I have been playing golf for about 8 years. A couple of years ago I noticed what looked like a tumor on the insides of both my knees. After inspecting I realized that it was muscle. I Had no clue how i got it. Later when I went to the golf course i started to pay attention to what my legs were doing during the swing. I became aware that there is a lot of torque and tension that builds up during the backswing as well as the follow through. In order to hit the ball 300+ yards like i do, I have to explosively release all of the tension in my right leg then stop the momentum with my left leg in order not to do a peroette. I am almost positive that playing golf, (hitting balls a the driving range), has made this muscle grow. Try it. swing hard and try to build up as much tension in your legs as possible. All sports require you to use your muscles. If played frequently and intensley, what other sports develop muscles that you wouldn’t normally think would be developed?