Big picture
Exercise physiology studies how the body responds and adapts to physical activity. When you train, your muscles, heart and lungs change: muscles grow stronger, the heart pumps more blood per beat, and breathing becomes more efficient. Understanding this helps athletes train well and stay healthy.
But sports also carry the risk of injuries, from scraped knees to broken bones. This chapter explains the physiological basis of fitness, the effects of exercise, how the body changes with age, the types of sports injuries, and how to give first aid.
Learning goals
Explain the physiological factors that determine strength, speed, endurance and flexibility.
Describe the effects of exercise on the muscular, cardiovascular and respiratory systems.
Explain physiological changes due to ageing.
Classify sports injuries and describe each type.
Describe the types of fractures and dislocations.
Explain first aid, including the PRICE principle.
Core ideas
1. Physiological factors determining components of fitness
Component | Physiological factors |
|---|---|
Strength | Muscle size (cross-sectional area), muscle fibre type (fast-twitch fibres generate more force), body weight, muscle composition, and the intensity of nerve impulses (recruitment of motor units) |
Speed | Fast-twitch muscle fibres, mobility of the nervous system (quick alternation between excitation and relaxation), explosive strength, elasticity and relaxing capacity of muscles, biochemical reserves (ATP-CP) and metabolic power |
Endurance | Aerobic capacity (VO₂ max), efficiency of the cardiovascular system, slow-twitch muscle fibres, energy stores (glycogen), lactic acid tolerance, and movement economy |
Flexibility | Joint structure (ball-and-socket joints allow more range), elasticity of muscles and ligaments, age and gender (children and females are generally more flexible), temperature (warm muscles stretch more), injury and strength of antagonist muscles |
Muscle fibres:
Slow-twitch (Type I, red): contract slowly, resist fatigue, rich in mitochondria and myoglobin; suited to endurance events.
Fast-twitch (Type II, white): contract quickly and powerfully, tire quickly; suited to sprints and power events.
2. Effects of exercise on the muscular system
Effect | Explanation |
|---|---|
Increase in muscle size (hypertrophy) | Muscle fibres become thicker with strength training |
Increase in strength and endurance | Muscles produce more force and work longer without fatigue |
Better posture and shape | Toned muscles support correct posture |
More capillaries and mitochondria | Better supply of oxygen and nutrients; better energy production |
Increased glycogen stores | More fuel available |
Delayed fatigue and faster recovery | Better removal of lactic acid |
Improved reaction time and coordination | Better nerve–muscle coordination |
3. Effects of exercise on the cardiovascular system
Effect | Explanation |
|---|---|
Increase in heart size (athlete's heart) | The heart muscle becomes stronger and larger |
Increase in stroke volume | More blood is pumped per beat |
Increase in cardiac output | Cardiac output = stroke volume × heart rate increases during exercise |
Lower resting heart rate | A trained heart pumps more per beat, so it beats less often at rest (endurance athletes may have resting rates around 40–60 beats per minute) |
Faster recovery | The heart rate returns to normal more quickly after exercise |
More capillaries and blood volume | More haemoglobin and red blood cells carry more oxygen |
Lower blood pressure and cholesterol | Regular exercise reduces the risk of heart disease |
Cardiac output example. Stroke volume 70 mL × heart rate 72 beats per minute = 5,040 mL, or about 5 litres per minute at rest.
4. Effects of exercise on the respiratory system
Effect | Explanation |
|---|---|
Increase in vital capacity | More air can be breathed out after a deep breath |
Increase in tidal volume | More air per breath |
Lower resting breathing rate | Efficient lungs need fewer breaths at rest |
Stronger respiratory muscles | The diaphragm and intercostal muscles become stronger |
More alveoli active and better gas exchange | More oxygen enters the blood |
Increased oxygen debt tolerance | The body handles oxygen debt better |
Greater VO₂ max | Maximum oxygen uptake increases |
5. Physiological changes due to ageing
Muscular system: loss of muscle mass and strength (sarcopenia), slower reactions.
Skeletal system: loss of bone density (osteoporosis), stiffer joints, less flexibility.
Cardiovascular system: lower maximum heart rate and cardiac output, stiffer arteries, higher blood pressure.
