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Restricting blood flow makes muscles grow

Restricting blood flow makes muscles grow
Try this: restrict the blood supply to your legs at the groin and go run on a treadmill. Do two-minute 'sprints' of 100 metres, five times each training session. Do that five times a week for three weeks. According to Japanese research, you'll achieve unprecedented muscle growth.

The Japanese have been doing research for a while on training muscles at low level intensity with reduced blood supply to the muscles. They hope that under these conditions muscles grow faster and that 'training with restricted venous blood flow', as it is called, can help people who can't do ordinary strength training to build up strength. Old people, for example.

Strength training only 'works' with a load that is at least 65 percent of the 1RM. 1RM is the maximum amount of weight you can lift properly for only one repetition.

The researchers fitted their test subjects with a belt that restricted the blood supply to the legs, and then set them to walk on a treadmill. The photo above shows the set up. The control group walked without having their blood supply restricted.

The production of growth hormone rose considerably during and after the session. The concentration of cortisol (which wrecks muscles) remained low.

Restricting blood flow makes muscles grow

The researchers also measured free testosterone, IGF-1 and its binding proteins, and muscle damage markers. They found no effects.

The treadmill training did lead to a dramatic growth in muscle tissue, as the graph below shows. Kaatsu-walk = walking with restricted blood flow.

Restricting blood flow makes muscles grow

The photos below are from MRI scans. The upper photo shows the results of scan of the two legs of a test subject before the experiment started. The lower photo is of a scan of the legs of the same person at the end of the experiment. Quod erat demonstrandum, as they say in Asterix and Obelix.

Restricting blood flow makes muscles grow

Oh yes.

The test subjects got stronger by walking with belts tied around their upper thighs.

Restricting blood flow makes muscles grow

Exactly how the anabolic effect of training with restricted venous blood flow works, the researchers don't know. The theory they put forward is that restricting the blood flow to the muscle cells activates the glucose transporter GLUT4. But they don't have much evidence to support this theory.

J Appl Physiol. 2006 May;100(5):1460-6.

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