Blood Flow Restriction Training: What Is It? How Does It Work?

Blood flow restriction training, also known as occlusion training or KAATSU, might sound like some sort of hardcore training method reserved only for meatheads and serious athletes, but that’s hardly the case.

In fact, it could be the perfect addition to a training plan for weekend warriors, a way to get older adults started with building strength and muscle, and a solution for rehabbing injuries faster than ever. 

I’ll explain what it is, how it works, what the latest research shows, and how to do blood flow restriction training.

What Is Blood Flow Restriction Training?

Blood Flow Restriction Training (BFR) is a style of weight training that uses higher reps and lighter loads while wearing a compression strap, tourniquet, or blood pressure cuff, on your upper arms or legs, depending on what you’re working.

Unlike traditional strength training, which requires you to lift at least 70% of your one-rep (1RM), BFR training increases muscle mass and strength using only 20-50% of your 1RM.

When I first came across that single statement, I was skeptical. However, I’ve learned to not let my skepticism keep me from trying something new.

I ordered a pair of BFR Bands and gave them a try. I was impressed with the results, and loved being able to give my joints a break from the constant grind of heavier weight training.

If there’s a “magic” in BFR, it comes from metabolic stress. 

The band, wrap, or cuff on your limb creates compression, occluding your veins while allowing for normal flow through your arteries.

The occlusion of your veins slows the return of low-oxygen, high-lactate blood flow from your arms or legs. The reduced flow also limits how quickly oxygen reaches your working muscle cells.

Like damming a flowing river, blood backs up, creating a “pump” in the muscle. This creates stress in your muscle cells, triggering numerous metabolic effects, leading to muscle and strength development.

If you want to skip over the technical details and get right to how to do BFR Training, jump to the bottom of this article.

For the sake of those who are skeptical, or even think this sounds scary, I’ll first go over the science behind BFR and the research supporting its use.

The Benefits Of Blood Flow Restriction Training

Blood flow restriction training increases strength and muscle mass at rates typically seen only by lifting heavy weight…without lifting heavy weight.

Traditional strength training programs use loads of at least 70% of an individual’s one rep max (1RM). Even young, fit, healthy athletes need a break from heavy training on occasion.

In addition, injuries, aging, surgery, and various diseases prevent people from using such heavy loads consistently.

Unfortunately, high-rep, lower-weight strength training doesn’t increase strength or muscle mass much…unless it’s done in combination with occlusion training.

When To Use Blood Flow Restriction Training

You can integrate BFR training into multiple different cases, such as:

• When traveling, and you don’t have access to all the equipment you’d normally use. You could do a BFR-only training session with the equipment typically found in a hotel.
• To rehab an injury, such as a torn biceps tendon or reconstructed ACL. Some research shows the effects can be transferred from one active limb to the other limb in cases of immobilization.
• To begin a strength training program as an older adult
• As a “deload” period to give your body a break, without losing strength or muscle mass
• During competition season to avoid impacting athletic performance, while still building muscle and strength
• To build or maintain strength and lean mass in people with degenerative diseases
• To slow the progression of cachexia or sarcopenia

Blood flow restriction can even slow the loss of muscle in an immobile limb without performing any exercise at all!

How Blood Flow Restriction Stimulates Muscle Growth

Occlusion training:

• causes a buildup of lactate and other metabolic byproducts
• limits oxygen delivery
• causes significant cellular swelling
• increases mechanical tension on the muscles

The altered cellular environment stimulates numerous changes to cells, genes, and proteins, many of which aren’t yet fully understood.

The following is just some of what helps create the gains in muscle and strength.

BFR suppresses myostatin expression. Myostatin is a protein that suppresses muscle growth. Without myostatin, we’d literally walk around looking like the incredible hulk.

You’ll never suppress myostatin enough to get that big, but suppressing a little does help build muscle. If you want to see what happens when an animal lacks myostatin, check out this short clip from National Geographic, about the Belgian Blue Bull.

BFR increases anabolic hormones. Growth hormone levels have been shown to rise up to four times over baseline from occlusion training. Standard strength training typically only doubles growth hormone. Testosterone levels may also rise.

BFR increases protein synthesis. Just as protein synthesis increases following a bout of high-load strength training, low-load resistance training, performed to failure and while using blood flow restriction also stimulates protein synthesis.

The mammalian target of rapamycin (mTOR) pathway is also activated, as are mRNA genes related to muscle growth.

