Carbohydrates are the body's preferred source of energy during intense exercise because they can be broken down quickly and provide a rapid burst of energy.

Glycolysis is the first step in the breakdown of carbohydrates, where glucose is broken down into pyruvate, which is then further metabolized to produce energy.

Glucose is the simplest form of carbohydrate and is absorbed directly into the bloodstream, providing a quick source of energy.

Glycogen is the storage form of carbohydrates in the body and is found in the liver and muscles. It is broken down into glucose when the body needs energy.

Fats are a secondary source of energy during prolonged exercise and are broken down into fatty acids, which are then used for energy.

Lipolysis is the process by which fats are broken down into fatty acids and glycerol, which are then used for energy.

Unsaturated fats, particularly monounsaturated and polyunsaturated fats, are the preferred source of fat for energy during exercise.

Triglycerides are the storage form of fats in the body and are found in adipose tissue.

Proteins are used as a last resort for energy during prolonged exercise when carbohydrate and fat stores are depleted.

Proteolysis is the process by which proteins are broken down into amino acids, which can then be used for energy.

Alanine is the most commonly used amino acid for energy during exercise because it can be easily converted to glucose.

Muscle tissue is the storage form of proteins in the body.

The ATP-PC system is responsible for providing energy for short-duration, high-intensity activities by utilizing adenosine triphosphate (ATP) and phosphocreatine (PC).

The ATP-PC energy system lasts for approximately 0-10 seconds and is primarily used for activities such as sprinting and weightlifting.

The glycolytic system is responsible for providing energy for moderate-duration, high-intensity activities by breaking down carbohydrates into glucose, which is then converted to pyruvate.

The glycolytic energy system lasts for approximately 30-60 seconds and is primarily used for activities such as middle-distance running and cycling.