For how long does the ATP-PC system provide energy for muscle contraction?

The ATP-PC system, also known as the phosphagen system, provides a rapid source of energy for high-intensity activities lasting up to approximately 10 to 15 seconds. This energy system is the first to be utilized during short bursts of intense exercise, such as sprinting or lifting heavy weights. It primarily relies on stored adenosine triphosphate (ATP) and phosphocreatine (PC) in the muscle cells to regenerate ATP quickly.

When the muscles begin to contract, they draw from these stores to produce energy. As ATP and phosphocreatine are depleted, the capacity of the system diminishes rapidly, making it less effective beyond the 15-second mark. After this point, the body transitions to other energy systems, such as anaerobic glycolysis, to sustain muscle activity for longer periods.

When assessing the options based on the duration that the ATP-PC system can effectively supply energy, the correct choice aligns with the physiological understanding of energy systems in human physiology, particularly for activities of short duration and high intensity.