Response to Exercise

During exercise, your body's demand for energy increases. This lesson explains how the body responds to meet that demand, why anaerobic respiration kicks in during vigorous exercise, and how the body recovers afterwards. This is a frequently tested topic in the AQA GCSE Combined Science Trilogy specification (8464).

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Why Does the Body Need More Energy During Exercise?

When you exercise, your muscles contract more often and with greater force. This requires more energy, which is released from glucose by respiration. To maintain aerobic respiration, the muscles need more:

• Glucose — the fuel for respiration.
• Oxygen — required for aerobic respiration.

At the same time, more carbon dioxide (a waste product of respiration) is produced and must be removed.

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How the Body Responds

The body has several mechanisms to increase the delivery of oxygen and glucose to the muscles and to remove carbon dioxide more quickly:

1. Heart Rate Increases

• The heart beats faster (increased heart rate) to pump blood more quickly around the body.
• This delivers more oxygen and glucose to the muscles per unit time.
• It also removes CO₂ more rapidly.