After a tough workout, a protein fragment in your pee might show muscle damage just like a well-known blood test does — and they seem to go up together.

After a tough workout, men and women who regularly lift weights show similar levels of a muscle damage marker in their urine, suggesting it works just as well for tracking muscle soreness in both sexes.

After a tough workout, a protein found in your pee might show how much your muscles are struggling to recover — the more of it there is, the more your muscle power seems to drop.

After a tough workout, a certain protein in your pee doesn’t really match up with how sore you feel — it might be more about actual muscle damage than just feeling pain.

After a tough leg workout, a certain protein in pee goes up two days later — this might show how much muscle damage happened during exercise.

After really intense muscle workouts, healthy guys can have super high levels of a muscle enzyme in their blood—way above normal—peaking a few days later, which shows their muscles are breaking down a bit, but their kidneys are still fine.