Haematocrit – The percentage of red blood cells in a sample of blood.

Haemoglobin – The protein in red blood cells that transports oxygen.

Haemostasis – The process that stops bleeding, involving blood clotting.

Hardiness – A personality trait linked to resilience and coping under pressure in sport.

Haversian system – The structural unit of compact bone that contains blood vessels and nerves.

Hawthorne effect – A change in behaviour when individuals know they are being observed.

Hazard perception – The ability to identify potential risks in the sporting environment.

HDL cholesterol – "Good" cholesterol that helps remove excess fats from the bloodstream.

Health-related fitness – Physical traits associated with good health, such as endurance and flexibility.

Health screening – A process to identify any risk factors before starting physical activity.

Heart murmur – An unusual sound from the heart often caused by valve issues.

Heart rate reserve (HRR) – The difference between resting and maximum heart rate, used to calculate training zones.

Heat acclimatisation – Physiological adaptation that improves tolerance to exercising in hot environments.
Heat exhaustion – A condition caused by overheating, leading to heavy sweating and weakness.

Heatstroke – A life-threatening condition caused by extreme overheating, with a failure to regulate body temperature.

Heel strike – The part of the gait cycle where the heel first contacts the ground.

Helper T-cells – Immune cells that aid in the body’s defence and recovery processes.

Hematoma – A collection of blood outside blood vessels, usually caused by trauma.

Hemiplegia – Paralysis affecting one side of the body, sometimes following stroke or head injury.

Henderson-Hasselbalch equation – A formula used to understand pH balance in blood during exercise.

Henneman’s size principle – The recruitment of motor units from smallest to largest based on demand.

Hepatic portal system – A blood vessel system that carries nutrients from the intestines to the liver.

Heredity – The genetic transmission of traits from parents to offspring.

High-density training – A training method involving high volume in a short time with limited rest.

High-impact exercise – Activities that involve strong ground contact forces, such as jumping.

High-intensity interval training (HIIT) – A workout method alternating between intense activity and recovery.

High-performance culture – An environment that promotes excellence, accountability, and continuous improvement.

Hinge joint – A synovial joint allowing movement in one direction, like the elbow or knee.

Hip flexors – A group of muscles that bring the thigh towards the abdomen.

Histology – The microscopic study of tissues, including muscle and connective tissues.

Homeostasis – The body’s ability to maintain a stable internal environment.

Homologous transfusion – Blood doping using blood from a compatible donor.

Horizontal adduction – Moving a limb across the body in a horizontal plane.

Horizontal abduction – Moving a limb away from the midline in a horizontal plane.

Hormonal response – The release of hormones due to exercise or stress.

Hormone replacement therapy (HRT) – Medical treatment that replaces declining hormones, sometimes used in athlete recovery.

Hormones – Chemical messengers that regulate body processes like growth, metabolism, and recovery.

Humerus – The upper arm bone between the shoulder and elbow.

Humoral regulation – Control of physiological functions through substances in body fluids, like hormones.

Hyaline cartilage – Smooth tissue covering the ends of bones in joints to reduce friction.

Hydration status – The balance of fluids in the body, crucial for performance.

Hydrostatic weighing – A method of measuring body composition using water displacement.

Hyperextension – Movement that increases a joint angle beyond the normal range.

Hyperplasia – An increase in the number of muscle fibres, often theorised in advanced training.

Hypertensive response – An abnormally high rise in blood pressure during exercise.

Hypertrophy – An increase in muscle size due to resistance training.

Hyperventilation – Rapid breathing that may reduce carbon dioxide levels too quickly.

Hypoglycaemia – A condition where blood sugar drops too low, affecting energy and concentration.

Hypokinetic condition – A health problem caused by physical inactivity, such as obesity or heart disease.

Hypothalamus – A brain region that helps regulate temperature, hunger, and hormone release.

Hypoxic training – Training in low-oxygen conditions to stimulate adaptation and improve endurance.