The more intense your workout, the more your body relies on carbohydrates to fuel it. Duration and intensity affect the degree to which carbohydrates and fat contribute to overall energy production. Review the following statements, and choose the ones that correctly describe the effect that intensity and duration have on glucose and glycogen use.

The more intense your workout, the more your body relies on carbohydrates to fuel it. Duration and intensity affect the degree to which carbohydrates and fat contribute to overall energy production. Both statements are true. However, the amount of carbohydrates in the diet, body composition and the muscle glycogen concentration are key components to define the use of carbohydrates or fat as energy.

Explanation:

Carbohydrates contributes to the first option for energy to the body and are the key fuel for the brain. During excercise, muscles use glucose from carbohydrate for fuel.

Carbohydrates can be used in anaerobic and oxidative pathways, that's why they support exercise over a range of intensities. Muscle and liver stores of glycogen provide the main source of energy in short and high intensity excercise, which need to be replaced post training.

During endurance exercise, glycogen can also break down fat into something the muscles can use for fuel. However, it is not so efficient as glucose. Protein can also be broken down and used as a last resort, but this stresses the kidneys and limits the body's ability to build and maintain muscle tissue.

Foods rich in carbohydrate are common options prior to exercise. They are generally well tolerated and preferred by athletes, in a way they are easily digested, in comparison to fat or protein foods.

For competitions: It is recommended a carbohydrate-rich diet consumed for 3 days prior to competition, accompanied by a decrease in training intensity. This results in increased muscle glycogen concentrations.