Even though your muscles feel just as sore and your blood shows similar signs of damage after doing leg exercises with your knee bent far back or only slightly bent, your muscles are actually weaker and harder to activate for longer after the deep bend version.

Just because your muscles aren’t sore or your blood doesn’t show damage markers doesn’t mean you’re not getting stronger—your body can adapt without those signs.

When healthy young men do a tough new workout that involves lowering weights slowly (like lowering a dumbbell), their muscles get sore and some blood markers go up, but within five days, everything goes back to normal—even if they’ve never done that workout before.

If you do a tough workout that stretches your muscles hard (like lowering weights slowly), then wait four weeks and do it again, your muscles won’t hurt as much or get as damaged the second time—they adapt and get tougher.

If you do hard eccentric exercises like lowering weights slowly once a week for 10 weeks, your muscles stop getting sore and damaged—even though the exercise is tough—because they get used to it.

When you do a new, super tough workout that stretches your muscles (like lowering weights slowly), your body gets sore and inflamed—but if you do it again every week for 10 weeks, your muscles adapt and don’t get as damaged. The key isn’t the type of movement, it’s that your body wasn’t used to it.