Trendsetter's gym selfie has brought BFR strap training, which comes from Japan and is based on a well-known rehabilitation method, back to the fore; But is it even suitable for everyone and do its benefits outweigh the drawbacks? This is not clearIn this day and age, sometimes all it takes to turn an obscure trend into a viral phenomenon is a selfie by the right star. And now it has happened again — this time thanks to Hailey Bieber, a serial trendsetter who has repeatedly proved she can turn almost any product into the internet’s latest obsession.After declaring some time ago that “Pilates is no longer in fashion,” Bieber posted a mirror selfie from the gym, showing herself in workout clothes with two black bands strapped tightly around her thighs. That was all it took to spark curiosity online, with users quickly trying to understand what was behind the mysterious fitness accessory.But as often happens, what looks like the latest invention from fitness influencers is actually an old idea that has been repackaged and given a small push by the right celebrity. The black bands are used in a training method called BFR, short for Blood Flow Restriction.It started with Hailey Bieber's gym selfie(Photo: Screenshot)Noam Klein, a physical therapist and fitness trainer at Clalit’s rehabilitation and physiotherapy institute in Hod Hasharon, in the Dan-Petah Tikva district, explains that the use of the bands is a familiar and accepted practice in rehabilitation.“These are bands that are placed on the arm or leg and are meant to restrict blood flow in a controlled way during exercise.“The pressure they apply mainly limits the return of venous blood from the limb, while arterial blood flow to it is preserved to a certain extent,” Klein explains. “As a result, a relative lack of oxygen is created in the muscle and exercise byproducts accumulate in it. The body responds to the effort as though it were high-intensity training. This makes it possible to strengthen the muscles using light weights, without placing stress on the joints and ligaments. That is why the method is especially suitable for patients after injuries or for those who cannot cope with high loads.”The roots of the method go back to Japan in the 1960s, when Dr. Yoshiaki Sato began developing it after an unusual experience: During a Buddhist ceremony, he sat for a prolonged period in a kneeling position and noticed that the “burning” sensation that developed in his leg muscles reminded him of the feeling after strength training.That experience gave rise to the question that would accompany him in the years that followed: Could muscles be made to work hard without lifting heavy weights, through temporary and controlled restriction of blood flow?Sato began conducting experiments and developing the method, which was given the name Kaatsu — a combination of the Japanese words “ka,” meaning addition, and “atsu,” meaning pressure. It was later adopted by researchers and professionals and gradually entered physical therapy clinics, rehabilitation centers and professional sports settings. Only later did it begin to make its way into gyms and into the routines of ordinary exercisers.Although many fitness trends that gain popularity on social media eventually turn out to be passing gimmicks, in the case of BFR there is also scientific literature supporting the method’s ability to improve muscle strength.A systematic review and meta-analysis published in 2022 in the International Journal of Exercise Science examined the effect of training that combines blood flow restriction on muscle strength. The researchers reviewed 327 articles and included 25 studies that met the criteria in the final analysis. The results pointed to a positive effect of BFR training on muscle strength. Subgroup analyses found no significant differences in results based on participants’ sex, the duration of the training program, training load or the type of cuff and pressure used.However, the findings should be qualified. The meta-analysis examined muscle strength only, so it cannot be used to directly infer an increase in muscle mass or to determine that BFR training is equivalent to high-load resistance training. The researchers also emphasized that further studies are needed to determine the most effective use protocols. In other words, the findings support the idea that the method may work, but they do not prove that every band, every level of pressure and every form of use will produce the same result.According to Klein, the practical advantage of the method is especially prominent, as noted, during periods when an injury, surgery or another limitation prevents training with normal loads — situations in which lack of movement can lead to a gradual loss of strength and muscle mass.“The studies and recommendations usually refer to patients or exercisers who want to preserve muscle mass and cannot place load on the body.”Using the bands also requires professional adjustment. The pressure is not supposed to be determined by feel alone, but according to the exerciser’s characteristics and condition.“You need a physical therapist or a professional who understands this, because the pressure has to be very specific and tailored to the person. Otherwise, it can cause damage. When the pressure is not personally adjusted, or the bands are not used properly, significant pain, tingling, temporary nerve damage, bruising or tissue damage can occur. In addition, pressure that is too high can also restrict arterial flow, contrary to the purpose of BFR. That is why it is important to adjust the pressure personally and use the method under the guidance of a professional who is familiar with the protocol,” Klein emphasizes.But even before that, it is worth knowing that the method is not suitable for everyone.“There are medical conditions that require professional assessment before treatment, to see whether it can be done at all,” she adds, “for example, patients with venous thrombosis, a history of blood diseases or uncontrolled blood pressure.”So are the bands here to stay? Not necessarily. At least outside the world of rehabilitation, Klein does not expect them to become a permanent part of the general public’s workout routine.“In the world of everyday exercisers, I don’t think we will see it too much, because in the end the central recommendation is to do regular strength training,” she concludes.Still, only time will probably tell.