If you wear tight bands around your arms or legs only when you're resting between weightlifting sets, your muscles will produce more lactic acid afterward than if you wear them while lifting or not at all—but that extra burn doesn’t make your muscles grow bigger or stronger.

If you're a young guy new to weightlifting and you use a blood pressure cuff to restrict blood flow while lifting, it doesn't matter whether you squeeze the cuff while you're pushing the weight up or while you're resting between sets—either way, you'll gain the same amount of strength and muscle.

If you use a tight band on your arm or leg while lifting heavy weights or resting between sets, it won’t make your muscles work harder—measured by electrical signals—when you’re a young guy who hasn’t trained before.

For people who exercise casually but aren’t trained, doing light weightlifting with blood flow restriction helps grow fast-twitch muscle fibers almost as much as lifting heavy weights — and after 6 weeks, the difference between the two isn’t big enough to matter.

Some people grow more muscle with regular heavy lifting, others grow just as much or more with heavy lifting plus blood flow restriction — there’s no one-size-fits-all answer.

When men who already lift weights do lots of reps with lighter weights, their muscles produce more lactic acid buildup than when they lift heavy weights for fewer reps, both right away and after two months of training.