How does diet and nutrition affect performance, energy balance and recovery in sport?
The role of the macronutrients and micronutrients, hydration and energy balance, the importance of diet for different performers, and dietary manipulation and supplements such as creatine, sodium bicarbonate, caffeine and glycogen loading.
A focused answer to AQA A-Level PE exercise physiology on diet and nutrition, covering macronutrients and micronutrients, hydration, energy balance and the use of dietary supplements and ergogenic aids such as creatine, caffeine and glycogen loading.
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What this dot point is asking
AQA wants you to explain the role of the macronutrients and micronutrients, the importance of hydration and energy balance, how dietary needs differ between endurance and power athletes, and how performers use dietary manipulation and ergogenic aids such as creatine, sodium bicarbonate, caffeine and glycogen loading.
Macronutrients, micronutrients, hydration and energy balance
Hydration is vital: water maintains blood plasma volume, supports the transport of nutrients and helps thermoregulation through sweating. Dehydration of even 2 percent of body mass thickens (raises the viscosity of) the blood, reduces stroke volume so heart rate rises to compensate (cardiovascular drift), impairs sweating and temperature control, and measurably reduces both endurance and concentration, so athletes hydrate before, during and after exercise. The choice of drink matters: hypotonic drinks rehydrate fastest, isotonic drinks replace fluid plus carbohydrate and electrolytes during moderate exercise, and hypertonic drinks deliver more carbohydrate for energy but are absorbed more slowly, so they suit recovery rather than fluid replacement.
Dietary needs of different performers
An endurance athlete (such as a marathon runner) needs a high proportion of carbohydrate (often 60 percent or more of energy intake) to maintain the glycogen stores the aerobic system depends on, plus iron to support haemoglobin and oxygen transport. A power or strength athlete needs more protein to support muscle hypertrophy, growth and repair, alongside enough carbohydrate to fuel high-intensity training and creatine-rich foods to top up phosphocreatine. Timing also matters: a carbohydrate and protein intake within the recovery window after training speeds glycogen replenishment and muscle repair. Energy balance must match the workload, so a performer in heavy training needs a larger total energy intake to avoid an unintended deficit that would erode performance and recovery.
Dietary manipulation and ergogenic aids
Each aid has possible side effects: creatine can cause water retention and cramps, sodium bicarbonate can cause stomach discomfort, caffeine can cause dehydration and insomnia, and glycogen loading can cause water retention and bloating.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20196 marksEvaluate the use of creatine and sodium bicarbonate as ergogenic aids for a 100 m sprinter and a 400 m runner respectively.Show worked answer →
AO3 evaluation, balanced for both aids. Creatine for the sprinter: it supplements the muscle's phosphocreatine store, so the ATP-PC system can resynthesise ATP for longer, improving repeated explosive efforts and power output, with possible drawbacks of water retention, weight gain, bloating and cramps. Sodium bicarbonate for the 400 m runner: it acts as a buffer, raising blood pH and increasing the removal of hydrogen ions and lactate, which delays the onset of acidosis and fatigue in the heavily anaerobic 400 m, with drawbacks of nausea, vomiting and stomach cramps. A top-band answer reaches a justified judgement, matching each aid to the energy system the event relies on and weighing benefit against side effects. Reward the explicit link between aid, energy system and event demand.
AQA 20174 marksExplain the principle of glycogen loading and why it benefits a marathon runner but not a sprinter.Show worked answer →
AO1/AO2. Glycogen loading manipulates carbohydrate intake to maximise muscle and liver glycogen stores before a long endurance event. A common protocol depletes glycogen with hard training and low carbohydrate for several days, then tapers training while eating a high-carbohydrate diet for the final days, supercompensating the stores. It benefits a marathon runner because the aerobic system relies heavily on glycogen over the long duration, and a larger store delays glycogen depletion and the point of fatigue (hitting the wall). It does not help a sprinter because a sprint lasts only seconds and is fuelled by the ATP-PC system, not glycogen, so extra stores are irrelevant. Reward the link to the aerobic system and event duration.
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Sources & how we know this
- AQA A-level Physical Education (7582) specification — AQA (2016)