Which energy system is used for very short, maximal efforts lasting about 5-10 seconds?

• A. Glycolytic energy system
• B. Lipid oxidation system
• C. Aerobic energy system
• D. ATP-PC energy system

Answer: (D)

For very short, maximal efforts, the body relies on the phosphagen (ATP-PC) system. This energy pathway uses stored phosphocreatine to rapidly regenerate ATP in the muscle without needing oxygen, delivering power output at its peak for the first few seconds of activity. Because the PCr stores are limited, this system can sustain maximal effort only briefly—typically up to around 10 seconds—before it can’t keep up output and other systems begin to contribute.

As the duration extends past that initial window, glycolysis kicks in, providing more ATP from glucose and producing lactate, which supports sustained high-intensity effort but at a lower rate and with a faster fatigue pace. The aerobic system, which relies on oxygen, is slower to provide energy and supports longer, lower-intensity activity rather than maximal bursts. So for a 5–10 second maximal effort, the ATP-PC energy system is the dominant source.