Doing light weightlifting while restricting blood flow to the muscles can cause a big jump in special muscle repair cells, and this effect gets even bigger if you do it twice in a row.

This training makes your muscles grow and your strength go up — but not while you’re doing it. The best results show up weeks later, which means your body was under a lot of stress and needed time to recover.

At first, your muscles might actually get a little smaller from this kind of training, but after doing it again later, they grow bigger than before — the growth just takes time to show up.

Doing light weightlifting with a band that restricts blood flow for six weeks can make both slow and fast muscle fibers in older people grow bigger by about 20%, even without heavy lifting.

Both light and heavy lifting can boost the number of muscle repair cells in slow-twitch fibers, which might help muscles recover or adapt over time.

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.