Notes · Physical EducationUK · A-Levels

Exercise Physiology

This chapter examines how diet and nutrition support and improve performance. It covers energy balance and the roles of the macronutrients, the micronutrients and hydration, the nutritional strategies performers use before, during and after competition, and the ergogenic aids - nutritional, physiological and pharmacological - that athletes use to gain an edge, with an honest weighing of their benefits and risks.

4 sections~14 min reading time3 competenciesLevel Foundation 1 · Standard 2 · Advanced 1

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Exam profile

AO1 · Describe energy balance, the macro- and micronutrients, hydration and the main ergogenic aidsAO2 · Apply nutritional strategies and ergogenic aids to named performers and eventsAO3 · Analyse and evaluate the benefits and risks of dietary and ergogenic strategies

Operators:describeexplainapplycalculateanalyseevaluate

basic level

AS-Level requires the components of a balanced diet, the roles of the macronutrients and the importance of hydration.

higher level

The full A-Level requires the detailed nutritional strategies (glycogen loading, timing) and the evaluation of nutritional, physiological and pharmacological ergogenic aids.

Depth

Text

Contents · 4 sections

Exercise Physiology

Energy balance and the macronutrients#

FoundationAQA 7582 3.2.2.1DfE GCE PE - diet and nutrition

Composition of a balanced diet for an active person

Fig. 1An active person's diet is dominated by carbohydrate to fuel and refill glycogen, with moderate fat and protein. Proportions are illustrative.

Energy balance is the relationship between the energy taken in as food and the energy expended through basal metabolism and activity. When intake equals expenditure, body mass is stable; a positive energy balance (intake greater than expenditure) leads to a gain in mass, and a negative energy balance (expenditure greater than intake) to a loss. Managing energy balance is the foundation of every performer's nutrition, whether a marathon runner needing a high intake to fuel training or a boxer making a weight category.

A balanced diet supplies the right amounts of the three macronutrients, along with the micronutrients, water and fibre. Carbohydrates are the body's main and most readily available fuel: they are stored as glycogen in the muscles and liver and are the preferred fuel for moderate-to-high-intensity exercise, so they should form the largest share of an active person's diet. They come as simple carbohydrates (quickly absorbed sugars, useful during and immediately after exercise) and complex carbohydrates (starches, giving a slower, more sustained energy release).

Fats are a concentrated energy store and the main fuel for low-intensity, long-duration exercise; they also insulate the body, protect organs and carry the fat-soluble vitamins. Because fat can only be broken down aerobically and yields energy more slowly than carbohydrate, its contribution rises as intensity falls and duration lengthens - the reverse of carbohydrate. Unsaturated fats are generally healthier than saturated fats, which in excess are linked to cardiovascular disease.

Proteins are the building blocks used for the growth and repair of tissue, including muscle, and to make enzymes and hormones; they are only used as an energy source in small amounts, mainly when carbohydrate and fat stores are low. Strength and power athletes need a somewhat higher protein intake to support the repair and growth of muscle after training. A performer's ideal balance of the three macronutrients therefore depends on their event: an endurance athlete emphasises carbohydrate to refill glycogen, a power athlete ensures sufficient protein for repair, and both must first meet their overall energy balance.

Worked example

Reading energy balance

A cyclist expends about 3200 kcal a day but consistently eats about 2600 kcal a day during a training block. State the type of energy balance and predict the effect, and suggest a correction if the aim is to maintain mass.

Compare intake and expenditure
Intake (2600 kcal) is less than expenditure (3200 kcal), a shortfall of about 600 kcal per day - a negative energy balance.
Predict the effect
A sustained negative energy balance leads to a loss of body mass and, if severe, to reduced training quality, fatigue and impaired recovery.
Correct it
To maintain mass the cyclist should increase intake by roughly 600 kcal a day, mainly as carbohydrate to refill muscle glycogen for training.

