“It’s a good supplement for training; it’s not all of your training,” Arent said. “It provides physiological stimulus when other things might be limited.”
Sato said he accidentally discovered the benefits of blood flow restriction more than 50 years ago, during a Buddhist ceremony in a Japanese temple that required him to sit on the floor in the seiza position — bent knees with his heels under his rear end — for long periods. His calves and toes began to tingle, and he could no longer stand the pain after 45 minutes. When he stood, he saw his calves pump up with blood, and his legs felt as they did during a workout.
Sato thought perhaps there might be some connection between cutting off blood flow to muscles and training them. He began tying karate belts and later bicycle inner tubes around his legs and performed a series of experiments, tracking how much the circumference of his thighs and calves would grow even when he performed fewer repetitions.
In 1973, Sato broke his ankle while skiing and restricted blood flow to the area during rehabilitation, letting it rush in periodically. A recovery that doctors told him might take four months took a little more than one.
“Pressure on, pressure off,” he said. “The benefits for both training and recovery was understood.”
For someone like Andrew, who swims thousands of yards every day, or Rupp, whose regimen includes more than 100 miles each week plus weight training and core work, or Noah Syndergaard, the pitcher for the Mets, or Mikaela Shiffrin, the champion skier, or any of the other top athletes who have started incorporating blood flow restriction, the technique allows them to reduce the likelihood of a repetitive stress injury and speed up recovery time.
For Andrew, the most important part of the technique may be how strongly he believes it works. As every sports scientist knows, placebos can often be as strong as any drug.
“I did something like 18 races in seven days at the trials, and I felt fresh,” Andrew said. “I’m sure it was because I was so disciplined with the recovery. I used it all the time.”