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.

If you lift light weights super slowly and hold the tension, your thighs get stronger and bigger after 12 weeks—but if you lift the same light weights at a normal pace, you won’t see much change.

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.

Lifting weights refills muscle energy slower than sprinting or HIIT, maybe because you don’t build up as much lactic acid and your muscles get more sore from stretching under load.

People who don’t lift weights regularly burn more sugar from their muscles during a workout than people who lift regularly.