Result: The cyclist is in a negative energy balance of about 600 kcal per day and will lose mass; increasing carbohydrate intake to match expenditure restores balance.

Typical mistakes

Saying protein is a major energy fuel - it is mainly for growth and repair and used for energy only when other stores are low.
Assuming all athletes need the same diet - the macronutrient balance depends on the intensity and duration of the event.

Active revision

Compare the ideal macronutrient emphasis in the diets of a marathon runner and a weightlifter, and justify the difference in terms of their events.

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for physical education (Department for Education) · AQA A-level Physical Education 7582 specification (AQA)

Micronutrients and hydration#

StandardAQA 7582 3.2.2.1DfE GCE PE - micronutrients and hydration

Consequences of dehydration during exercise

Fig. 2Loss of body water reduces plasma volume, which raises heart rate and impairs thermoregulation and performance.

Micronutrients - vitamins and minerals - are needed only in tiny amounts but are essential for health and performance because they enable the body's chemical processes. Vitamins support functions such as energy release, immune defence and bone health: for example the B vitamins help release energy from food, vitamin C supports the immune system and the repair of connective tissue, and vitamin D (with calcium) supports bone health. A performer with an otherwise adequate, varied diet usually obtains enough vitamins without supplements.

Minerals have specific roles in performance. Calcium is essential for strong bones and for muscle contraction; iron is a component of haemoglobin (and myoglobin) and so is vital for oxygen transport, which is why iron-deficiency anaemia reduces endurance capacity; sodium and other electrolytes are needed for nerve transmission, muscle contraction and fluid balance. Female endurance athletes in particular need to ensure adequate iron and calcium. As with vitamins, a balanced diet normally supplies enough, and excessive supplementation can be harmful.

Water is not an energy source but is indispensable: it makes up a large fraction of the body, is the medium in which the blood transports oxygen and nutrients and removes waste, and is central to temperature regulation because sweating relies on the evaporation of water to lose heat. During exercise, especially in the heat, large volumes of water and electrolytes are lost as sweat, so maintaining hydration is essential to sustain blood volume, cardiac output and thermoregulation.

Dehydration - even a loss of body water of around 2% of body mass - measurably impairs performance. It reduces blood (plasma) volume, so the heart must work harder (cardiac drift, a rising heart rate at a fixed workload), it thickens the blood and reduces stroke volume, it impairs temperature regulation and raises the risk of heat illness, and it slows reaction time and concentration. Performers therefore hydrate before, during and after exercise, using water for shorter events and, for prolonged or intense exercise, sports drinks that also replace electrolytes and provide carbohydrate. Recognising the signs and consequences of dehydration and planning a hydration strategy is a standard applied question.

Worked example

Choosing a rehydration fluid

A triathlete will race for over two hours in warm conditions. Recommend a hydration strategy and justify the choice of fluid.

Identify the demand
The event is long and intense in the heat, so large volumes of water and electrolytes will be lost as sweat and glycogen will be depleted.
Before and during
Begin well hydrated and drink regularly during the race; because the event is prolonged, use an isotonic sports drink rather than water alone to replace electrolytes (especially sodium) and supply carbohydrate to spare glycogen.
After
Rehydrate afterwards with fluid and electrolytes to replace the deficit, alongside carbohydrate to refill glycogen.

Result: Start hydrated, drink an isotonic sports drink during the race to replace water, electrolytes and carbohydrate, and rehydrate fully afterwards - water alone would not maintain electrolyte balance over two hours.

Typical mistakes

Calling water a nutrient that provides energy - it provides no energy but is essential for transport and temperature regulation.
Ignoring electrolyte replacement - for prolonged, sweaty exercise, water alone may not maintain fluid balance; electrolytes are also lost.

Active revision

Explain how dehydration of about 2% of body mass would impair a footballer's performance in the second half of a match played in hot conditions.

