During physical activity, the body makes changes to the blood to help the performer maintain their performance. (a) Explain how red blood cells help a perfo...

(a) How red blood cells help during prolonged exercise

Red blood cells contain a protein called haemoglobin, which has the ability to bind with oxygen molecules in the lungs. [1]

This allows oxygen to be transported from the lungs to the working muscles through the bloodstream. At the muscles, the oxygen is released and used in aerobic respiration to produce energy (ATP) for sustained muscle contraction. Without sufficient red blood cells and haemoglobin, the muscles would not receive enough oxygen and the performer would fatigue rapidly. [1]

(b) Long-term effect of regular exercise on the blood

Regular endurance training causes an increase in the number of red blood cells and haemoglobin concentration in the blood. [1]

This means the blood has a greater oxygen-carrying capacity. More oxygen can be delivered to the working muscles per unit of time, which improves aerobic endurance, allows the performer to sustain higher intensities for longer, and delays the onset of fatigue. This is a key adaptation that separates trained endurance athletes from untrained individuals. [1]

(c) Why iron is needed in the diet

Iron is an essential mineral required for the production of haemoglobin in red blood cells. [1] Without adequate dietary iron, the body cannot produce enough haemoglobin, reducing the blood's oxygen-carrying capacity. This can lead to iron-deficiency anaemia, characterised by tiredness, weakness, and poor exercise performance.