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IB Sports, Exercise & Health Science: A.2 · Hydration and nutrition

Water balance, macronutrients, energy for exercise. 2 subtopics, 8 key terms.

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In this topic: A.2.1 · A.2.2

A.2.1Water balance and thermoregulation

Dehydration: A loss of body water that impairs function; even about 2% body mass loss can reduce performance.
Thermoregulation: Keeping core temperature around 37 °C.
Evaporation: Heat loss when sweat turns to vapour; the main cooling method during exercise.
Heat exhaustion / heat stroke: Heat illnesses; heat stroke (core temperature above about 40 °C) is a medical emergency.

Water is lost through sweat, breathing and urine; it is gained from drinks, food and metabolism. The kidneys regulate balance (with ADH).

The full notes, worked example and check questions for this subtopic are in the app.

Exam tip: Explain why humidity matters: high humidity reduces the evaporation of sweat, the body's main cooling method.

Macronutrients: Carbohydrates, fats and proteins: needed in large amounts and provide energy.
Glycogen: The stored form of glucose in muscles and liver.
Energy balance: Energy intake compared with energy expenditure.
Basal metabolic rate (BMR): Energy used at complete rest to keep the body alive.

Energy yield: carbohydrate about 17 kJ g⁻¹ (4 kcal), fat about 37 kJ g⁻¹ (9 kcal), protein about 17 kJ g⁻¹ (4 kcal).

The full notes, worked example and check questions for this subtopic are in the app.

Exam tip: Match the fuel to the intensity and duration: carbohydrate for high intensity, fat for long low-intensity exercise.