What is the primary energy system used during high-intensity activities lasting up to about 10 seconds?

The primary energy system utilized during high-intensity activities lasting up to about 10 seconds is the phosphagen system. This system relies on stored ATP (adenosine triphosphate) and creatine phosphate in the muscles to provide immediate energy for quick bursts of intense effort.

During high-intensity activities such as sprinting or weightlifting, the demand for energy is rapid, and the phosphagen system can supply energy almost instantaneously. It does not require oxygen and can regenerate ATP very quickly, making it ideal for activities that are short and intense.

Over longer durations of activity, or when the intensity decreases, other energy systems come into play, such as the lactic acid system or oxidative system, which rely on different biochemical pathways and substrates. However, for the brief and explosive efforts that last around 10 seconds, the phosphagen system is the most effective and predominant source of energy.