John is trying to gain more muscular strength to improve his performance in rock climbing. He currently runs 5 times a week at 65-85% of his max heart rate but has not seen any improvements. What fitness principle is he overlooking in his fitness plan?

Practice or pre-exercise theories of play pose the idea that a. play provides children with an opportunity to practice adult activities. b. play is necessary to reenergize human cognition. c. children have too much energy and play will rid them of that energy. d. children are the link between animals and human beings.