What is the immediate source of energy for high-intensity activities lasting less than 20 seconds?

The immediate source of energy for high-intensity activities lasting less than 20 seconds is anaerobic alactic metabolism. This type of energy system provides a rapid supply of energy through the breakdown of stored ATP and creatine phosphate (CP) in the muscles, allowing for explosive movements such as sprinting or jumping.

During activities that last a very short duration but require maximum effort, the body relies on this anaerobic pathway because it can quickly regenerate ATP without the use of oxygen. Since the exercises are brief, it does not involve lactic acid production, which occurs in longer-duration high-intensity efforts.

Other energy systems, such as aerobic metabolism, involve oxidative processes that take longer to activate and are not suitable for immediate, short bursts of energy. Fat oxidation, which primarily serves endurance activities, also takes longer to mobilize and is not the source for quick, explosive efforts. Glycolysis, while it does provide energy during higher intensity exercise, typically activates more fully in efforts lasting longer than 20 seconds and leads to lactic acid formation in high-intensity situations.