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At the 2012 summer Olympics in London, athletes tweeted about how they were cooling off in ice baths to aid recovery. In Rio 2016, ‘cupping therapy’ was hailed as the latest fitness trend, with competitors spotted sporting big red circular marks on their bodies. This year, it seems athletes at Tokyo 2020 have taken up blood flow restriction (BFR) to bolster their chances of winning.
The technique works much as the name suggests: bands are placed around a limb, restricting the flow of blood to muscles. If they’re worn during a training session, the muscles have to work harder because they’re being fed with less oxygen, which should mean that the wearer can work out at a lower intensity while stimulating the feeling of a much harder workout. If they’re worn after, the sudden rushes of blood when the bands are loosened are thought to prompt a response from the brain that speeds up the process of repairing damaged muscle fibres. Advocates are said to include American swimmer Michael Andrew – who, according to The New York Times, has been spotted wearing BFR bands in the practice pool – and marathon runner Galen Rupp.
“Blood flow restriction has an impressive ability to improve athletic performance and enhance recovery, very quickly, and very efficiently,” says BFR expert and founder of sportswear brand Hytro, Dr Warren Bradley. “BFR training has been around for the last two decades, but research has really accelerated in recent years. We’re seeing its use increasing in professional sports settings as a means to accelerate muscle growth, enhance recovery, and improve endurance.”
Team GB’s Rugby Sevens star Dan Norton says he’s seen the benefits first hand. “When we compete, it’s all about recovery and making sure my body is in top condition,” he explains. “I use BFR post sessions at the end of the day. Being able to sit on my bed, and relax and just reflect on the day and be able to recover – it’s an amazing tool to have that so easy and simple to use.”
But what does science say? Does restricting blood really help muscle grow, or is there some sort of placebo going on here? After all, the evidence for cupping is inconclusive at best – but that didn’t stop a wave of Olympians trying it out.
The research available is heartening. According to a paper from the Journal of Applied Physiology, published back in 2000, cutting off blood flow, then releasing it, can trigger the brain to speed up the normal process of healing and rebuilding damaged tissue. A more recent study from the Sports Medicine and Arthroscopy Review in 2019 shows that BFR can also be used as a rehab tool after surgical intervention. If a joint has been weakened, BFR allows the patient to lift relatively small weights, so as not to put the joint under undue strain, while still getting a significant muscular reward.
Yet despite the science of BFR for improving athletic performance, it has struggled to gain traction outside elite sports. To Bradley’s mind, it’s a lag that’s created by a lack of products currently available on the market. “You’re limited to expensive wired machinery used by medical practitioners one-on-one with athletes, inflatable cuffs that are time-consuming and difficult to set up and require supervision to perform safely, and cheap abrasive straps that are dangerous if applied incorrectly, often resulting in cuts and chafing,” he says.
“BFR is a great way to reduce physical impact and load while also providing enough stimulus to maintain and promote muscle mass growth,” explains sports scientist Esther Goldsmith.
“It’s ideal for people recovering from injury, but could be beneficial if you can’t access a gym or are feeling more fatigued at the end of a season. It also has positive clinical implications for older people and those with conditions such as osteoporosis.”
Are there any risks associated with limiting blood flow? Goldsmith says that while the results from the 2019 study suggest that, in a healthy patient population, low-intensity resistance exercise with BFR does not activate the coagulation system, not everyone falls under the definition of ‘healthy’.
“I would recommend that people get guidance in order to avoid any potential negative consequences (there have been reports of muscle soreness, numbness, dizziness and bruising) but also in order to use BFR effectively and achieve positive outcomes. There’s no point in doing it if you’re not going to do it properly,” she adds.