Sort of the opposite of a foam roller or massage, the therapy helps break up and deliver blood to overworked tissues.
"Think of us as an Indy Car pit crew, looking at the structure and alignment of the vehicle to see if there is any kind of drag or anything," chiropractor Kevin Rindal who worked with USA Swimming in 2016 told ESPN back then.
"And if you think of how close these racers are, a little bit of restriction adds up in each stroke and can prevent a full reach. It's basically the fine-tuning of the tissue."
It's different from another technique popular among this year's Olympians: blood flow restriction, in which athletes use bands to limit the blood to their muscles during training to stimulate muscle growth and to make racing without the bands feel easy by comparison.