Carlos Alcaraz has taken his training to the next level with a controversial method that involves temporarily cutting off his own blood supply. The Spanish tennis star was spotted using black bands on his legs during a warm-up session at the ATP Finals in Turin, raising questions about whether he was nursing an injury.
In fact, the bands are a deliberate part of his training routine. Known as occlusion bands or blood flow restriction (BFR) bands, these devices restrict circulation to the limbs, helping athletes strengthen muscles and prepare their bodies for competition. Alcaraz first started using them in 2023 on his right arm before gradually incorporating them into both arms and, more recently, his legs during gym sessions and tournament preparations.
BFR bands were originally developed for injury rehabilitation. By limiting blood flow, they create a state of muscle hypoxia, making the muscle work harder even with lighter weights. For example, someone restricted to lifting 20 kilograms can simulate the effect of a 100-kilogram squat.
Over time, this technique moved from rehab settings into gyms and eventually into professional sports, particularly endurance and team sports.
Pedro L. Valenzuela, a researcher at Madrid’s 12 de Octubre Hospital, explained: “Badminton player Carolina Marin used them during recovery from a serious knee injury. From there, they spread to athletes in general, because blood restriction helps build muscle even with low loads.”
However, Alcaraz uses BFR bands at tournaments for a slightly different purpose known as ischemic preconditioning. The bands are applied with higher pressure, completely cutting off circulation for up to five minutes.
When removed, blood rushes back into the muscles, delivering more oxygen and improving mobility. The process also has an analgesic effect, reducing pain and potentially enhancing performance during matches.
Despite the benefits, the bands are not for everyone. Athletes with vascular issues risk thrombosis and many find the sensation unpleasant. “Some people don’t like them because they cause an unpleasant sensation,” Valenzuela added. “It’s what we call the nocebo effect. It’s like having your blood pressure taken for five minutes: your feet start to go numb, you feel a tingling sensation… Some people don’t want to use them.”
While the technique may look extreme, it is becoming increasingly common among elite athletes seeking small margins of advantage. For Alcaraz, the bands are just another tool in his arsenal, helping him stay at the top of the men’s game. And though the sensation is far from pleasant, the Spanish star clearly believes the temporary discomfort is worth the payoff on the court.
The 22-year-old has made a bright start at the ATP Finals. He beat Alex de Minaur 7-6, 6-2 in his opening match before beating Taylor Fritz 6-7, 7-5, 6-3. Up next he’s facing Lorenzo Musetti, where a win would clinch him top spot in the Jimmy Connors Group.
If he finishes top, he’ll face whoever comes second in a group consisting of Jannik Sinner, Alexander Zverev, Ben Shelton and Felix Auger-Aliassime in the last four.