In simple terms
A friendly intro before the formal notes — no formulas yet.
Your Body: The Ultimate Upgradeable Machine
When you exercise, your body makes immediate adjustments to cope with the demand. If you keep exercising regularly, it makes permanent upgrades to become more efficient and powerful.
Think of your body like a delivery van. A sudden large order (a single workout) means the driver has to speed up and the engine works hard (acute response). If large orders become the new normal (regular training), the company might upgrade to a van with a bigger, more fuel-efficient engine and a better cooling system (chronic adaptation) to handle the workload easily.
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Exercise begins, creating a 'stress' or demand for more oxygen and fuel in the muscles.
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The body responds immediately (acutely) by increasing heart rate, breathing rate, and redirecting blood flow to working muscles.
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After exercise, the body enters a recovery phase, repairing any micro-damage and replenishing energy stores, often building back slightly stronger (supercompensation).
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With repeated cycles of stress and recovery, the body undergoes long-term (chronic) structural and functional changes, such as a stronger heart and more efficient muscles, to better handle future exercise.
Explore the concept
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Key formulas
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$Q \ (L/min) = SV \ (L/beat) \times HR \ (beats/min)$
Full topic notes
Formal explanation with the rigour you need for the exam.
Acute Physiological Responses to Exercise
When exercise begins, the body makes immediate, short-term adjustments to meet the increased metabolic demand of the muscles. The sympathetic nervous system orchestrates these changes, which are designed to increase oxygen delivery and energy production. These responses are transient and the body returns to its resting state shortly after exercise ceases.
Cardiac Output: $Q \ (L/min) = SV \ (L/beat) \times HR \ (beats/min)$
Cardiovascular: Heart rate (HR), stroke volume (SV), and cardiac output (Q) all increase. Blood pressure rises, and blood is shunted away from non-essential organs (like the digestive system) towards the working muscles via vasodilation and vasoconstriction.
Respiratory: Ventilation rate and tidal volume increase to enhance oxygen uptake and carbon dioxide removal.
Muscular: Muscle temperature increases, motor unit recruitment rises, and the rate of metabolic reactions speeds up.
Chronic Adaptations to Endurance Training
When the body is subjected to repeated bouts of endurance exercise over several weeks or months, it undergoes long-term structural and functional changes. These adaptations make the body more efficient at performing aerobic activity. The principle of specificity dictates that these adaptations are most pronounced in the systems stressed by the training.
Cardiovascular: Cardiac hypertrophy (enlarged heart), increased resting and maximal stroke volume, decreased resting and sub-maximal heart rate, and increased blood volume.
Respiratory: Increased maximal ventilation and improved efficiency of gas exchange. However, the respiratory system is generally not considered a limiting factor for performance in healthy individuals.
Muscular & Metabolic: Increased number and size of mitochondria, increased myoglobin stores, enhanced capillarisation of muscles, and an increased capacity to oxidise fats for energy, sparing glycogen.
Chronic Adaptations to Strength Training
Resistance or strength training elicits a different set of adaptations compared to endurance training, primarily focused on the neuromuscular system. The initial gains in strength are largely due to neural adaptations, followed by muscular hypertrophy with continued training. These changes increase the muscle's ability to generate maximal force.
Muscular: Hypertrophy (increase in muscle fibre size), increased intramuscular stores of ATP, PC, and glycogen.
Neural: Improved motor unit recruitment, increased firing frequency of motor neurons, and reduced co-contraction of antagonist muscles.
Connective Tissue: Increased strength of tendons and ligaments, and increased bone mineral density.
When answering questions about adaptations, be specific. Instead of saying 'the heart gets better', state 'chronic endurance training leads to eccentric cardiac hypertrophy, increasing left ventricular volume and thus stroke volume'. Also, clearly differentiate between adaptations to endurance versus strength training, as they are distinct.
Overtraining and Ergogenic Aids
The balance between training stress and recovery is crucial for adaptation. If the training load is too high or recovery is insufficient, an athlete can enter a state of overtraining, leading to performance decrements and health issues. In the pursuit of performance, some athletes turn to ergogenic aids, which are substances or practices that enhance performance. Many of these are banned and carry significant health risks.
Overtraining Symptoms: Persistent fatigue, decreased performance, increased resting heart rate, mood disturbances, frequent illness.
Anabolic Steroids: Increase muscle mass and strength but can cause liver damage, cardiovascular disease, and mood swings.
Erythropoietin (EPO): Increases red blood cell count and oxygen-carrying capacity but thickens the blood, increasing the risk of heart attack and stroke.
Beta-Blockers: Reduce heart rate and anxiety, beneficial for precision sports, but can cause fatigue, low blood pressure, and are banned in many sports.
Worked examples
See the formulas applied — reveal one step at a time, like the exam.
An untrained 65 kg male has a resting heart rate (HR) of 72 bpm and a resting stroke volume (SV) of 75 ml/beat. After a 12-week cycling programme, his resting HR is 58 bpm and his resting SV has increased by 30%.
a) Calculate his resting cardiac output (Q) in L/min before training. (2 marks) b) Calculate his resting cardiac output (Q) in L/min after training. (3 marks) c) Explain the physiological reason for the decrease in his resting heart rate. (2 marks)
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a) Before Training:
- Formula:
- Calculation: [1]
- Conversion to L/min: [1 for correct answer with units]
An 80 kg powerlifter has a maximal oxygen uptake (VO2 max) of 3.6 L/min. A 65 kg marathon runner has a VO2 max of 4.5 L/min.
a) Calculate the relative VO2 max (in ml/kg/min) for both athletes. (4 marks) b) Explain why, despite the powerlifter's lower relative VO2 max, it is not a limiting factor for their sport. (2 marks)
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a) Relative VO2 Max Calculation:
- Powerlifter:
- Convert to ml/min: [1]
- Calculate relative: [1]
- Marathon Runner:
- Convert to ml/min: [1]
- Calculate relative: [1]
- Powerlifter:
How it all connects
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Glossary
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Quick check
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Revision flashcards
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Cardiac Output (Q)
The total volume of blood pumped by the heart per minute. It is the product of heart rate (HR) and stroke volume (SV). Formula: Q = HR × SV.
Key takeaways
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- ✓
Cardiovascular: Heart rate (HR), stroke volume (SV), and cardiac output (Q) all increase. Blood pressure rises, and blood is shunted away from non-essential organs (like the digestive system) towards the working muscles via vasodilation and vasoconstriction.
- ✓
Respiratory: Ventilation rate and tidal volume increase to enhance oxygen uptake and carbon dioxide removal.
- ✓
Muscular: Muscle temperature increases, motor unit recruitment rises, and the rate of metabolic reactions speeds up.
Practice — then mark it
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Test Your Knowledge on Exercise Physiology
Test Your Knowledge on Exercise Physiology
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