Saccade – A rapid movement of the eye between two fixed points, important in visual tracking.

Sacroiliac joint – The joint between the sacrum and pelvis, relevant in lower back stability.

Sacrum – A triangular bone at the base of the spine, involved in pelvic alignment.

Sagittal plane – The anatomical plane dividing the body into left and right halves.

Salivary cortisol – A non-invasive measure of stress hormone levels in athletes.

Sarcopenia – Age-related loss of muscle mass and function.

Sarcoplasm – The fluid within muscle fibres where energy reactions occur.

Sarcoplasmic hypertrophy – Muscle growth characterised by increased fluid and energy storage in fibres.

Sarcoplasmic reticulum – The structure within muscle fibres that stores and releases calcium for contraction.

Satellite cells – Muscle stem cells involved in repair and regeneration after exercise.

SAQ training – Speed, agility and quickness drills used to improve athletic movement.

Saturated fat – A type of dietary fat that should be limited in athlete nutrition plans.

SA node – The heart’s natural pacemaker, initiating each heartbeat.

Scalar quantity – A measurement with only magnitude (e.g. speed, distance).

Scapula – The shoulder blade, essential for upper-body movement and stability.

Scapular stabilisation – The control of shoulder blade movement, important for upper-body strength.

Scientific method – A structured process for conducting valid and reliable research in sport science.

Sebum – An oily skin secretion that can increase with exercise or stress.

Sedentary behaviour – Prolonged periods of sitting or low physical activity, linked to health risks.

Selective attention – Focusing on relevant cues during performance while ignoring distractions.

Self-efficacy – A person’s belief in their ability to perform a task successfully.

Self-paced skill – A skill initiated and controlled by the performer, such as a golf swing.

Self-report – A method of collecting psychological or behavioural data directly from participants.

Self-talk – Internal dialogue used to regulate thoughts and emotions in sport.

Semilunar valves – Heart valves that prevent backflow of blood from arteries into the heart.

Sensorimotor control – The integration of sensory input and motor output to guide movement.

Sensory adaptation – Reduced sensitivity to repeated stimuli, relevant in fatigue and reaction tasks.

Sensory feedback – Information received from the body and environment during or after movement.

Sensory memory – The brief retention of sensory information, supporting reaction and learning.

Sequential skills – Complex motor tasks performed in a fixed, logical order (e.g. gymnastics routine).

Set – A group of repetitions performed without rest in resistance training.

Set point theory – The idea that the body maintains a stable weight through internal regulation.

SFO (subfornical organ) – A brain structure involved in thirst and fluid regulation.

Shank – The lower leg segment between knee and ankle, important in running mechanics.

Sharpey's fibres – Connective tissues that anchor tendons and ligaments to bone.

Shear force – A force that acts parallel to a surface, relevant in joint injury.

Shin splints – Pain along the shin due to overuse or poor biomechanics.

Shivering – An involuntary response to cold that generates heat through muscle activity.

Shock absorption – The body's or equipment’s ability to reduce impact forces during activity.

Short-term memory – The temporary storage of information used during tasks or learning.

Short-twitch fibres – Often used to describe fast-twitch fibres; a mislabel for rapid muscle contractions.

Shoulder girdle – The bony structure, including the scapula and clavicle, supporting arm movement.

Shuttle run – A back-and-forth running test used to assess aerobic or agility performance.

Sickle cell trait – A genetic condition affecting oxygen transport during intense exercise.

Sigmoid function – A curve representing gradual, then rapid, then plateaued learning or adaptation.

Significant result – A statistically meaningful outcome, not likely due to chance.

Simple carbohydrate – A fast-digesting sugar used for quick energy.

Simple reaction time – The time taken to respond to a single stimulus.

Simulated altitude training – Training in reduced oxygen environments to improve aerobic capacity.

Single joint exercise – A movement that uses only one joint (e.g. leg extension).

Skill – The learned ability to bring about predetermined results with maximum efficiency.

