Intense activities that last 30-45 seconds will predominantly rely on ______ for energy production.

Intense activities lasting 30-45 seconds primarily rely on anaerobic glycolysis for energy production. During this timeframe, the body needs a quick source of energy that can be provided without the need for oxygen, which is a characteristic of anaerobic metabolism. Anaerobic glycolysis efficiently breaks down glucose into pyruvate, allowing for the rapid production of ATP — the energy currency of cells — to support high-intensity efforts, such as sprinting or heavy lifting.

As the activity continues beyond this duration, the reliance may shift to other systems, but for activities specifically within that 30-45 second window, anaerobic glycolysis is crucial due to its ability to quickly generate ATP while maintaining higher exercise intensities. Consequently, this process relies on stored glycogen and can be sustained for a short duration before significant lactic acid buildup occurs, which can lead to fatigue.

In contrast, phosphagen (ATP-CP) is primarily utilized for extremely short bursts of high-intensity activity that last around 10 seconds or less, which makes it less applicable for activities extending to 30-45 seconds. Fat oxidation and aerobic glycolysis would come into play for longer-duration, lower-intensity activities where oxygen can be supplied and used efficiently, thereby making