Endurance, Fatigue and Fueling for Exercise

Endurance is a term widely used in sport and can mean many different things to many different people. In sports it refers to an athlete’s ability to sustain prolonged exercise for minutes, hours, or even days. Endurance requires the circulatory and respiratory systems to supply energy to the working muscles in order to support sustained physical activity.

What Causes Muscle Fatigue?
The reason athletes fatigue has to do with the available energy and the energy pathway the body uses for exercise at different intensities. During intense exercise, such as sprinting or lifting heavy weights, muscles rely on anaerobic metabolism, which can only produce a certain amount of energy at a time, unlike the aerobic metabolism system, which can continue to produce energy over hours.

Energy Pathways for Exercise - How Carbohydrate, Fat and Protein Fuels Exercise
Nutrients such as carbohydrate, fat, and protein contribute to the fuel supply needed by the body to perform exercise. These nutrients get converted to energy in the form of adenosine triphosphate or ATP. It is from the energy released by the breakdown of ATP that allows muscle cells to contract. However, each nutrient has unique properties that determine how it gets converted to ATP.