Jack Kramer & Three Minutes One routine we share comes from one of the greatest tennis players of all time. Jack Kramer copied one training drill from boxers. The goal of a boxer is to last fifteen three minute rounds. Kramer used to say that he was confident that he would never face an opponent who was fitter than him. He would skip rope at a rapid rate for three minutes and then do fast sit-ups for one minute. He repeated this four minute cycle fifteen times. By completing the intense sixty mi