Understand the exercise-related function of food classes.

The idea

Each food class has a distinct role before, during and after exercise. Carbohydrates, stored as glycogen in liver and muscle, are the main fuel for high-intensity work and are broken down to glucose for glycolysis and the Krebs cycle. Fats provide fuel for lower-intensity, longer-duration activity through beta oxidation and spare glycogen. Proteins supply amino acids for repair and, in prolonged exercise, a small contribution to energy. Vitamins and minerals act as cofactors and electrolytes, supporting energy release and fluid balance, while water and fibre support transport and digestion. Link each class to the intensity and duration of the activity and to recovery.

What earns the marks

• Carbohydrates are the predominant fuel for high-intensity exercise and are stored as glycogen in muscle and liver.
• Fats are oxidised for energy at lower intensities and over longer durations, sparing glycogen stores.
• Proteins provide amino acids for muscle repair and adaptation, with a minor energy contribution during prolonged exercise.
• Vitamins and minerals act as cofactors in energy metabolism and as electrolytes that support hydration and muscle function.
• Water and dietary fibre support transport, temperature regulation and digestive health relevant to training and performance.

Common mistakes and how to put them right

• Treating protein as the main fuel for endurance exercise.

  Put it right: Carbohydrate and fat dominate, with protein making only a small contribution.

• Assuming fat cannot be used during exercise.

  Put it right: Fat oxidation is important at low to moderate intensities and spares glycogen.

• Describing vitamins as direct energy sources.

  Put it right: They act as cofactors that enable energy-releasing reactions.

• Ignoring timing: the function of a food class depends on when it is eaten relative to exercise, not only on what it contains.

Exam tips

• Name the food class, its stored or circulating form, and the exercise situation where it matters most.
• Use intensity and duration language, such as high-intensity short duration for carbohydrate and low-intensity long duration for fat.
• Link at least one food class to recovery as well as to performance.
• Avoid listing foods without stating their function, because the command word asks for function.