Respiratory system: lower vital capacity and lung elasticity.
Nervous system: slower nerve conduction, poorer balance and coordination, memory decline.
Metabolism: lower BMR, tendency to gain fat.
Role of exercise: regular activity slows these changes, maintains strength, bone density, balance and heart health, and helps older adults remain independent.
6. Sports injuries: classification
Soft tissue injuries (skin, muscles, ligaments, tendons):
Injury | Description |
|---|---|
Abrasion | Scraping of the skin, as when a player falls on a rough surface |
Contusion | A bruise: bleeding under the skin from a blow by a blunt object, without breaking the skin |
Laceration | An irregular tear of the skin caused by a blunt or sharp object, such as a spike |
Incision | A clean, straight cut by a sharp object such as a blade or glass |
Sprain | An injury to a ligament (which joins bone to bone), from twisting a joint, as at the ankle or wrist |
Strain | An injury to a muscle or tendon (which joins muscle to bone), from overstretching or overuse, as in a hamstring pull |
Bone and joint injuries:
Injury | Description |
|---|---|
Dislocation | The bones of a joint are displaced from their normal position; common at the shoulder, fingers, hip, knee and jaw |
Fracture | A break or crack in a bone |
Types of fractures:
Fracture | Description |
|---|---|
Simple (closed) | The bone breaks but doesn't pierce the skin |
Compound (open) | The broken bone pierces the skin, with risk of infection |
Complicated | The fracture also damages nearby organs, nerves or blood vessels |
Greenstick | The bone bends and cracks on one side without breaking completely; common in children whose bones are soft |
Comminuted | The bone breaks into more than two pieces |
Transverse | The break is straight across the bone, at right angles to its length |
Oblique | The break runs diagonally across the bone |
Impacted | The broken ends are driven into each other |
Stress fracture | Tiny cracks from repetitive stress, common in runners |
7. First aid and the PRICE principle
First aid is the immediate help given to an injured person before medical help arrives, to save life, prevent the injury from worsening and promote recovery.
PRICE for soft tissue injuries (sprains, strains, contusions):
Step | Action |
|---|---|
P – Protection | Protect the injured part from further harm (stop play, use support) |
R – Rest | Rest the injured part; avoid using it |
I – Ice | Apply ice (wrapped in a cloth) for about 15–20 minutes every few hours for the first 24–48 hours, to reduce swelling and pain |
C – Compression | Apply a firm (not too tight) elastic bandage to limit swelling |
E – Elevation | Raise the injured part above heart level to reduce swelling |
First aid for specific injuries:
Abrasion, laceration, incision: clean the wound with water or antiseptic, stop bleeding with pressure, and cover with a sterile dressing; deep cuts need stitches and a tetanus injection.
Dislocation: don't try to reset the joint; immobilise it with a sling or splint and get medical help.
Fracture: don't move the injured part; immobilise it with a splint, control bleeding in compound fractures, treat for shock, and get medical help immediately.
Prevention of injuries: proper warm-up and cool-down, correct technique, suitable equipment and footwear, gradual increase in training load, adequate rest, good nutrition and hydration, and following rules.
A reliable approach to questions
For each fitness component, list three or four physiological factors.
Describe the effects of exercise system by system.
Classify injuries as soft tissue or bone and joint, and define each type.
Distinguish sprain (ligament) and strain (muscle or tendon).
Describe fracture types, and give first aid using PRICE and immobilisation.
Connections that matter
Training in sports explains how training produces these adaptations.
Biomechanics and sports explains forces that cause injuries.
Biology: locomotion and movement explains the structure of muscles, bones and joints.
Common mistakes
Mixing up sprain and strain. A sprain affects a ligament; a strain affects a muscle or tendon.
Saying exercise increases resting heart rate. Training lowers resting heart rate.
Applying ice directly on the skin for a long time. Wrap ice in cloth and apply for 15–20 minutes.
Trying to put a dislocated joint back in place during first aid.
Revision checklist
I can explain physiological factors for strength, speed, endurance and flexibility.
I can describe the effects of exercise on three body systems.
I can explain physiological changes due to ageing.
I can classify and describe sports injuries and fracture types.
I can apply first aid and the PRICE principle.