In guys who lift weights a lot, certain chemicals in their urine that show stress on the body are closely linked to both worse performance and more training — meaning they might help tell when...

If guys who lift weights train too much — like a whole lot in a week — their bodies might get stressed in a way that could hurt their performance, and scientists can see this stress through certain markers in their body.

When guys who lift weights train too much, their body's natural antioxidants take a hit — they lose a lot of the good kind and build up more of the used-up kind, which might be why they start performing worse.

When guys who work out regularly do a 12-week weight training program, their body's uric acid goes up more and more as the program goes on, especially by the end — which might mean their bodies are under increasing stress from the workouts.