Which of the following are the three energy systems used during physical activity?

The correct choice identifies three specific energy systems that are critical in powering different types of physical activities. These are:

1. ATP-PC system: This system, also known as the phosphagen system, provides immediate energy through the breakdown of adenosine triphosphate (ATP) and phosphocreatine (PC) stored in the muscle. It is primarily used during short, high-intensity efforts, such as sprinting or heavy lifting, lasting about 10 seconds.

2. Anaerobic glycolysis: This energy system kicks in for activities lasting from about 10 seconds to 2 minutes, providing energy without the need for oxygen. It converts carbohydrates into glucose to produce ATP, resulting in the byproduct of lactic acid.

3. Aerobic system: This system operates when the intensity of exercise is lower, using oxygen to convert carbohydrates, fats, and sometimes proteins into ATP. It supports longer duration activities, such as running or cycling, typically lasting beyond 2 minutes.

Understanding these systems is essential for athletes and coaches as they determine the type of training and energy demands for various sports and exercises. This knowledge can help in designing training programs tailored to improve performance in specific events or physical activities.