How blood flow restriction training affects muscle fibers

When muscles grow from lifting weights, some types of muscle fibers might not get as strong or reliable as others, according to the numbers.

When adults lift heavy weights, their fast-twitch muscle fibers grow much more than their slow-twitch ones, based on several studies.

When people do light weight training with restricted blood flow very often (at least 5 days a week), their slow-twitch muscle fibers grow bigger faster. Some less frequent training also helps, but not as much.

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.

Scientists aren't sure yet if a newer type of lighter weight training works better than traditional heavy lifting for building a specific kind of muscle fiber in adults, because there haven't been enough direct comparisons and the few studies done so far have mixed results.