Skill acquisition – The process of learning or developing new abilities in sport.

Skill transfer – The influence of one skill on the learning or performance of another.

Skill-related fitness – Fitness components that support performance: agility, balance, coordination, etc.

Skinfold measurement – A method for estimating body fat by measuring skin thickness.

Sleep hygiene – Behavioural and environmental practices that promote good-quality sleep.

Sleep inertia – The grogginess and reduced performance immediately after waking.

Sliding filament theory – The model explaining how muscles contract through actin and myosin interaction.

Slow oxidative fibres – Type I muscle fibres suited for endurance due to high aerobic capacity.

Slow-twitch fibres – Muscle fibres that are fatigue-resistant and used for endurance activities.

Smart goal – A goal-setting method using Specific, Measurable, Achievable, Relevant, and Time-bound criteria.

Snatch – An Olympic lift moving a barbell from floor to overhead in one motion.

Social comparison – Evaluating performance by comparing oneself to others.

Social facilitation – Improved performance in the presence of others during simple tasks.

Social inhibition – Decreased performance in front of others during complex or unfamiliar tasks.

Social loafing – Reduced effort by individuals when working in a group.

Sodium – An electrolyte critical for fluid balance and nerve function in exercise.

Sodium-potassium pump – A cell membrane mechanism that helps restore resting potential.

Soft tissue – Muscles, tendons, ligaments and skin, often involved in sport injuries.

Somatic nervous system – The part of the nervous system that controls voluntary movement.

Somatotype – A classification of body type (endomorph, mesomorph, ectomorph).

Somatotyping – The process of categorising athletes based on physique.

Specificity – A training principle stating that adaptations are specific to the stimulus applied.

Specific dynamic action – The energy used during digestion and nutrient processing.

Specific warm-up – Movements that mimic the sport or activity to be performed.

Spectator effect – The impact that being watched has on athletic performance.

Speed – The ability to move quickly across the ground or through movement.

Speed endurance – The ability to maintain high speed over an extended period.

Speed-strength – The ability to produce high force in minimal time, e.g. in sprints or throws.

Sphygmomanometer – A device used to measure blood pressure.

Spinal cord – The central pathway of the nervous system, controlling motor and sensory input.

Spinal reflex – An involuntary response triggered by the spinal cord without brain involvement.

Spirulina – A nutrient-rich algae supplement sometimes used by athletes.

Spirulina platensis – A specific strain of spirulina studied for anti-fatigue and antioxidant effects.

Spirometry – A method for measuring lung volume and breathing capacity.

Spontaneous recovery – The reappearance of a learned response after extinction in psychology.

Sport education model – A curriculum model that promotes team roles, competition and responsibility.

Sport psychology – The study of mental factors that affect athletic performance.

Sport-specific training – Training methods closely replicating the demands of a particular sport.

Sportsmanship – Ethical behaviour and fair play in sport.

Spotting – Assisting a person during resistance exercises to ensure safety.

Squat – A fundamental strength exercise targeting the lower body.

Stabiliser muscle – A muscle that supports joint stability during movement.

Stages of learning – Cognitive, associative and autonomous phases of skill development.

Standard deviation – A measure of variation within a set of data.

Standardisation – Ensuring consistency in the way a test or protocol is applied.

Static balance – The ability to maintain posture while stationary.

Static stretching – Holding a stretch position for a period to increase flexibility.

Sternocleidomastoid – A neck muscle involved in head movement and posture.

Stimulus – A signal that elicits a response, often used in reaction time testing.

Stroke volume – The amount of blood pumped out of the heart per beat.

Structural fatigue – The weakening of a material or body structure due to repeated stress.

Subcutaneous fat – Fat stored under the skin, measured in body composition tests.

Submaximal test – A fitness test performed below maximum effort to estimate capacity.

Supination – The outward rotation of the forearm or foot.

Supine – A body position lying face upward, used in many testing and training contexts.