A certain type of weight training keeps your muscles working non-stop, making them use more oxygen and possibly grow bigger because of changes inside your body.

Slow, low-effort weight training keeps your muscles working hard and starves them of oxygen more than fast, heavy lifting, which might help build muscle and strength just as well by stressing the muscles in a different way.

When doing slow, gentle weight training for your whole body, your muscles get just as tired and produce the same chemical buildup as fast, hard training—even though you're not lifting as heavy. This means your body is working hard in a different way to make the exercise effective.

When you exercise with less oxygen in your muscles—like training at high altitude or with special gear—you might build more muscle than when you train normally, because your muscles get more 'starved' for oxygen, which could trigger bigger growth.

A lighter workout style called LST can make your muscles produce as much lactic acid as a harder workout called HN, which might help build muscle size just as well, even though it's less intense.

Doing slow, controlled weight lifts with light weights can make your muscles use up more oxygen during the workout than doing the same lifts fast or lifting heavy weights—even if the heavy lifting feels harder.