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for physical education (Department for Education) · AQA A-level Physical Education 7582 specification (AQA)

Nutritional strategies for performance#

StandardAQA 7582 3.2.2.1DfE GCE PE - nutritional strategies

Muscle glycogen with and without carbohydrate loading

Fig. 3Tapering training while eating a high-carbohydrate diet raises muscle glycogen above its normal level, delaying depletion during a long race. Values are illustrative.

Because muscle and liver glycogen are the limiting fuel for endurance exercise - fatigue in long events often coincides with glycogen depletion ('hitting the wall') - a central strategy is to maximise the glycogen store before competition. Glycogen (carbohydrate) loading is a technique used by endurance athletes to raise muscle glycogen above its normal level. In a common modern protocol the athlete tapers training in the days before the event while eating a very high-carbohydrate diet, so the rested muscles 'supercompensate' and store extra glycogen, delaying the point of depletion during the race.

The timing of intake matters as much as the amount. Before exercise a carbohydrate-rich meal a few hours beforehand tops up glycogen without causing discomfort. During prolonged exercise, taking in carbohydrate (as drinks, gels or food) helps to maintain blood glucose and spare glycogen. After exercise there is a window in which the depleted muscle refills glycogen most rapidly, so consuming carbohydrate soon after finishing speeds recovery; adding protein supports the repair of muscle damaged by the session.

Protein timing is the parallel strategy for strength and power athletes. Resistance training damages muscle and stimulates its repair and growth, and consuming protein around training (including soon after) supplies the amino acids for that repair, supporting adaptation over time. This does not mean vast quantities are needed - a moderately raised total protein intake, sensibly distributed across the day and around sessions, is sufficient, and excess protein confers no extra benefit.

Hydration strategy completes the picture: performers aim to begin exercise well hydrated, to limit fluid loss during it, and to replace the deficit afterwards, using water or electrolyte drinks as the duration and conditions require. The key evaluative point is that nutritional strategies must be individualised and event-specific and, crucially, practised in training - trying an unfamiliar loading regime or an untested gel for the first time on competition day risks gastrointestinal upset and worse, not better, performance. Strong answers weigh the real benefits of these strategies against their practical demands and risks.

Worked example

Planning post-exercise nutrition

A rower finishes a hard 90-minute session that has depleted glycogen and caused some muscle damage. Recommend what they should consume soon afterwards and justify each element.

Carbohydrate
Consume carbohydrate soon after finishing to exploit the period of rapid glycogen resynthesis and refill depleted muscle and liver glycogen.
Protein
Add protein to supply amino acids for the repair and adaptation of the muscle damaged by the session.
Fluid and electrolytes
Rehydrate with fluid and electrolytes to replace sweat losses and restore plasma volume.

Result: A carbohydrate-and-protein feed with fluid and electrolytes soon after the session refills glycogen, supports repair and restores hydration - speeding recovery for the next session.

Typical mistakes

Recommending glycogen loading for a short, explosive event - it benefits prolonged endurance events where glycogen depletion limits performance.
Assuming more protein always means more muscle - a moderate, well-timed intake supports repair; excess gives no further benefit.

Active revision

A marathon runner asks how to fuel the three days before, and the morning of, a race. Recommend a nutritional strategy and justify it.

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for physical education (Department for Education) · AQA A-level Physical Education 7582 specification (AQA)

Ergogenic aids#

AdvancedAQA 7582 3.2.2.1DfE GCE PE - ergogenic aids

Classification of ergogenic aids

Fig. 4Ergogenic aids are grouped as nutritional, physiological and pharmacological; some are legal, others banned, and all must be judged for effectiveness and safety.

An ergogenic aid is anything that enhances performance, and the specification groups them into nutritional, physiological and pharmacological aids, each with benefits and risks that must be weighed. The overarching evaluation is that some aids are legal and effective, some legal but of limited or unproven benefit, and some illegal and dangerous, so a good answer never simply lists them but judges their legality, effectiveness and safety for the named performer and event.

