Rather than swinging the arm and racket together in a straight line to the ball, modern technique taps into what I call a "Snake" or "S" pattern that comes from twisting and releasing the arm. The butt cap of the racket starts out facing the left side of the fence with the wrist in a neutral position. The "forward swing" is really a big internal rotation of the shoulder and backwards rotation of the wrist followed by a pull forward. First the right shoulder internally rotates as the hand twists backwards. Now the butt cap of the racket faces the incoming ball (or even the right net post). This is followed by a pull forward. And finally the right shoulder release and externally rotates while the butt cap of the racket releases back into the body so it now faces the left fence again. The racket head gains rapid speed as it travels inside out.

Overall the racket ravels on a path that looks like the curve of a snake or of the letter "S". And it gets this motion from the stretching and elactity of the arm and shoulder and forearm and wrist. Twisting backwards, pulling and then releasing back into the ball.