Final answer:
The energy system used for running up a 100-yard hill as fast as possible primarily involves the ATP-CP system for immediate energy, transitioning to anaerobic glycolysis as the effort continues beyond 10 seconds, without relying on slower aerobic respiration.
Step-by-step explanation:
The energy system needed for running up a 100-yard hill as fast as possible is primarily the ATP-CP system and secondarily the anaerobic glycolysis/lactic acid system. The ATP-CP system provides immediate energy for high-intensity activities that last just seconds, which makes it suitable for the initial surge of energy required in such a sprint. However, because the ATP-CP system only supplies energy for about 8-10 seconds, and running up a hill might take slightly longer, anaerobic glycolysis will also contribute to energy production as the activity exceeds those 8-10 seconds but is typically less than 90 seconds. Consequently, this exercise involves anaerobic metabolism, as it is too intense and too short in duration to rely on the slow process of aerobic respiration.