I notice I am stronger than a year ago even though I almost got off medication then. For about 20 years, I have been unable to sprint because it invariably tore new flaps of cartilage in my knees each time I tried. I still ran slow, like 5k runs, up until now. However, the last few years, I find that if I am not extremely careful, the tendons that connect to the top front of my hip bones get injured (common injury for runners), even running slow. For the past 20 years, to avoid severe problems in my knees, I found it necessary to do daily isometrics for my interior quad (I don't really know what you call it, but the muscle on the inner side of the knee cap that opposes the tendon on the out side). But for the last 10 months, I have not done these exercises. And I have been sprinting without injury. And I have been sprinting and running 6 miles without the hip thing. And the tendon injuries that crippled both elbows for the last year have disappeared. The one elbow tear I got from repeatedly lifting my juicer to and from the top of the refridgerator every day in a weird way with one hand; the other elbow, I forget.
Bottom line: Best way to be strong and not break tendons and things is to Eat Real Food.