The immediate (acute) responses to exercise, the short-term responses, and the long-term adaptations of the cardiovascular, respiratory and muscular systems to regular training.

What this dot point is asking

CCEA wants you to distinguish the body's immediate responses to a single bout of exercise from the long-term adaptations that build up over weeks and months of regular training. The immediate responses are temporary and reverse after exercise; the long-term adaptations are lasting structural and functional changes that improve fitness.

Immediate responses to a single bout of exercise

These responses all serve one goal: to deliver more oxygen and glucose to the muscles, remove carbon dioxide and lactate faster, and lose the extra heat being produced. They are driven by signals from the nervous and hormonal systems as exercise begins.

Short-term responses

In the minutes after exercise, the body shows short-term responses as it recovers. Heart rate and breathing rate stay raised above resting for a time to repay the oxygen debt, clear lactate and restore the body to its resting state. Muscle temperature stays elevated and the performer may feel fatigued. Delayed-onset muscle soreness, felt 24 to 72 hours later after unfamiliar or intense exercise, is also a short-term effect.

Long-term adaptations to training

The cardiovascular system adapts through cardiac hypertrophy (a larger, stronger heart, especially the left ventricle), which raises stroke volume and lowers resting heart rate (bradycardia), and through increased capillarisation, which improves oxygen delivery. Total blood and haemoglobin volume also rise. The respiratory system adapts with stronger respiratory muscles, a greater tidal volume and vital capacity, and more capillaries around the alveoli, improving gas exchange. The muscular system adapts with more and larger mitochondria and more myoglobin (improving aerobic energy production) in response to endurance training, and with muscle hypertrophy (larger fibres) and increased strength in response to resistance training. Together these raise maximal oxygen uptake, increase strength or endurance, and delay the onset of fatigue.

Examples in context

Example 1. The vascular shunt during a sprint. When a games player sprints, blood is redistributed by the vascular shunt: arterioles supplying the gut and non-essential organs constrict (vasoconstriction), while those supplying the working leg muscles widen (vasodilation). This diverts a much larger share of cardiac output to the muscles that need oxygen, an immediate response that reverses once the player stops. It shows how the body reprioritises blood flow the instant demand changes.

Example 2. Mitochondrial adaptation in a distance runner. After months of endurance training, a distance runner's muscle cells contain more and larger mitochondria and more myoglobin. Because mitochondria are the site of aerobic respiration, more of them lets the muscle produce more energy aerobically and rely less on anaerobic pathways, so lactate builds up more slowly and the runner can hold a faster pace for longer. This is a long-term muscular adaptation that directly raises endurance performance.

Try this

Q1. State three immediate responses of the body to exercise. [3 marks]

• Cue. Increased heart rate, increased breathing rate and tidal volume, the vascular shunt (increased body temperature and sweating also credit).

Q2. Explain how increased capillarisation improves endurance performance. [2 marks]

• Cue. More capillaries mean a greater surface area and more blood flow for gas exchange, so more oxygen reaches the muscles and fatigue is delayed.