A
abdomen region of the body between the thorax (separated from it by the diaphragm) and the pelvis; colloquial belly. The abdominal wall consists of skin, connective tissue including a variable amount of fat, and muscles. A continuous thin membrane, the peritoneum, lines the wall and covers all the organs in the abdominal cavity. See fig appendix 1.4.
abdominal breathing see diaphragm.
abdominal cramps tight, constrictive, usually intermittent abdominal discomfort, usually the result of spasm of an internal organ, e.g. bowel spasm related to gastroenteritis or menstrual cramps. Not to be confused with muscular cramp from contraction of the abdominal wall musculature, possibly secondary to trauma. See also stitch.
abdominal injury damage to the abdomen and/or its contents. Can occur in sport, especially contact sports. Injury may be superficial, to the abdominal wall only, but significant trauma can damage the internal organs and lead to significant blood loss. Accumulation of blood in the abdominal cavity may be undetected, with potential fatality.
abdominal muscles layers of muscle in the abdominal wall. The rectus abdominis muscles, strap-like, lie vertically each side of the midline; their action can be important in breaking the force of a blow. A ‘three-ply’ layer of flat muscles, each with the fibres running in different directions (external and internal oblique, and transverse) extend from the lower ribs to the hip bone, and from the sheath of the rectus muscles to the lumbar spine, thickest in the flanks. Actions include: forward flexion and rotation of the trunk; assisting expiration during deep breathing or against airway obstruction, by contracting as the diaphragm relaxes, or acting together with the contracting diaphragm to raise abdominal pressure in straining (urination, defaecation, childbirth) and in vomiting. See appendix 1.2 fig 4.
abdominal pain discomfort in the abdomen which may result from a variety of medical conditions related to one or other of the abdominal organs, or from injury, particularly during contact sports. Medical advice should be sought and physical activity should cease.
abduction movement sideways of the arm at the shoulder, of the leg at the hip, of a finger, thumb or toe away from the middle of the hand or foot; abductor a muscle with this action; opposite of adduction. See appendix 1.2 fig 3.
ability the physical and/or cognitive capability to perform a task without further training. perceived ability a person’s perception of their specific abilities within a given domain, such as in football versus in another sport. See also capacity, skill, performance.
abrasion superficial injury to skin or mucous membrane from scraping or rubbing.
absolute threshold in psychophysics, the smallest magnitude of a sensory input that can be detected, typically defined as the magnitude that can be detected over a proportion of presentations (e.g. 75%). Also known as absolute limen. See also difference threshold.
absorption see intestinal absorption.
acceleration change in motion of a body or object: the rate of change of velocity with respect to time. linear acceleration: the rate of change in linear velocity with respect to time; related to force by Newton’s second law of motion (often stated as force = mass×linear acceleration). Measured in metres per second squared (m.s−2). angular acceleration: the rate of change in angular velocity with respect to time. Measured in degrees per second squared (°. s−2) or radians per second squared (rad.s−2); related to moment by Newton’s second angular law of motion (moment = moment of inertia×angular acceleration). tangential acceleration: the acceleration of an object or body acting at a tangent to its direction of motion, e.g. when it is moving in a circle or around a curve. instantaneous acceleration: acceleration measured over a very short (infinitesimal) period of time, effectively a continuous measurement of acceleration. See also gravitational acceleration.
accessory bone the os trigonum in the ankle joint – a bone present in only <10% of the population. In practice, rarely injured in sport but can be confused on X-ray with an avulsed fragment of bone or loose body.
accident rates accidents are common in sport, particularly in contact sports, and result in a significant workload for hospital A&E departments. Currently there are 20 million sports injuries in the UK each year, 50% of them football related, at an estimated cost in treatment and lost productivity of £1 billion.
acclimation artificial approximation to natural acclimatization, to either heat or altitude, achieved by exposure in a thermal or hypobaric chamber for several hours a day, typically for 2–3 weeks before going to the challenging new environment.
acclimatization adjustment of physiological processes in response to a change from the accustomed environment: to heat or cold, or to high altitude. For example, repeated exercise in the heat leads to an increase in maximal sweating rate, but with reduced sodium concentration in the sweat; low oxygen content in the blood at high altitude leads among other adjustments to increased breathing and cardiac output, assisting oxygen supply. See also altitude acclimatization, heat acclimatization, sweating.
acetabulum (from the Latin for a vinegar-cup) the cup-shaped cavity on each side of the pelvis into which the head of the femur fits, forming the ‘ball-and-socket’ of the hip joint. See appendix 1.2 fig 1.
