Acceleration – The rate of change of velocity over time.

Acute injury – A sudden injury from trauma or impact.

Acute response – An immediate body reaction to exercise.

Adduction – Movement toward the midline of the body.

Aerobic capacity – Maximum oxygen use during sustained exercise.

Aerobic respiration – Energy production using oxygen.

Agility – Ability to change direction quickly with control.

Altitude training – Training at high elevation to improve endurance.

Anaerobic glycolysis – Energy production without oxygen, creating lactic acid.

Anaerobic respiration – Short-term energy without oxygen.

Antagonist muscle – The muscle that opposes the prime mover.

Arteriovenous oxygen difference (a-vO2 diff) – Oxygen difference between arteries and veins.

Arousal – A physical and mental state of readiness.

ATP (Adenosine Triphosphate) – The body’s main energy molecule.

ATP-PC system – Fast, anaerobic energy system for short bursts.

Atrophy – Muscle wasting due to inactivity.

Autonomic nervous system – Controls involuntary functions like heart rate.

Axial skeleton – Central part of the skeleton including skull, spine, and ribs.

Axis of rotation – Imaginary line about which movement occurs.

Afferent neuron – Nerve that carries sensory info to the brain.

Active flexibility – Range of movement using voluntary muscle effort.

Active recovery – Light activity to aid recovery post-exercise.

Action potential – Electrical signal sent along nerves to muscles.

Adaptation – The body’s long-term response to training.

Aerobic training zone – Target heart rate zone to improve endurance.

Agonist – The primary muscle responsible for movement.

All-or-none law – Muscle fibres contract fully or not at all.

Alveoli – Tiny air sacs in lungs for gas exchange.

Anaerobic threshold – Point where lactate rapidly accumulates.

Angular motion – Movement around a fixed point or axis.

Angular velocity – Speed of rotation around an axis.

Anterior – The front of the body or a body part.

Anticipation – Predicting a movement before it happens.

Aponeurosis – A flat sheet of connective tissue attaching muscle to bone.

Arteriole – A small blood vessel that controls blood flow to capillaries.

Arrhythmia – An irregular heartbeat or cardiac rhythm.

Articulation – A joint or the point where bones meet.

Assisted stretch – A stretch that is helped by another person or equipment.

Athlete-centred coaching – Coaching approach that focuses on the athlete's needs.

ATP resynthesis – The process of regenerating ATP for energy.

Attentional focus – The ability to concentrate on relevant cues.

Auditory feedback – Information received through hearing during performance.

Autogenic inhibition – A reflex that causes a muscle to relax after prolonged tension.

Autonomy – A person’s sense of control over their actions.

Avascular – Lacking blood vessels (e.g., cartilage).

Axon – The part of a neuron that carries signals away from the cell body.

Absolute strength – The total force an individual can produce.

Accuracy – The precision of a skill performance or movement.

Acceleration phase – The stage of movement where speed increases.

Activity threshold – The minimum intensity required to produce training adaptations.