Why can a physical activity of high-intensity and short duration be repeated after a brief recovery interval? (A) Other energy pathways are available for the immediate supply of phosphorus and creatine - HSC - SSCE Personal Development and Physical Education - Question 20 - 2003 - Paper 1

To understand why high-intensity activities can be repeated after a brief rest, we must consider energy systems in the body. The most important factor here is that of ATP (adenosine triphosphate) and its rapid resynthesis.

Among the options given:

• Option A discusses other energy pathways, but doesn't specifically address the key point about ATP regeneration.
• Option B correctly states that skeletal muscles have sufficient stores of ATP, thus minimizing the immediate need for phosphorus and creatine resynthesis.
• Option C focuses on oxygen availability, which, while important for longer activities, is not the primary factor in this brief recovery context.
• Option D indicates that the recombination process is rapid, which supports the ability to perform high-intensity activities in quick succession.

Given that the recombination of phosphorus and creatine is indeed rapid, this makes option D the most accurate reason for why such activities can be repeated efficiently after short rest periods.