Diet and nutrition for performance: WACE Physical Education Studies Unit 3
“Explain the role of carbohydrate, fat, protein, fluids and the timing of intake in fuelling performance and recovery”
Carbohydrate is the main fuel for moderate and high intensity exercise and is stored as glycogen. Fat fuels low intensity, long duration work. Protein builds and repairs muscle. Fluids maintain blood volume and temperature, and dehydration sharply impairs performance. Timing matters: athletes load carbohydrate before endurance events and refuel with carbohydrate and protein soon after to restore glycogen and repair muscle.
What this dot point is asking
WACE expects you to state the role of each macronutrient, explain hydration and the effects of dehydration, and describe how timing of intake supports performance and recovery. Application to a specific athlete and event earns the marks.
Carbohydrate
Carbohydrate is the body's main fuel for moderate to high intensity exercise. It is stored as glycogen in the muscles and liver and converted to glucose for energy. Because glycogen stores are limited, they can be depleted in prolonged or repeated high intensity exercise, which causes fatigue. A diet high in carbohydrate keeps glycogen stores full, supporting both training and competition.
Fat
Fat is a large energy store and the major fuel for low intensity, long duration activity, where there is enough time and oxygen to break it down. It supplies energy more slowly than carbohydrate, so it cannot fuel high intensity work alone. Trained endurance athletes become better at using fat, which spares glycogen and delays fatigue.
Protein
Protein's main role is to build and repair muscle tissue, including the repair and growth that follow training. It is not a major energy source under normal conditions, contributing significantly only in extreme endurance or when carbohydrate is exhausted. Adequate protein supports the adaptations of resistance and endurance training.
The simple rule is that as exercise intensity rises, the body relies more on carbohydrate, and as exercise lengthens at low intensity, it relies more on fat. This is why endurance athletes prioritise carbohydrate availability for race pace work while also training fat use for the long, easy kilometres. Match the fuel emphasis to the intensity and duration of the event in your answer.
Fluids and hydration
Water is essential for maintaining blood volume, transporting nutrients and oxygen, and regulating body temperature through sweating. During exercise, fluid is lost as sweat, and if it is not replaced the athlete becomes dehydrated. Dehydration reduces blood volume, which lowers the delivery of oxygen to muscles and impairs the removal of heat, so heart rate rises, body temperature climbs and performance falls. Even mild dehydration can measurably reduce endurance and concentration, so athletes drink before, during and after exercise.
Timing of intake
Before endurance events, athletes may carbohydrate load, increasing carbohydrate intake in the days beforehand to maximise glycogen stores so they last longer into the event. A pre-event meal rich in carbohydrate, eaten with enough time to digest, tops up the stores.
During prolonged events, taking in carbohydrate (such as sports drinks or gels) and fluid helps maintain blood glucose and hydration, delaying fatigue.
After exercise, consuming carbohydrate soon afterward restores glycogen most rapidly, while protein supports muscle repair, so a combined carbohydrate and protein intake speeds recovery for the next session.
Applying nutrition timing to an event
A marker wants the timing principles applied. Model answer: In the days before the marathon the runner carbohydrate loads to maximise muscle and liver glycogen, since glycogen depletion is a major cause of fatigue in long events. During the race the runner takes carbohydrate gels and fluid to maintain blood glucose and hydration, since dehydration would reduce blood volume and impair oxygen delivery. After finishing, the runner consumes carbohydrate soon afterward to rapidly restore glycogen, with some protein to repair the muscle damage from the prolonged effort. This timing supports the event itself and speeds recovery.
How this maps to the exam
Questions give an athlete or event and ask about fuel choice, hydration or timing. State which nutrient fuels the effort based on its intensity and duration, explain hydration and the cost of dehydration, and apply pre, during and post-event timing such as carbohydrate loading and post-exercise refuelling.
Students sometimes advise endurance athletes to eat large amounts of protein for energy. Protein's main role is muscle repair and growth, not fuelling endurance, which is powered mainly by carbohydrate and fat. For an endurance event, emphasise carbohydrate availability and hydration, and reserve protein for recovery and muscle repair rather than as a primary energy source.
Exam-style questions
Questions in the style of SCSA exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.
WACE 2021-style6 marksAn endurance athlete is preparing for a marathon. Explain the role of carbohydrate before, during and after the event, including the purpose of carbohydrate loading and the rationale for refuelling soon after finishing.Show worked answer →
A 6 mark explain answer needs carbohydrate's role across the three phases with reasoning.
- Before (carbohydrate loading)
- In the days before the event the athlete increases carbohydrate intake to maximise muscle and liver glycogen stores, the main fuel for prolonged aerobic work, delaying the point at which glycogen runs low.
- During
- Consuming carbohydrate (such as sports drinks or gels) during the race helps maintain blood glucose and spare remaining glycogen, sustaining the aerobic system and delaying fatigue.
- After (refuelling)
- Eating carbohydrate soon after finishing exploits the period when muscles take up and store glucose most rapidly, replenishing glycogen for recovery and the next session.
Markers reward glycogen loading to delay depletion, carbohydrate during to maintain glucose and spare glycogen, and prompt post-event refuelling for glycogen resynthesis.
WACE 2023-style4 marksExplain why adequate fluid intake is important for performance, and describe two consequences of dehydration on an athlete during prolonged exercise in the heat.Show worked answer →
A 4 mark answer needs the role of fluid plus two dehydration consequences.
- Role of fluid
- Fluid maintains blood volume and plasma so the heart can deliver oxygen and remove heat efficiently, and sweating relies on body water to cool the athlete by evaporation.
- Consequence 1: thermoregulation and cardiovascular strain
- Dehydration reduces blood volume, so heart rate rises and the athlete cannot dissipate heat as well, raising the risk of overheating.
- Consequence 2: performance decline
- Even small fluid losses reduce aerobic capacity, increase perceived effort and impair concentration and skill, so pace and decision making suffer.
Markers reward fluid's role in blood volume/cooling and two valid consequences (cardiovascular strain/overheating and reduced performance) with reasoning.