Physiology and Injuries in Sport

Main Idea

Exercise produces immediate physiological responses and longer-term adaptations in the muscular, circulatory, respiratory, and nervous systems. Training should be planned according to the desired ability, such as strength, endurance, speed, or flexibility, while incorporating prevention, recovery, appropriate first aid, rehabilitation, and a gradual return to activity after injury.

Key Concepts and Definitions

• Physiology: The study of how the human body functions and responds to exercise.
• Exercise Physiology: The study of changes in body systems during physical activity and training.
• Muscular System: The body system responsible for movement, posture, stability, and production of force.
• Circulatory System: The heart and blood vessels that transport oxygen, nutrients, hormones, and waste products.
• Respiratory System: The organs and passages involved in breathing and the exchange of oxygen and carbon dioxide.
• Cardiac Output: The amount of blood pumped by the heart in one minute; it equals heart rate multiplied by stroke volume.
• Stroke Volume: The amount of blood pumped by the left ventricle during one heartbeat.
• Heart Rate: The number of heartbeats per minute.
• Maximum Oxygen Uptake (VO2 max): The highest amount of oxygen the body can use during intense exercise and an important measure of aerobic endurance.
• Aerobic Capacity: The ability of the body to produce energy using oxygen during prolonged activity.
• Anaerobic Capacity: The ability to produce energy without sufficient oxygen during short, intense activities.
• Energy Systems: The ATP-PC system, anaerobic glycolysis system, and aerobic system that supply energy for physical activity.
• ATP-PC System: A rapid energy system using stored ATP and phosphocreatine for very short, explosive efforts.
• Anaerobic Glycolysis: The breakdown of glucose without enough oxygen to provide energy for high-intensity activity lasting roughly several seconds to about two minutes.
• Aerobic Energy System: The oxygen-dependent system that produces energy for longer-duration, lower- or moderate-intensity activities.
• Warm-up: Low- to moderate-intensity activity that gradually prepares the body for exercise by increasing temperature, blood flow, and joint mobility.
• Cool-down: Gentle activity after exercise that gradually lowers heart rate and supports recovery.
• Flexibility: The range of movement possible at a joint.
• Strength: The ability of a muscle or muscle group to exert force against resistance.
• Endurance: The ability to continue physical activity for a prolonged period while resisting fatigue.
• Fatigue: A temporary reduction in the ability of muscles or the body to perform effectively.
• Sports Injury: Damage to body tissues caused during exercise, training, or competition.
• Acute Injury: An injury that occurs suddenly, such as a fracture, sprain, or dislocation.
• Chronic Injury: An injury that develops gradually because of repeated stress or overuse.
• Soft-Tissue Injury: Damage to muscles, ligaments, tendons, or skin.
• Sprain: An injury caused by stretching or tearing of a ligament around a joint.
• Strain: An injury involving overstretching or tearing of a muscle or tendon.
• Contusion: A bruise caused by a blow that damages small blood vessels under the skin.
• Abrasion: A scrape in which the surface layer of skin is rubbed or torn away.
• Laceration: A cut or tear in the skin or body tissue.
• Fracture: A partial or complete break in a bone.
• Dislocation: An injury in which the bones at a joint are forced out of their normal position.
• Stress Fracture: A small crack in a bone caused by repeated loading or overuse.
• Tendonitis: Inflammation or irritation of a tendon, often caused by repeated activity.
• RICE or PRICE Method: A basic early-care approach involving protection, rest, ice, compression, and elevation; medical advice should be sought when needed.
• Rehabilitation: A planned process of restoring movement, strength, flexibility, and function after injury.
• Overtraining: A condition caused by excessive training and insufficient recovery, leading to persistent fatigue and reduced performance.

Supporting Arguments and Evidence

• Exercise causes immediate increases in heart rate, breathing rate, cardiac output, body temperature, blood flow to working muscles, and energy demand. Cardiac output is calculated as:

Cardiac output = heart rate × stroke volume.

During exercise, heart rate can be estimated by counting the pulse and converting it to beats per minute.

• Regular training produces longer-term adaptations. Endurance training generally improves stroke volume, aerobic capacity, circulation, and recovery ability. It may also lower resting heart rate and improve oxygen delivery. Strength training can increase muscle size, strength, power, bone strength, and neuromuscular coordination. Training may also improve flexibility and coordination.

• The energy system used depends mainly on the intensity and duration of activity. The ATP-PC system supports very short, explosive efforts such as jumping, throwing, or a short sprint. Anaerobic glycolysis becomes important during high-intensity activities lasting longer than the immediate ATP-PC supply, roughly several seconds to about two minutes. The aerobic system is dominant during prolonged activities such as distance running, swimming, and cycling.

• Training should be structured according to key principles. Overload means applying a training demand greater than the body is accustomed to, while progression means increasing that demand gradually and safely. Specificity means that adaptations relate to the activity, muscles, energy system, and movement pattern trained. Reversibility means that fitness gains may decline when training is reduced or stopped for a prolonged period. Individual differences, variation, and adequate recovery must also be considered.

• Prevention is safer and more effective than treatment. Common causes of injury include inadequate warm-up, poor technique, overuse, sudden increases in training load, unsuitable equipment, unsafe playing surfaces, collisions, dehydration, and fatigue. Primary prevention includes fitness conditioning, proper technique, protective equipment, hydration, adequate nutrition, safe facilities, and planned rest. A warm-up increases body temperature, blood flow, and joint mobility, while a cool-down gradually lowers heart rate and supports recovery.

• Recovery is necessary to prevent fatigue and overtraining. Adequate sleep, hydration, nutrition, rest intervals, and recovery sessions help maintain performance and reduce excessive physiological stress. Excessive training combined with insufficient recovery can produce persistent fatigue, reduced performance, and overtraining.

• Injury management should prioritize safety. The activity should be stopped and the condition assessed. A suspected fracture or dislocation should not be forcefully moved or straightened; qualified medical attention is required. For bleeding, gentle direct pressure should be applied with a clean dressing when safe, and medical help should be sought for severe or uncontrolled bleeding. For soft-tissue injuries, the area should be protected, aggravating activity stopped, and appropriate cooling used during the early stage. Medical advice is necessary if pain or swelling is severe.

• Urgent medical evaluation is required for persistent pain, worsening swelling, loss of movement, numbness, deformity, loss of consciousness, or breathing difficulty. The RICE or PRICE method provides a basic early-care approach involving protection, rest, ice, compression, and elevation, but it does not replace professional assessment when required.

• Rehabilitation restores movement, strength, flexibility, and function after injury. Return to sport should be gradual and should begin only when pain and swelling are controlled and normal movement, strength, and sport-specific function have returned. Returning before adequate healing increases the risk of further injury.

What to Remember

Exercise produces immediate changes in heart rate, breathing, cardiac output, temperature, blood flow, and energy demand, while regular training creates longer-term adaptations. Effective training applies overload and progression while respecting specificity, individuality, recovery, and reversibility. Injury prevention, safe first aid, rehabilitation, and a gradual return to sport are essential for improving performance while protecting health.