic Circulatory Physiology at The University of Tokyo describes his own experience with Kaatsu training: “…witnessing an older wheelchair-bound individual regain the use of his legs as well as another individual regaining sensation…”

Yoshiaki Sato in the 60’s while experimenting with Kaatsu




Kaatsu training does require some caution because blocking blood flow too much may be deleterious and cause thrombosis. Mr. Sato was himself hospitalized in the 1960’s after exercising with constricted blood flow and disregarding an increasing numbness in his legs. He experienced an episode of acute shortness of breath and was hospitalized with a pulmonary embolism. Sato later patented Kaatsu and made guidelines to reduce the risk of overdoing it like he himself did.


From Abe et al 2005
From the beginning it was clear that blood flow constriction combined with resistance exercise gave some exercise advantage even at levels as low as 20% of 1 repetition maximum (RM). Several studies have found increased muscle size at exercise intensities far lower than what may cause muscle growth under normal conditions.

In 2005 Sato with Takashi Abe and Charles F. Kearns demonstrated effects at even lower intensities. They made 18 young men walk on a treadmill 2 times a day, 6 days a week for 3 weeks. They did 5 sets of 2-minute bouts with treadmill speed at 50 m/min, with a 1-min rest between bouts. 9 of these men walked with a cuff round their thighs restricting blood flow.

The Kaatsu group experienced higher growth hormone levels during exercise and by day 4 their muscle-bone cross sectional area was significantly larger than that of the control group. By week 6 it had increased 6% in the Kaatsu group and nothing in the control group. In the Kaatsu group mid thigh quadriceps cross sectional area increased by 5.7% while hamstrings increased 7.6%. Leg press and leg curl 1RM strength increased by 7.4% and 8.3% respectively in the Kaatsu walk group, but not in the control-walk group. 

These results may be of great significance for elderly and frail people. Normally, if you want to achieve significant muscle size increases you must exercise at high intensities and often with large external loads (>65% of 1 repetition maximum). These training intensities however may not always be possible in the elderly. Here the scientists showed that walking in a relatively slow tempo can build muscles. This is great news, because muscle wasting is a serious problem especially in the older part of the population and may cause great disabilities and need for care.


Yoshiaki Sato in his 60s still experimenting with Kaatsu
When exercising limbs have a restricted blood flow the physiologic stress increases and muscles grow more than non restricted muscles. But recent data also suggest that non restricted muscles in multi joint exercises may benefit from Kaatsu. A recent pilot study examined the effects of low intensity bench press with restricted blood flow on chest muscle and triceps hypertrophy.

10 men were divided into low intensity bench press with or without occlusion. The exercise consisted of bench press at 30% of 1RM, four sets of a total 75 reps, twice daily, 6 days a week for 2 weeks. By the end of two weeks triceps and pectoralis muscle thickness increased 8% and 16% respectively in the Kaatsu group while the number were -1% and 2% in the control group. 1RM bench press also increased significantly in the Kaatsu group only.

I won’t go into the mechanisms here, but they are still poorly understood. I was once a part of an occlusion exercise experiment where I had 7 biopsies taken from my vastus lateralis muscles. I think one of the things the researchers were looking at was heat shock proteins. Growth hormone secretion has been shown to be increased with occlusion, some have suggested (mostly on the basis of animal studies) that myostatin and cortisol may be involved. Other hormones and growth factors have been measured, but no single mechanism has stood out yet.

Several studies on occlusion training have, in addition to hypertrophy and increased strength found increased oxygen uptake. A recent Korean study found that 2 weeks of occlusion walking increased maximal oxygen uptake in trained athletes. 

Although I am uncertain of the importance of Kaatsu in sports and regular recreational exercise (it is rather uncomfortable when you feel your legs pumping, turning red, and going numb) it is definitely an interesting method that might prove an important tool in physical therapy both for older people and athletes recovering from injuries.

So if you want to do it like they do it in Japan, just strap yourself in!