I’ll admit, the first time I heard about blood flow restriction (BFR) training, it sounded like a hack to me. BFR training promises that you can do relatively easy workouts and get the same results as if you crushed a hard workout at the gym. Too good to be true, right?
Don’t get me wrong, I’m all about less is more: Spend 30 minutes in the gym instead of an hour and a half. Go for a long walk instead of a long, grueling run in the black hole. Simplify your diet. However, I’ve seen fitness trends come and go, so I’m inherently skeptical until I see the evidence for myself.
Once I started to dig into the research, though, it became clear that BFR isn’t just a “get swole quick” gimmick. It’s a well-researched, validated training method used by physical therapists, rehabilitation specialists, and personal trainers to help patients and clients gain strength with minimal musculoskeletal stress. In some situations, it might be the best—or only—option to help someone maintain or gain muscle safely.
BFR was formalized as a training method in the 1970s and 80s by scientist Yoshiaki Sato, who called his technique KAATSU (“ka”=additional, “atsu”=pressure). Research interest has really picked up in the past decade, with a significant spike in the number of publications in the past three years.
I’m pretty sold on the potential benefits, but since you are restricting blood flow, you obviously want to be smart about trying it for yourself.
With BFR training, a band or cuff is worn tightly around the upper arm or leg. When done correctly, arterial blood flow is (mostly) unobstructed so blood can flow into the limb, but venous blood flow—blood pumping out of the limb—is impeded. BFR can be used in conjunction with resistance training, aerobic exercise like walking, or passively (no exercise). The majority of studies focus on resistance training.
This is the part that seems like a gimmick until you understand the underlying science. Normally when you’re resistance training to build muscle, the recommendation is to work at 60 to 80 percent of one-rep max (1RM). Your 1RM is the heaviest weight you could use to complete one repetition of an exercise—one biceps curl, one triceps extension, one deadlift. With BFR training, you usually lift weights equivalent to 20 to 30 percent of your 1RM.
A typical BFR workout comprises two to four sets of low-intensity, high-repetition exercises. For example, let’s say your 1RM for a squat is 150 pounds. In a regular high-intensity session, you might do three sets of eight 100-pound squats. Instead, with BFR training, you might do three sets of 20 or 30 squats with an empty 45-pound bar. The number of sets, repetitions, and rest intervals can be adjusted depending on one’s fitness and goals, just as with traditional training.1
Despite the much lower intensity, muscles respond as if they are under a heavy load. I say “lower intensity,” but believe me, the weight won’t feel light!2 If you’ve ever tried BFR, you know that you’ll break a sweat and breathe hard during a workout that should otherwise be easy. That’s because while you’re doing an “easy” workout, your muscles are screaming at your brain, “Hey, we’re working hard here!”
BFR is particularly useful in situations where people can’t lift heavy weights, or they don’t want to put extra wear and tear on their bodies, such as:
Essentially, BFR takes an otherwise easy workout and turns it into a max-effort workout, at least from your muscles’ perspective. The blood flow restriction causes changes to the cellular environment that mimic what happens during high-intensity exercise, leading to similar training adaptations.3
BFR works on two levels. Within the muscles, it creates metabolic stress.4 When you contract your muscles but blood flow is restricted, it produces a hypoxic (low oxygen) environment for the cells, and metabolites like lactic acid start to build up in the muscles. This signals to your muscles that they need to get stronger to deal with future stressors. Your brain also gets the memo that the muscles need help. The brain then initiates an autonomic nervous system response and a hormonal response—notably an increase in growth hormone, as well as insulin-like growth factors—that further promotes muscle protein synthesis.
Due to the metabolic stress they’re under, working muscles reach a point of failure much sooner than you’d otherwise expect. As slow-twitch muscle fibers start to drop out of the equation, fast-twitch fibers pick up the slack. As a result, you end up recruiting more of the muscle with less total effort.
Hundreds of studies have confirmed that low-intensity exercise with BFR is as effective or more effective for promoting muscle growth and strength gains compared to high- and low-intensity exercise without BFR. This holds true across sex, age, training status (trained versus untrained), and in healthy and patient populations. As a sampling:
In healthy young adults who weren’t currently strength training, six weeks of low-intensity resistance exercises conducted at 30 percent 1RM with blood flow restriction lead to significant improvements in strength, muscle activation, and torque.5 Their gains were similar to participants who engaged in traditional high-intensity exercise at 80 percent 1RM.
In another study, healthy young women did either traditional heavy resistance training or BRF at 30 percent 1RM.6 Results were similar across conditions, indicating that BRF training was just as effective for building muscle and strength and stimulating growth hormone release. The researchers also looked at gene expression for 29 genes known to be involved in muscle function and plasticity and found highly similar responses between the two conditions.