Nutritional ergogenic aids include several with genuine, event-specific effects. Creatine supplementation increases the muscle's phosphocreatine store, benefiting short, explosive, repeated high-intensity efforts (sprints, weightlifting) by supporting the ATP-PC system; side effects can include water retention and, in some, gastrointestinal discomfort. Caffeine is a stimulant that can improve endurance and alertness and mobilise fat, but in high doses causes anxiety, a raised heart rate, dehydration and sleep disruption. Sodium bicarbonate acts as a buffer against the acidity produced by the glycolytic system, potentially aiding events of around one to several minutes, but commonly causes gastrointestinal upset. Nitrate (for example from beetroot) may improve the efficiency of oxygen use in endurance work.

Physiological aids alter the body's function or environment without a drug. Blood doping and, illegally, the hormone EPO increase the number of red blood cells and so the oxygen-carrying capacity, benefiting endurance - but both are banned and carry serious risks of thickened blood, clots, stroke and heart failure. Legal physiological methods include altitude training, which stimulates the natural production of red blood cells, and the use of cooling aids and recovery techniques. Pharmacological aids are drugs, mostly banned: anabolic steroids promote muscle growth and allow harder training but cause serious cardiovascular, hormonal, liver and psychological harm; beta blockers steady the heart rate and reduce tremor, aiding precision sports such as shooting and archery but banned in them; and stimulants raise alertness and mask fatigue but strain the heart and are addictive.

The key skill is evaluation, and it connects directly to the ethics of doping studied later. For each aid the performer and coach must ask three questions: is it legal (permitted by the World Anti-Doping Agency and the sport)? is it effective for this event? and is it safe? Legal nutritional aids such as creatine or caffeine may be justified for the right athlete when used carefully, whereas the pharmacological and blood-based aids are both illegal and hazardous, and their use is cheating that endangers health. A balanced conclusion recognises the real performance gains some aids offer while placing legality and long-term health above short-term advantage.

Worked example

Evaluating creatine for a sprinter

A 100 m sprinter is considering creatine supplementation. Evaluate its use against legality, effectiveness and safety.

Legality
Creatine is a legal nutritional supplement, permitted by the World Anti-Doping Agency - it is not a banned substance.
Effectiveness
It raises the muscle's phosphocreatine store, which supports the ATP-PC system, so it can benefit the explosive, short-duration effort of a 100 m sprint and repeated high-intensity training.
Safety
It is generally considered safe when used sensibly, though it can cause water retention (a small mass gain) and some gastrointestinal discomfort, and long-term high doses should be avoided.

Result: For a sprinter creatine is legal, effective for the ATP-PC-dominated event and generally safe in sensible use - a justifiable aid, unlike the banned pharmacological options.

Typical mistakes

Confusing creatine (nutritional, legal, aids explosive power) with anabolic steroids (pharmacological, illegal, muscle growth with serious harm).
Evaluating an aid only by whether it works, ignoring its legality and health risks.

Active revision

A 400 m runner and a pistol shooter each ask about an ergogenic aid. Recommend and evaluate one legal aid for each, considering effectiveness and safety.

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for physical education (Department for Education) · AQA A-level Physical Education 7582 specification (AQA)

References & sources

Sources

Department for Education

GCE AS and A level subject content for physical education

AQA

AQA A-level Physical Education 7582 specification

Exercise Physiology

4 sections~14 min reading time3 competenciesLevel Foundation 1 · Standard 2 · Advanced 1

Exercise Physiology

Key points

Reading energy balance

Key points

Choosing a rehydration fluid

Key points

Planning post-exercise nutrition

Key points

Evaluating creatine for a sprinter

Sources

Exercise Physiology

Key points

Reading energy balance

Key points

Choosing a rehydration fluid

Key points

Planning post-exercise nutrition

Key points

Evaluating creatine for a sprinter

Sources