Think about the potential with that last finding. If a well-trained athlete can improve his or her cardiovascular fitness and leg strength by walking on an incline using blood flow restriction, imagine the potential for older adults or people recovering from an injury!

One of the first recovery “steps” following ACL reconstruction is simply to walk. And in older people, the only thing they might be able to do in the beginning of a strength-building program is to walk. Walking while occluded increases leg strength and muscle mass.

A meta-analysis of occlusion training for musculoskeletal rehabilitation found that BFR produces better results than traditional training methods for those with ACL reconstruction, knee osteoarthritis, and adults with sarcopenia. 

Risks of Blood Flow Restriction Training

For the most part, there’s very few risks involved in occlusion training. However, anyone with a pre-existing condition should always consult with their physician.

In those with hypertension, blood pressure does rise a little more during BFR training than in traditional training. Interestingly, it also falls to lower levels than traditional training after it’s done.

Aside from this nuance, blood flow restriction training seems to provide no greater risks than standard exercise or resistance training would create. In some ways, it could be safer, since the loads used are lower than traditional strength training.

How To Do Blood Flow Restriction Training

The original form of occlusion training was called KAATSU, which was developed in 1966 in Japan. The KAATSU training technique requires a special certification and a digital cuff that costs several thousand dollars.

If you’re vying for the Olympics, where every fraction of a second and ounce of muscle mass makes a difference, finding an experienced KAATSU practitioner would probably be worth the investment.

Researchers often use blood pressure cuffs to ensure all study participants use a consistent pressure.

You don’t have to make things that complicated. Elastic wraps or bands work as well for most people.

The width of the band does make a difference, so if you think you’ll just go cheap and wrap a 4″ scarf around your limbs, don’t.

When the bands are too wide, they tend to occlude the arteries more than they should. Again, the goal is to occlude the veins, but not the arteries.

Band Placement

The bands should be placed as high as possible on your working limbs. That means you get them into your armpit when you train upper body (arms, back, chest).

For legs (quads, hamstrings, calves, glutes, etc.), get them up into your groin. The band should be just under the fold between your glutes and hamstrings on your backside.

Occlusion training has a positive effect on the muscles below and above the cuff, so putting them on your upper arm does affect chest or back strength and muscle growth, as well as your biceps, triceps, etc.

Keep your clothing to a minimum. For upper body days, a sleeveless shirt is perfect. 

The main thing is, you don’t want thick clothing under your wraps or bands as it makes the pressure less uniform, and you’ll end up with a chunk of clothing that bulks up and presses too hard under the cuff.

Band Tension

The purpose of the band is to occlude your veins without occluding your arteries. A tension of a 6 or 7 on a scale of 1-10 seems to work the best.

For you super-analytical types, I get that this is a “subjective” measure, but the research shows it’ll work just fine.

Time Under Compression

From a strength and conditioning standpoint, BFR works best as a way to finish your training session. In this way, BFR would be used for one or two exercises to finish a training session, keeping the bands or wraps on for the duration of all sets and rest periods.

As an example, you could do four supersets of leg extensions and leg curls, with 30 seconds rest between sets, while your thighs are occluded. Or, you might finish a push/pull training session with four sets of rows super-setted with chest press.

The sweet spot for BFR benefits seems to be 75 repetitions per muscle group per training session.

The possibilities are endless, but one thing is clear. More isn’t better.

You don’t need to do extra exercises, and you certainly don’t have to go heavy. But you do need to go to, or close to muscle failure with each set.

You’ll get all the benefits from BFR by using a single exercise for a specific body part. Older adults or those recovering from an injury may use BFR as the main form of training for a short period of time.

Muscle Failure

To produce the metabolic byproducts that stimulate strength gains, you have to reach momentary muscle failure, or get close to it. When you perform higher-rep sets, it takes considerable focus, and a drive to reach past the point of discomfort.

In my opinion, this will be the biggest challenge you’ll face with this type of training. You can’t stop when you feel like you’d done “enough.” You have to stop when you can’t possibly do anymore.

Often, pushing past the point of discomfort means doing another five to ten reps, not just one more like you’d do with heavier, traditional strength training.

Frequency

One of the many advantages of BFR is that it doesn’t cause the kind of muscle damage that traditional strength training does. It feels extreme right at the end of your session, but you recover quickly.

Doing BFR two to three times per week seems to have the greatest impact on hypertrophy.