DO REPS OF any exercise with a challenging weight (something beyond 65 percent of your max) and the muscles you’re working contract so tightly that they trap blood within them, preventing that blood from returning to your heart. This restriction of blood fatigues your muscles and leads to lactic acid buildup, which, eventually, pushes your body to “adapt” by building tougher, stronger muscles.
Do reps of any exercise with a challenging weight (something beyond 65 percent of your max weight) and the muscles you’re working contract so tightly that they trap blood within them, preventing that blood from returning to your heart. This restriction of blood fatigues your muscles and leads to lactic acid buildup, which, eventually, pushes your body to “adapt” by building tougher, stronger muscles.
It’s the mythic, muscle-building “pump,” and it relies on heavy weights. That’s why most strength workouts encourage you to lift as heavy as you can. But what if you could skip all those ultra-challenging loads and instead get superhero body benefits by tightening a few velcro bands around your thighs or upper arms?
That’s the promise of Blood Flow Restriction training. Once a niche method found only in the meatheadiest of bodybuilding gyms, it’s now being embraced by Hollywood A-listers, pro athletes, military personnel, and garage gym junkies alike. With everyone from Mark Wahlberg to Lakers star Dwight Howard on board, it’s the stuff of bro-science infomercials, except it’s actually backed by legitimate research -- and has more uses than muscle-building.
When done properly, with a device that properly monitors and maintains the pressure being put on your arteries and veins, and the blood flow within them, BFR can increase muscular strength, hypertrophy, and endurance with 30 percent of your max weights (much less than you’d use in a typical strength sesh), according to 2019 research published in Frontiers in Physiology. All you have to do is restrict blood flow to your legs or arms.
The History of BFR
THE PROCESS was first unlocked nearly a century ago -- and had nothing to do with building muscle. The first known study on BFR, published in the Journal of American Medicine in 1937, saw doctors use it to regenerate tissue and increase walking capacity in patients with lower-body circulation disorders.
Twenty-nine years later, Yoshiaki Sato, Ph.D., M.D., a Japanese weightlifter, sat in an hours-long Buddhist ceremony in the “Seiza” posture, thighs folded onto shins. When he stood, he felt his calves throbbing. Just 18, he theorized this pump was due to restricted blood flow and spent the next 40 years working to recreate the feeling by wrapping his muscles with bike tire tubes, ropes, and judo belts, with uneven success.
It wasn’t until he attached pneumatic bands to a digital control system that he could consistently and accurately monitor pressure and restrict blood flow. He dubbed his machine the Kaatsu (Japanese for “additional pressure”), and it remains one of just a handful of tools that effectively track blood flow. These tools cost serious coin (the Kaatsu runs $899, and the Delfi units used by NFL teams cost as much as $5,000).
Internet message boards claim you can DIY your own bands, skipping precise tracking, but experts caution against that approach. At worst, you’ll tighten the bands too much, risking permanent nerve and vascular damage. Leave them too loose and, all you’re really doing is lifting with too-light weights. “You’re probably not occluding to or maintaining the right pressure,” says Dr. Adam Anz of the Andrews Institute for Orthopaedics & Sports Medicine in Gulf Breeze, FL. “You have to maintain venous compression in order to get a systemic response.”
How Exactly Does Blood Flow Restriction Training Work?
KEEPING BLOOD from escaping back toward your heart makes BFR work. Deoxygenated blood is trapped in the muscle. New, oxygenated arterial blood traveling toward the restricted muscle stagnates and creates excessive pressure. Muscle cells overflow with blood, generating the “pump”. As oxygen dissipates, lactic acid pools within these muscles, triggering the same total-body fight-or-flight response you’d feel when doing, say, a max-effort squat set -- and driving a release of muscle-building proteins and hormones, including HGH and insulin-like growth factor (IGF-1). That means you get a “bloom” of those muscle-building metabolites all over your body, not just in the muscle you’re targeting with BFR.
But there’s a catch. While working with lighter weights spares your joints, it prevents ligaments and tendons from developing resilience, says Taylor Opitz, DPT, SCS, CSCS, also of the Andrews Institute, which is studying the cellular response to BFR. That limits your ability to use your newfound muscle.
“Beach muscles look great, but if you want your connective tissues to be able to handle a load,” says Opitz, “whether it’s a heavy squat or a heavy suitcase, you need to load them.”
This Isn't Just For Beach Muscle
BLOOD FLOW restriction training is actually at its best away from the big-arms crowd (see sidebar), when used by those coming back from injury, as Johnny Owens, MPT and owner of the BFR company Owens Recovery Science learned in 2011. While at the Center for the Intrepid, a Department of Defense rehab facility in San Antonio, Owens started using BFR to help blast injury victims build muscle without traditional weights. All showed dramatic increases in power and strength.
“We called some researchers looking into it in academic labs,” says Owens, then CFI’s chief of human performance optimization. “One of them point-blank said, ‘I don’t know what has taken you guys in rehab so long to accept this concept.’”
Now, pro teams like the New Orleans Saints use BFR regularly to rehab injured players. No, you can’t lift heavy weights with a torn ACL, or a cast on your arm. But you can still pick up light dumbbells, and that’s all Beau Lowery, Saints director of sports medicine, needs to help you retain strength. “Because of the increase in growth hormone and other hormone levels, even if a guy is in a cast or immobilized, we are able create muscle hypertrophy,” he says.
The gain is not without pain, however. Done effectively, Lowery says the pressure that builds up during BFR often leaves Saints linemen in tears, and at the Andrews Institute, Opitz says employees opted out of early BFR studies simply because the process was too painful. So before you test-drive this cutting-edge training method, best seek the guidance of a pro.
But there is a future for BFR, even if it’s not in your home gym.
The Best Ways to Use BFR
HEAVY WEIGHT training remains your best path to muscle, but if you can afford a BFR machine, supercharge your size by using BFR in these situations.
On lightweight training days
Once a week, ditch heavy weights. Pick 3 strength exercises. Start with a set of 30 reps for each motion, then do 3 sets of 15 reps each. Rest 30 seconds between sets.
On recovery days
Think you’ll be sore from today’s leg blast tomorrow? Lie down with cuffs tightly wrapped on your upper thighs and fully occlude blood flow for 5 minutes. Allow normal blood flow for 5 minutes; repeat 3 times.
As a finisher
Do 4 sets of a heavy bench press. Then grab light weights, attach the BFR cuffs, and do an isolated triceps move. Do 30 reps the first set, 15 in the other 3 sets. Enjoy the muscle--building burn. Do this at the end of your workout.
Other Cutting-Edge Uses of Blood Flow Restriction Training
BEYOND BICEPS, science now shows that blood-flow restriction may have other applications in health care and training. Watch for these four.
Platelet-rich-plasma treatment involves injecting your own platelets into your muscles and joints to speed healing. Two Andrews Institute studies have shown that BFR increases stem cells in your blood. Performing it prior to drawing blood for PRP can raise the levels of stem cells and platelets in a blood sample.
BFR may help combat sarcopenia, the age-related loss of muscle mass. According to a 2019 Sports Medicine review, older adults utilizing BFR achieved more muscle hypertrophy than those doing classic resistance training.
Post-concussion exercise has been shown to increase brain neuroplasticity, speeding recovery from traumatic brain injuries. BFR may allow patients to elevate their heart rates without worsening concussion symptoms. Duke University is testing the theory in clinical trials.
Research suggests that BFR training may be able to achieve an increase in blood-vessel elasticity as well as improve vascular function—key factors in managing cardiac disease and diabetes.
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