during a windshield wiper forehand what is the role of the shoulder hinge if anything vs the elbow or forearm? is power derived from the hip rotation or shoulder rotation? Currently every time I drop my racket to get below the ball there's a straining feeling in my shoulder which has made me wonder if I am dropping the racket below the ball wrong? is it possible that bending the knees is the way to get below the ball? Thanks!!!!