Blood Flow Restriction Training Isn't as Dangerous as It Sounds — but It's Not for Everyone

Even the most hardcore gym-goer will admit it's easy to be swayed by a shiny new training technique. Although they're aware that strength is built through long-term, consistent training, it's human nature to want a quick fix that will build muscle overnight, particularly when gains plateau.

Although blood flow restriction (BFR) training feels like a training loophole, it's no quick fix. If your progress has stalled, it can be a method worth trying. It can be beneficial for advanced lifters looking to improve or injured athletes looking to prevent muscle loss. But it's not right for everyone or every training session. Here's what you need to know.

Also known as occlusion training, blood flow restriction training is a lesser-known exercise technique used either for muscular rehabilitation or strength training. BFR involves wearing a pressure cuff or device to restrict blood flow to your working limb, says Sam Becourtney, physical therapist at Bespoke Treatments in New York City.

There are several theories as to the exact mechanism behind BFR, and a majority of research is still being done, Becourtney says. But it's generally understood that isolating or occluding a limb with a restriction cuff increases intracellular swelling. This process sends a variety of muscle-building signals out into the body, and all of this occurs with a lighter weight load than needed with standard strength training.

Specifically, the signals BFR produces help promote the anabolic (muscle-growing) process by increasing your body's growth hormone, according to a May 2015 study published in the Journal of Sports Medicine and Physical Fitness.

The best research in support of BFR is in a physical therapy setting. According to September 2017 research published in the International Journal of Exercise Science, occlusion training can be helpful for rehabbing injured muscles.

Lifting at a high load isn't feasible for post-surgery athletes, as they're generally under weight-bearing and/or range-of-motion restrictions meant to protect their healing tissues. But after a period of de-conditioning, light-load BFR can help strengthen muscles more quickly than exercising with a lighter load alone, according to a small July 2017 study published in the British Journal of Sports Medicine.

"We know the importance of regaining strength as early as possible [post-surgery], so BFR is an excellent option to help elicit similar strength gains without actually loading the repaired tissue, which would otherwise put you at risk for negatively impacting or ruining the repaired tissue," Becourtney says.

But this technique isn't only for injury recovery. For athletes whose sport revolves around increasing muscle mass, like bodybuilders, BFR can be a helpful hack. When compared to high-load training, low-load BFR seemed equally effective in increasing muscle mass, according to a February 2018 study published in Sports Medicine.

For standard strength training, you need to be lifting around 60 to 70 percent of your 1-rep max (the most weight you can lift once) to gain strength. But by restricting your blood flow to the working muscles, you're able to get the same results by lifting weights with only about 20 to 40 percent of your 1-rep max, Becourtney says.

Occlusion training hasn't been shown to cause further muscle damage, swelling or soreness, according to a March 2014 study published in the Scandinavian Journal of Medicine & Science in Sports. However, that doesn't mean it's the best or safest method for just anyone.

For one, patients who've undergone orthopedic surgery may be at higher risk of developing blood clots if BFR is implemented in their recovery protocol, according to a December 2018 study published in the Journal of Orthdopaedic and Sports Physiology.

BFR is also a relatively new method that hasn't undergone too much extensive research. While it may be safe strengthening technique for knee-related issues, for instance, that doesn't mean that it works safely for all injuries or patients, according to a June 2020 review published in the American Journal of Sports Medicine.

Some studies have reported patients experiencing adverse effects after BFR training, according to the above-mentioned review. Typically these effects include muscle pain or fatigue, which aren't too severe. But that doesn't mean everyone will experience the same side effects with the same severity. Again, there's no hard-and-fast rule.

Those who have recently undergone surgery should consult their doctor or physical therapist before trying this training method. Similarly, those who have prior medical conditions, like high blood pressure, deep vein thrombosis or cardiac disease (among others), should talk to their doctor before giving BFR a try, Becourtney says.

Also consider whether BFR aligns with your training goals. If you're working to increase muscle strength or size and still have the potential to increase the weight you're lifting, there's probably no need to resort to occlusion training, Becourtney says.

Generally, unless you're currently rehabilitating an injury which precludes you from lifting heavy loads or are a unique individual who is already squatting more than 500 pounds and may have back pain at greater loads, BFR is unlikely to be the most optimal next step.

No matter where you fall, consulting either a doctor or physical therapist before trying occlusion training is the safest way to go.

As previously stated, blood flow restriction is generally safe, but only if you set it up properly. You want to limit the restriction to 50 percent limb occlusion pressure for your upper body and 80 percent pressure for your lower body, Becourtney says.

"It's important to utilize a correct percentage of total limb occlusion pressure so as not to completely cut off blood supply to the limb and risk further damage," he says.

To guarantee you're restricting blood flow safely, he recommends using an FDA-approved piece of equipment with a restriction readout. These devices help adjust the amount of pressure on the cuff to ensure you're not restricting too much blood flow.

One downside, though, is that the safer and more accurate the tool, the more it costs. While you can buy BFR bands for as little as $30, these aren't necessarily accurate or safe. The most precise occlusion equipment includes an electronic machine, which reads off the amount of pressure being applied, Becourtney says. Generally, these devices are used in medical offices and can cost upwards of $1,000.

If these aren't in your budget, Becourtney recommends using FDA-approved BFR equipment, like Smart Tool USA Smart Cuffs ($349 for 2 cuffs). These are a little more affordable but still provide a pressure reading that you can monitor and adjust as you exercise.

Bear in mind that not all BFR devices are the same and most research is conducted using advanced, expensive units, which most people likely won't purchase for personal use. So, while consumer-available BFR devices may be able to re-create the same effect, there's no guarantee you'll see the same results as most research demonstrates.