Why is it that some people can jump rope for 20 minutes straight and not be able to run for that long and vice versa? Is it different muscle fibers? I thought both are forms of endurance training, so why would an athlete conditioned in one not be well conditioned for the other? I am trying to determine the best endurance tarining for doing long bouts of Forms in the martial arts. I'd like to hear Mr. Staley's opinion b/c I have been following his work lately but any answer is always welcome and appreciated.