Weightlifting as a hobby

I’ve been very invested in weightlifting/powerlifting since 10th grade so I did that for about 8-9 hours a week. I was wondering if I should put that as an activity?

Absolutely.

Thanks, what should I put for the description? I put “Became stronger” but I think that comes off as sarcastic

I don’t think that would come off as sarcastic. Becoming stronger is a laudable goal! If you wrote your own workouts, you might incorporate that. Something like “Developed intensive powerlifting exercise program for myself with the goal of becoming stronger and more agile. Ran three days a week for 2 miles each day and weightlifted every day for an hour.”