BFR training can help stave off the muscle atrophy that typically occurs after ACL surgery due to immobilization and disuse.7
Seven men with chronic hamstring or quadriceps weakness following traumatic injuries did knee extension and flexion exercises starting at or below 20 percent of their 1RM with BRF. After just two weeks, average power, total work, and torque all improved significantly, though there was significant variability between the men’s results.8
A 2017 meta-analysis of BFR in rehabilitation settings concluded that low-load restriction training is more effective and tolerable for patients than low-load training without BFR. It was not quite as effective as high-load training. Given that many folks can’t safely or comfortably lift heavier weights, low-intensity BFR training is a viable option for helping rehab patients recover strength and functional fitness.9
Walking while wearing cuffs on the legs improves strength and promotes muscle growth. 10 One study found that older adults who did BFR walks had greater muscle size and strength, along with better functional ability as measured by their ability to get up from and down into a sitting position.11
BFR training also has direct positive effects on skeletal health, increasing markers of bone formation in young men,12 older men,13, and postmenopausal women with osteopenia or osteoporosis.14
Restricting blood flow on one limb can lead to positive training adaptations in other parts of the body. In one study, participants wore a cuff on one leg only and performed resistance exercises at 30 percent 1RM. After six weeks of training, strength and muscle size, measured by leg girth, increased in both the cuffed and uncuffed leg.15 Numerous studies have found that chest muscles grow when participants perform low-weight chest presses while wearing arm cuffs, even though blood flow to the trunk isn’t impeded.16 The effect may not extend to aerobic exercise like walking, though.17
Low-intensity walking and cycling with BFR produce significantly greater improvements in aerobic capacity than low-intensity exercise without BFR.18
Whenever you’re blocking the flow of blood, there’s a potential for things to go wrong. Overall, the risk of adverse events is low, according to multiple studies and surveys of BFR users.19 20 Nevertheless, you should follow proper safety protocol to ensure that blood flow is not completely occluded, cuffs are not applied for too long, and exercises are done at an appropriate intensity.
That said, critics correctly point out that currently, there are no set standards for practitioners who wish to use BFR on themselves or with clients or patients. Experts disagree about whether narrower or wider bands are better and about how to determine the optimal pressure for a given individual. Some advocate for using one standard pressure for everyone, while others perform calculations based on the person’s systolic blood pressure, which measures arterial pressure. Still others use perceived tightness, aiming for a six or seven on a scale of one to ten.21
There are several reputable options for at-home BFR systems, including one designed and sold by Dr. Sato. These systems include cuffs that come with a machine or pump that allows you to control the pressure, and they will set you back several hundred dollars at least. You can also go online and find inexpensive bands you simply strap on. I can’t vouch for the safety of those cheaper, manual options.
Despite the apparently low risk of injury, if you’re new to BFR, it’s a good idea to ask a trainer or physical therapist who is trained in BFR techniques to show you the ropes. Potential negative side effects are numbness, dizziness, and delayed onset muscle soreness are possible.22 A handful of reports describe people developing rhabdomyolysis after BFR training.23 24 Rhabdomyolysis can occur whenever muscles are seriously overtaxed, which is why it’s important to lift lighter weights during BFR training sessions. Also, BFR is not advisable for certain populations without medical clearance. Check with your doctor before starting BFR if any of the following apply to you, or if you’re otherwise unsure:
You have a few different options when choosing blood flow restriction training bands and cuffs. Here are the pros and cons of each:
Think reusable tourniquet. BFR training bands are only about an inch or two wide, so they exert pressure on a small area of the muscle. These are risky to use – there’s simply too much room for error. Too little pressure, and they’re not worth much. Too tight, and you can give yourself nerve damage. I do not recommend these.
Compression bands are much wider than BFR training bands, which makes them a safer option. The downside is that there’s no way to measure how tight or loose you’re wrapping them. If you want consistent pressure for your workouts, opt for the occlusion training cuff, up next.
Think blood pressure cuff, complete with air pump and gauge. The cuffs are slightly more narrow than a blood pressure cuff, typically 3-4 inches wide. This drastically reduces your risk of nerve problems like the BFR training bands would cause. Since you can set your own pressure, occlusion training cuffs are probably the best option if you want consistency and accuracy. This is the option I would choose for myself.
The next step up is occlusion training cuffs that you control with your smartphone. People like these because the app can “remember” your settings for different muscle groups, and you get consistent pressure because you tell your phone where you want it to be. I’m an analog kind of guy, but I see the appeal.
Researchers are actively working on developing standardized approaches that will make BFR more accessible for the average person. Until then, do your own research and, as I said, seek out someone who knows what they’re doing to help you get started.
My prediction is that BFR will continue to gain popularity in both the fitness and medical spheres. It’s already aiding wounded warriors, professional and Olympic athletes, and everyday folks. The next big application might be BFR in space, allowing astronauts to maintain muscle mass in a low-gravity environment.25 For us earthbound folks, I’m guessing that the next big thing will be BFR for brain training.26
Overall, BFR shows tremendous promise, especially for helping people stay strong and active as they age and for recovering after injury or trauma. As to whether arm and leg cuffs will soon be the hottest accessories at your local gym… that remains to be seen. As effective as BFR is, old-school heavy lifting is here to stay. BFR training just doesn’t have the same brag factor as hoisting huge stacks of plates. Still, don’t be surprised if more and more people start sporting BFR bands during workouts.
I’m interested to hear from readers who have tried BFR training. What was your experience?
References
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