There are a lot of weird training methods out there. Trapeze classes? Dragging sleds up hills? Backward running?! The weirdest exercise method I’ve ever heard of would have to be blood flow restriction training, also known as occlusion training or Kaatsu training. In short, blood flow restriction entails tying a tourniquet around your arm or leg while you lift weights.

It sounds weird. It sounds dangerous. It sounds dumber than dog yoga.

But amazingly, blood flow restriction training is both safe and effective. As far as I know, nobody has ever lost an arm or a leg doing it—and the lifting is arguably safer than traditional weightlifting. In fact, it might the single best methodology for gaining muscle while minimizing stress on your joints, which is why I often use it with clients who are elderly or recovering from joint injuries.

How Blood Flow Restriction Training Works

If you haven’t heard of blood flow restriction training before, you might be surprised to hear that it isn’t even remotely new. It was invented in Japan in 1966, where it was originally called Kaatsu training. The inventor, Dr. Yoshiaki Sato, came up with the idea after a Buddhist ceremony in which he has to remain kneeling for so long that he occluded the blood flow to his calves and he thought, “Hey, this feels just like the burn from doing calf raises.”

The training method he devised involved lifting light weights while wearing tourniquets or elastic bands around the limbs in order to restrict blood flow. This blood flow restriction causes blood to pool in the muscle, producing swelling and “the burn,” thus achieving high exercise intensities while lifting low weights.

How low? The weights used in occlusion training sessions are typically between 30 and 50 percent of the trainee’s one-rep maximum for that movement. By comparison, more typical weight training methods use intensities between 70 and 90 percent of one-rep maximum for compound movements, and 60–75 percent for isolation movements.

As for the method of wrapping, the cuffs used should be 2–4 inches (5–10 cm) wide. The exact width doesn’t matter very much, as long as the pressure is spread out enough that the wrap isn’t digging into your skin. What does matter is where and how tightly you wrap your limbs. The wraps should be placed around the top of the limb (upper thigh or upper arm) regardless of the exact exercise being performed. So even if you’re doing calf raises, you should wrap your thighs near where they meet the hip, not closer to the calves. I’ll explain why in a minute.

As for tightness, you want the wraps to be tight, but not as tight as possible. On a subjective scale from 1 to 10, the optimal tightness is about a seven for legs and a six for arms. With this amount of pressure, venous return is occluded, but arterial blood flow isn’t—that is, blood can get into the occluded limb as usual, but is restricted from leaving, causing the affected limb to swell.

By comparison, a medical tourniquet used to stop bleeding would be tight enough to stop arterial blood flow. This is why you’re still able to use your limbs while they’re occluded—nutrients are still being delivered to the limb. This is also why occlusion training is perfectly safe, at least for the 15–20 minutes that the bands are worn in studies.

Yeah, but How Effective Is Blood Flow Restriction Training?

Multiple studies have found that blood flow restriction training increases muscle growth in both occluded and non-occluded body parts. That is, wrapping your arms will boost growth in both the arms and chest, and wrapping the legs will boost growth in both the legs and glutes. This appears to be because the greater effort needed causes an increase in muscle activation across all involved muscles.

Many studies have compared the effects of blood flow restriction training with traditional high- and low-load resistance training. Blood flow restriction training consistently outperforms training with similarly low loads without blood flow restriction. However, traditional high-load training still produces significantly better strength gains, and seems to slightly edge out occlusion training for mass gains as well.

Multiple studies have shown that blood flow restriction training produces substantially less muscle damage than standard weight training. Crucially, this reduction in muscle tissue breakdown is not accompanied by a concomitant decrease in muscle protein synthesis. Muscle damage is not a necessary prerequisite for muscle growth, and it turns out that occlusion training is one of the best ways to get the growth without the muscle damage.

As for joint stress, studies have found that if you wear occlusion bands, the amount of joint stress you experience is just the same as if you lifted the same amount of weight without the bands. When it comes to joint stress, 50 pounds is 50 pounds.

Practical Guidelines

Based on the research, you shouldn’t use blood flow restriction training with the expectation that you’ll gain more muscle than you would with traditional strength training, and you definitely shouldn’t use it if your main goal is maximal strength. Blood flow restriction training is more likely to come in handy in the following situations:

• If you’re prone to joint injuries, either due to osteoarthritis or a previous injury, BFR lets you avoid joint stress.
• BFR lets you build strength and mass without sacrificing endurance.
• BFR does very little muscle damage, so you recover faster, making it useful for high-frequency training.
• Because it minimizes both muscle damage and injury risk, BFR is ideal for athletes preparing for important competitions.

How to Use Blood Flow Restriction

Use about half the weight you would normally use. Wrap your limbs near the top, just tightly enough to induce an extreme pump and burn during your sets. Keep them wrapped between sets, but not for more than four sets or 10 minutes. You should never feel light-headed; if you do, unwrap your limbs and wrap them more loosely the next time.

Blood flow restriction training can be brutal—your arms and legs will hurt from the intense pumps, but on the plus side they won’t continue to hurt the next day, at least after you’ve done it a few times. As you can see from the studies, this style of training is safe, effective, and an excellent choice for athletes who are worried about joint injuries or their ability to recover quickly from exercise.