When top powerlifters do a special type of weight training that restricts blood flow, it makes their slow-twitch muscle fibers grow more cell nuclei by 18%, but normal weight training doesn't do this.

Even though the muscles got bigger after the exercise, the number of special repair cells and nuclei inside the muscle fibers didn’t go up — meaning the growth happened without these typical building mechanisms.

When powerlifters do squats with restricted blood flow using lighter weights, it makes their slow-twitch muscle fibers grow bigger by 12%, while regular training doesn't change muscle fiber size.

When adults do light weight training with restricted blood flow, their slow-twitch muscles grow as much or more than their fast-twitch muscles, which is different from heavy weight training where fast-twitch muscles usually grow more.

When top powerlifters do a special type of exercise that limits blood flow to their muscles, their thigh muscle size grows almost 8% bigger—way more than the tiny growth from normal workouts.

When older people do strength training and their muscles grow a lot, the muscle cells add more nuclei—and those who grow the most gain about 32% more nuclei than those who don’t grow much.