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Fatigue and Recovery

Lactic acid, hydrogen ions and fatigue

  • 3 things to know
  • Component 1

Overview

Lactate and hydrogen ions, why lactate is not simply waste, blood lactate and OBLA, buffering, the breathing response, the 400 m runner's final 100 m, other waste products, DOMS and the trained endurance athlete.

What you need to know

Answer each one before you reveal it.

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Key term

What happens to lactic acid almost as soon as it forms in muscle?

Key term

How do hydrogen ions cause muscular fatigue?

Key term

Why is it misleading to call lactate simply a waste product?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What happens to lactic acid almost as soon as it forms in muscle?

    Model answer

    Lactic acid quickly dissociates into lactate and hydrogen ions (H⁺). The hydrogen ions, not the lactate, make the muscle more acidic.

  2. 2

    How do hydrogen ions cause muscular fatigue?

    Model answer

    Hydrogen ions lower the pH of the muscle. The acidity inhibits enzymes such as PFK and interferes with calcium binding to troponin, weakening contraction.

  3. 3

    Why is it misleading to call lactate simply a waste product?

    Model answer

    Lactate is a useful fuel as well as a marker of anaerobic work. The heart and slow twitch fibres can oxidise lactate, and the liver converts it back to glucose.

  4. 4

    What does a rising blood lactate concentration indicate?

    Model answer

    A rising blood lactate concentration shows lactate is being produced faster than it is removed. The glycolytic system is making a growing contribution.

  5. 5

    What is OBLA?

    Model answer

    OBLA, the onset of blood lactate accumulation, is the point where blood lactate starts to rise rapidly during exercise of increasing intensity. OBLA is usually placed at about 4 mmol/L.

  6. 6

    Why does working above OBLA lead to early fatigue?

    Model answer

    Above OBLA, lactate and hydrogen ions accumulate faster than they can be removed. Acidity rises steadily, so the performer must slow down within minutes.

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