NCSF Sport Nutrition Specialist Certification (SNS) Practice Test 2026 – The All-in-One Resource to Master Your Certification!

The main source of energy for high-intensity exercise lasting less than a minute is creatine phosphate. During short bursts of intense activity, such as sprinting or heavy lifting, the body relies primarily on the phosphagen system, which utilizes creatine phosphate stored in the muscle cells. This system allows for rapid replenishment of ATP (adenosine triphosphate), the primary energy carrier in cells, enabling the muscles to perform at a high intensity without the delay that other metabolic pathways might involve.

Creatine phosphate provides an instantaneous source of energy, which is particularly crucial during the initial phases of high-intensity efforts when the demand for ATP exceeds what can be generated through other metabolic pathways. This is why it is the predominant energy source for activities lasting around 10 seconds to a minute, after which the body would start to use anaerobic glycolysis and aerobic metabolism more significantly.

In contrast, aerobic metabolism, though vital for longer-duration activities, is too slow to supply energy for rapid bursts required in high-intensity efforts. Fat oxidation is also not a suitable source during short, intense exercise because it is a slower process that predominantly supports endurance-type activities. Glycolysis does contribute to energy production during high-intensity exercise, but it primarily kicks