Immediate (Short-Term) Effects of Exercise
When you begin exercising, your body responds immediately to meet the increased demand for energy and oxygen. These changes reverse when exercise stops.
Cardiovascular Responses
| Response | Explanation |
|---|
| Heart rate increases | The heart beats faster to pump more oxygenated blood to working muscles. HR can rise from ~70 bpm at rest to 180+ bpm during intense exercise. |
| Stroke volume increases | Each beat pumps more blood (from ~70 ml to ~120 ml or more). |
| Cardiac output increases | Q = HR × SV, so both rising together dramatically increase cardiac output. |
| Blood pressure rises | Systolic pressure increases because the heart pumps more forcefully. |
| Vascular shunting | Blood is redistributed from inactive organs (e.g. digestive system) to active muscles and the skin via vasodilation and vasoconstriction. |
Respiratory Responses
| Response | Explanation |
|---|
| Breathing rate increases | From ~15 breaths/min to 40–60 breaths/min to take in more oxygen and expel more CO₂. |
| Tidal volume increases | Deeper breaths bring in more air per breath. |
| Minute ventilation increases | MV = BR × TV — both increase, so minute ventilation rises significantly. |
| Oxygen debt (EPOC) | After intense anaerobic exercise, the body needs extra O₂ to remove lactic acid and restore energy stores. |
Muscular Responses
- Increased muscle temperature — muscles warm up, improving elasticity and reducing injury risk.
- Muscle fatigue — prolonged or intense exercise causes muscles to tire, reducing force output.
- Lactic acid accumulation — during anaerobic exercise, lactic acid builds up, causing a burning sensation and eventually forcing the performer to slow down or stop.
- Micro-tears in muscle fibres — occur during intense or unfamiliar exercise (this is what causes delayed onset muscle soreness, or DOMS, 24–72 hours after exercise).
Other Short-Term Effects
- Sweating increases to cool the body via evaporation.
- Skin reddening as blood vessels near the skin surface dilate to release heat.
- Energy system activation — the body shifts between aerobic and anaerobic energy systems depending on intensity.
Long-Term Effects of Exercise (Training Adaptations)
Regular training over weeks and months causes the body to adapt. These adaptations improve performance and health.
Cardiovascular Adaptations
| Adaptation | Benefit |
|---|
| Cardiac hypertrophy | The heart muscle (especially the left ventricle wall) grows thicker and stronger, enabling it to pump more blood per beat. |
| Increased stroke volume | A stronger heart ejects more blood per beat, both at rest and during exercise. |
| Lower resting heart rate (bradycardia) | Because stroke volume is higher, fewer beats are needed to circulate the same volume of blood. Elite athletes may have resting HR as low as 40 bpm. |
| Increased cardiac output during exercise | The trained heart can deliver a greater maximum cardiac output. |
| Increased capillarisation | More capillaries develop around muscles and alveoli, improving gas exchange and nutrient delivery. |
| Lower resting blood pressure | Healthier, more elastic blood vessel walls reduce resting blood pressure, lowering the risk of cardiovascular disease. |
| Increased red blood cell count | More red blood cells improve the blood's oxygen-carrying capacity. |
Respiratory Adaptations
| Adaptation | Benefit |
|---|
| Increased vital capacity | The lungs can hold more air, allowing greater oxygen intake. |
| Increased tidal volume at maximal exercise | Deeper breaths during intense activity. |
| Stronger respiratory muscles | The diaphragm and intercostal muscles become stronger, making breathing more efficient. |
| Improved gaseous exchange | Increased capillarisation around alveoli means more efficient O₂ and CO₂ exchange. |
Muscular and Skeletal Adaptations
| Adaptation | Benefit |
|---|
| Muscle hypertrophy | Muscles grow larger and stronger (particularly with resistance/strength training). |
| Increased muscular endurance | Muscles can work for longer without fatigue (particularly with aerobic training). |
| Increased tendon and ligament strength | Reduced risk of injury. |
| Increased bone density | Weight-bearing exercise stimulates bone growth, reducing osteoporosis risk. |
| Improved flexibility | Regular stretching increases the range of movement at joints. |
Body Composition and Metabolic Adaptations
- Reduced body fat percentage — regular exercise burns calories and can shift body composition towards a higher muscle-to-fat ratio.
- Increased metabolic rate — more muscle mass increases basal metabolic rate, burning more calories at rest.
- Improved ability to use fat as fuel — aerobic training teaches the body to use fat stores more efficiently during prolonged activity.
Exam Tips
- Be clear about the difference between short-term and long-term effects — the exam may ask you to distinguish them.
- Cardiac hypertrophy is a long-term adaptation; a temporary increase in heart rate is a short-term effect.
- When a question says "explain the effect of regular training on the cardiovascular system", they want long-term adaptations.
- Always link adaptations to performance benefits (e.g. "increased capillarisation improves oxygen delivery to working muscles, delaying fatigue").
- Remember: bradycardia (low resting HR) is a sign of a trained athlete, not a health problem.