Originally Posted by TheLambsheadrep
so are you saying some of the shots are hit with a straight arm because incorrect take back/back swing technique?
Don't worry so much if your arm is 100% straight or 90%, that will depend on timing and shot you are trying to hit. Federer does not always hit with a straight arm. Most important thing is to load up the wrist and throw the racket so it brushes the ball upwards (spin) and drives it forward(pace), straight arm is a small detail you shouldn't so much worry about.
Just bend that elbow in and from there relax the arm, let it smoothly fall down and behind a bit and just throw the racket forward and up with the tension build up in the shoulder and the wrist from rotation of the torso for effortless power and spin.
Its a bit complicated to explain but once you feel that effortless groove you'll understand. A higher weight/SW racket helps.