How do diet, hydration and ergogenic aids affect sporting performance?
The components of a balanced diet, the role of macronutrients and micronutrients in performance, hydration and dietary strategies, and the use and risks of ergogenic aids.
A focused WJEC A-Level PE answer on diet and nutrition for sport, covering macronutrients and micronutrients, hydration, dietary strategies such as carbohydrate loading, and the benefits and risks of ergogenic aids.
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What this dot point is asking
WJEC wants you to describe a balanced diet and the role of each nutrient in performance, explain hydration and dietary strategies such as carbohydrate loading, and evaluate the benefits and risks of legal and illegal ergogenic aids.
A balanced diet and the role of nutrients
- Carbohydrate is broken down to glucose and stored as glycogen in muscle and liver. It is the dominant fuel for the glycolytic and aerobic systems during moderate and high-intensity exercise, so a depleted store causes fatigue.
- Fat provides more than twice the energy per gram of carbohydrate but is used mainly during low-intensity, long-duration exercise, sparing glycogen.
- Protein supplies amino acids for muscle growth and repair after training; it is only a minor energy source.
- Vitamins and minerals support many processes: iron is needed to make haemoglobin (oxygen transport), and calcium and vitamin D for strong bones.
Hydration and dietary strategies
Water makes up most of the body and is lost through sweating during exercise. Dehydration reduces blood (plasma) volume, raises heart rate, impairs temperature regulation and reduces performance, so athletes drink before, during and after exercise. In prolonged events, sports drinks replace fluid, carbohydrate and electrolytes (such as sodium) lost in sweat.
Carbohydrate loading is a strategy for endurance athletes: glycogen is first depleted through training and a lower-carbohydrate intake, then a high-carbohydrate diet in the final days before competition supercompensates the glycogen stores above normal, delaying fatigue. Glycogen loading and timed pre-event meals are part of the same approach.
Ergogenic aids
- Creatine (legal). Increases the muscle's phosphocreatine store so the ATP-PC system resynthesises ATP for longer, benefiting explosive and repeated high-intensity efforts. Risks include water retention and possible cramping.
- Caffeine (legal in moderate amounts). Increases alertness and the use of fat as a fuel, sparing glycogen; risks include dehydration and, in very high doses, restriction in sport.
- Anabolic steroids (banned). Mimic testosterone to increase muscle mass and allow harder training, but cause serious harm (liver and heart damage, aggression) and lead to bans.
- EPO and blood doping (banned). Increase red blood cell count and so oxygen-carrying capacity, benefiting endurance, but thicken the blood and raise the risk of clots, stroke and heart attack.
Examples in context
Example 1. Iron-deficiency anaemia in endurance athletes. A distance runner with low iron makes less haemoglobin, reducing oxygen transport and aerobic performance. This shows micronutrients matter as much as macronutrients, a typical WJEC nutrition application.
Example 2. The cost of dehydration in a tournament. A tennis player who fails to replace fluid across a long match suffers a falling plasma volume, a rising heart rate and impaired concentration, illustrating why hydration strategy is part of preparation, not an afterthought.
Try this
Q1. Name the three macronutrients and state the main role of each in performance. [3 marks]
- Cue. Carbohydrate (main fuel, stored as glycogen); fat (energy for low-intensity, long-duration work); protein (growth and repair of muscle).
Q2. Explain how dehydration impairs sporting performance. [2 marks]
- Cue. It reduces blood (plasma) volume, raising heart rate and impairing temperature regulation, which reduces the delivery of oxygen and the ability to sustain effort.
Q3. Discuss one benefit and one risk of using creatine as an ergogenic aid. [4 marks]
- Cue. Benefit: more phosphocreatine, so the ATP-PC system resynthesises ATP for longer, aiding explosive repeated efforts. Risk: water retention and possible muscle cramps.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC 20184 marksExplain why carbohydrate is an important macronutrient for a games player and describe one dietary strategy that increases carbohydrate stores before competition.Show worked answer →
Carbohydrate is the body's main fuel for moderate and high-intensity exercise. It is stored as glycogen in the muscles and liver and broken down to provide ATP through the glycolytic and aerobic systems, so a games player relies heavily on it.
A larger glycogen store delays fatigue, allowing the player to maintain high-intensity efforts for longer.
Carbohydrate loading is a strategy in which the athlete depletes glycogen with training and then eats a high-carbohydrate diet in the days before competition, supercompensating the glycogen stores above normal.
Markers reward carbohydrate as the main fuel stored as glycogen, the link to delayed fatigue, and a correct description of carbohydrate loading.
WJEC 20206 marksDiscuss the use of two named ergogenic aids in sport, including a benefit and a risk of each.Show worked answer →
An ergogenic aid is a substance or method that enhances performance.
Creatine: it increases the muscle's phosphocreatine store, so the ATP-PC system can resynthesise ATP for longer, benefiting explosive, repeated high-intensity efforts. A risk is water retention and possible muscle cramps, and it is legal but must be sourced carefully.
Anabolic steroids: they mimic testosterone to increase muscle mass and allow harder training, benefiting power athletes. However, they are banned (illegal in sport) and carry serious health risks such as liver damage, heart problems and aggression, plus the consequence of a ban.
Other valid choices include blood doping or EPO (more red blood cells, so greater oxygen delivery, but increased blood viscosity and clot risk) and caffeine (raised alertness and fat use, but possible dehydration and over the limit it is restricted).
Markers reward naming two aids, a clear benefit linked to physiology for each, and a genuine risk (health or legality) for each.
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