Blood flow restriction training (BFRT) has been a game changer in orthopaedic surgery rehabilitation. BFRT has been used since the 1960s, starting in Japan, where Dr. Yoshiaki Sato introduced it as Kaatsu training (‘training with added pressure’). It has become more popular (and more research-supported) in recent years, both in rehabilitation as well as strength and conditioning circles. Currently, it is the standard of care in rehabilitation of the patient who has undergone anterior cruciate ligament (ACL) reconstruction surgery. I use it on all ACL patients unless they have a contraindication (most don’t). The sports medicine physical therapists I work with are now experts in the technique.
There’s a lot of hype around BFRT, however, and it’s not super-approachable as a DIY modality. It involves placing a cuff on the upper thigh and/or upper arm to partially occlude blood flowing into the limb and dramatically reduce blood flowing out. The resulting build up of metabolites in the limb triggers a number of adaptations that can be harnessed for rehabilitation and performance. Since I was routinely prescribing it, I decided to gain some expertise as well. In 2021 I became certified by the University of Tennessee program in BFRT.
Exercising with the cuffs on is harder, as the muscles more quickly get fatigued. As a result, the muscle undergoes greater motor unit recruitment and ultimately, gets bigger (hypertrophy). Muscle protein synthesis is stimulated and the body produces more of its own growth hormone (a.k.a. the infamous human growth hormone, HGH) and insulin-like growth factor (IGF), anabolic hormones that stimulate muscle growth. Since this all happens with lower loads on the joints, it’s a natural fit for orthopaedic rehabilitation. During rehab, we often have the desire to fight muscle atrophy and build strength, coupled with the need to protect a graft, for example after ACL reconstruction. But BFRT can be used in healthy athletes to enhance performance.
Combined with low-load resistance exercise, BFRT can stimulate muscle growth as much as if you did high-load resistance exercise. High load remains more effective for increasing muscle strength, but BFRT plus low load is superior to low-load alone. I decided I needed to put the cuffs on myself. If I was prescribing them to my patients routinely, the technique should be good enough for me too. I still like to challenge myself with the high-load. However, if I’m injured or ill, or if I’ve already done some exercise that has been neuromuscularly fatiguing, BFRT plus low load has been a great alternative. The cuffs are also easy to travel with and thus ideal for when you don’t have access to weights, or are stuck with a lame hotel gym.
BFRT has been utilized with aerobic training as well. Most research protocols have studied cycling or walking. Researchers have found strength improvements of 7-27% and hypertrophy increases of 3-7%. Some studies have even shown improvement in maximal oxygen utilization (VO2 max), but that hasn’t translated into faster race times. This is an area I have not explored as much but am very interested to see what new data emerge. I’ve worn the cuffs on the stationary bike but haven’t made much of a protocol of it. BFRT walking could be a good twist on the post-prandial walk, though.
BFRT offers benefits even when not combined with exercise. It has been used in bedridden patients to prevent muscle atrophy. The muscle gains are much less pronounced than if you were to combine it with resistance training. However, the effects of immobilization can be devastating on muscle mass, so any way to offset this is welcome.
Two areas where I think more research will give us additional clarity are ischemic preconditioning (IPC) and recovery. IPC involves putting the cuffs on before the exercise. One recent study had participants warm up (5 minutes cycling at 50-60 watts, 5 minutes of dynamic stretching, 8 reps of bench press at 50% of target weight, 5 reps at 75% of target weight) followed by 5 minutes of BFRT. They then released the cuffs and did the bench press at the target weight. They compared them with controls who did the same protocol but simply rested while the experimental group did BFRT. Mean barbell velocity was increased by IPC and rate of perceived exertion (RPE) was decreased. Translation for performance? Unclear as yet, but worth looking into.
I recently attended the annual meeting of the American Orthopaedic Society for Sports Medicine. One of the speakers there mentioned that BFRT is being used as a post-game recovery tool in the NFL. This was something new to me. I checked with some other team physicians and trainers I know, including an NFL team physician, who reported that his team only uses BFRT for rehabilitation. One of my colleagues who works with a pro baseball team, however, confirmed that many of his pitchers use BFRT for passive recovery after games. Doing a literature search, I found a couple articles that did not support any benefit for BFRT for recovery. I did find one article which found an interesting benefit in using BFRT immediately after sprint training. They tested cyclists doing sprint workouts involving a 30 second max effort sprint. Within 15 seconds of completing the sprint, they had the participants lay on a table and inflate cuffs to 130 mm Hg for 2 minutes. This was repeated 4, 5, 6, or 7 times in week 1, 2, 3 or 4 of the four-week protocol. The control group did the same but without BFRT. The group using the BFRT during the recovery period showed an increase in VO2 Max of 4.5%! The control group didn’t change VO2 max at all. It was not only interesting that BFRT increased VO2 max, but also interesting that sprint training didn’t move the needle for their aerobic fitness. I suspect, however, that four to seven 30 second sprints is just not enough high intensity training to affect a trained cyclist.
Despite the apparent advantage of BFRT on oxygen utilization, when they tested the groups on a 15 km time trial, there was no difference. The researchers concluded that there are multiple factors that affect performance (especially mental factors) that are independent of VO2 max. The bottom line remains that there was no performance benefit in a time trial. But any endurance athlete can’t help but be enticed by a 4.5% increase in VO2 max. VO2 max is in many ways a vanity metric for endurance athletes. It puts your aerobic fitness into a number that can be compared to others, but doesn’t do jack to win you any races. Still, it does reflect fitness, and fitness is a component of performance.
What will BFRT show us next? I’m eager to see.