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Diet, Nutrition and Supplements

Hydration, electrolytes and sports drinks

  • 3 things to know
  • Component 1

Overview

Electrolytes, hypotonic, isotonic and hypertonic drinks and when to use each, plain water in long events, hyponatraemia, hydrating before, during and after exercise, worked sweat loss and rehydration figures, and monitoring hydration.

What you need to know

Answer each one before you reveal it.

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Key term

A footballer's mass falls from 80.0 kg to 78.8 kg during a match, and 0.8 litres are drunk. Estimate the sweat lost.

Key term

What are electrolytes?

Key term

Why are electrolytes important during exercise?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What are electrolytes?

    Model answer

    Electrolytes are minerals that carry an electrical charge when dissolved in body fluids. Sodium, potassium, chloride, calcium and magnesium are examples.

  2. 2

    Why are electrolytes important during exercise?

    Model answer

    Electrolytes control fluid balance and allow nerve impulses and muscle contractions. Sodium also helps the body absorb and retain the fluid a performer drinks.

  3. 3

    What is a hypotonic drink?

    Model answer

    A hypotonic drink has a lower concentration of dissolved particles than the body's fluids. Water is absorbed rapidly, but little energy is provided.

  4. 4

    When is a hypotonic drink the best choice?

    Model answer

    A hypotonic drink suits a performer who needs rapid rehydration without extra energy. A jockey or a gymnast managing body weight is an example.

  5. 5

    What is an isotonic drink?

    Model answer

    An isotonic drink has a similar concentration of dissolved particles to body fluids, typically 6–8% carbohydrate. The drink replaces fluid and provides energy together.

  6. 6

    Why is an isotonic drink suited to a half-marathon runner?

    Model answer

    An isotonic drink supplies fluid, sodium and carbohydrate at once. The runner stays hydrated and fuelled without slowing fluid absorption.

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AThe training zone is 136 to 158 bpm.
BHeart rate reserve = (220 − 40) − 70 = 110 bpm.
CLower limit = (110 × 0.6) + 70 = 136 bpm.

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