Sigh, at this age, metabolism is slow and recovery is slow. You should take good care of it.

You can do it on your back or sitting. Straighten your legs, keep your knees still, and exert strength on your thigh muscles. You can see this with the naked eye, or you can't push the patella with your hands. This is success. Push hard for 5 seconds, relax for 3 seconds, and do it continuously for 10 minutes, which is about one day 1 time, 1 time.