acetylcholine (ACh) a substance made in certain nerve cells and released from their axon terminals at a junction or synapse in the process of cholinergic transmission of impulses (1) from motor nerves to skeletal muscle, (2) from one nerve to another in the nervous system (in the brain, and in autonomic ganglia), (3) at parasympathetic nerve endings (e.g. those that slow down the heart rate, stimulate secretion from glands or activate smooth muscle in the gut). Cholinergic receptors occur in two different pharmacological groups: nicotinic, e.g. at skeletal muscle motor endplates, and muscarinic, e.g. in cardiac and smooth muscles. See also neuromuscular junction, neurotransmitter, parasympathetic nervous system.
acetyl coenzyme A an important metabolic intermediate, involved in various metabolic pathways, including glucose and fatty acid oxidation, and degradation of some amino acids. It also represents a key intermediate in lipid biosynthesis. Commonly referred to as acetyl CoA. See also Krebs cycle.
acetylsalicylic acid better known as aspirin. Developed by the pharmaceutical group Bayer in Germany in 1899. Used at lower doses (2–3 g per day) as an analgesic and antipyretic. At higher doses (>4 g per day) it is a very powerful anti-inflammatory agent and therefore effective in soft tissue injury, but its use is limited by gastric side effects. See also non-steroidal anti-inflammatory drugs.
achievement goal a goal focused on demonstrating high ability to oneself or others, or to avoid demonstrating low ability.
achievement goal orientation a person’s general tendency to act in an ego-involved or task-involved manner.
achievement motivation form of motivation characterized by a competitive drive to meet high standards of performance, also known as need for achievement.
Achilles tendon a large tendon (aka tendo calcaneus) at the back of the ankle, joining the main calf muscles (gastrocnemius and soleus) to the heel bone (calcaneum). The tendon is commonly injured in sport either by direct trauma (resulting in partial or complete rupture) or by repeated micro-trauma or overuse resulting in inflammation. Achilles tendonitis is most commonly the result of poor technique, poor footwear, hard running surface, high-intensity or long-distance running. Treatment is with RICE, anti-inflammatory medication, a heel raise and correction of causes. Surgery may be required in severe cases. Achilles bursitis is inflammation of the bursa (a ‘bag’ of fluid) that separates the tendon from the back of the calcaneum. See appendix 1.2 fig 6.
acidaemia lower than normal pH of the blood. See also acidosis.
acid–base balance refers to the mechanisms that keep body fluids close to their normal pH (i.e. neither too alkaline nor too acidic), vital for normal cellular function. See also acidosis, alkalosis.
acidosis condition due to decrease in pH of body fluids, from accumulation of acid or depletion of alkali. metabolic acidosis can occur by accumulation of H+ during high-intensity exercise, due mainly to an increased rate of anaerobic glycolysis and therefore of lactic acid production. Pathological causes include diabetic ketoacidosis and severe kidney disease. respiratory acidosis is caused by carbon dioxide retention due to inadequate ventilation, in lung disease, or in respiratory depression by drugs. In compensated acidosis pH may be normal, with a high blood bicarbonate concentration (due to increased renal retention) when the cause was respiratory, or with a low blood carbon dioxide (due to hyperventilation) when the cause was metabolic. See also glycolysis, lactic acid.
acquired immune deficiency syndrome (AIDS) denotes a particular stage of infection with the human immunodeficiency virus (HIV). The criteria for defining an illness as AIDS, in a person infected with HIV, are those of the US Centers for Disease Control and Prevention (CDC); they include certain infections and cancers, and/or specified low levels of immune system cells in the blood.
acromioclavicular joint the small synovial joint above the shoulder, between the outer end of the clavicle and the acromion process of the scapula, linking them to form the shoulder girdle. Parts of the trapezius and deltoid muscles are attached to the joint capsule. Commonly injured in contact sports especially rugby. See appendix 1.2 fig 4A.
actin globular protein molecule which readily links with others (with consumption of ATP) to form long, double-helical strands. Such actin filaments are found in a wide variety of animal and plant cells, as well as forming the structural core and main (but not only) component of the thin filaments in the myofibrils of all animal muscles. Actin is thus a protein of great evolutionary antiquity and vertebrate striated muscles are unusual only in having a very high content of it (80% of total protein), and in its highly ordered locations within the cells, where thin filaments alternate with thick filaments containing actin’s partner protein myosin, to form the cross-striated pattern. See also muscle, muscle fibres; appendix 1.2 fig 7.
action in addition to its general meaning, the name for a force applied to a body or object. Often used with reactionin a simple expression of Newton’s third law of motion.
action potential (AP) transient voltage change propagating along the membrane of nerve, muscle or other excitable cell; the means whereby information flows rapidly along the cell’s length. Triggered by a small depolarization, an AP consists of further depolarization and often an overshoot to an inside-positive membrane potential. The depolarization/positive swing is caused by the inflow of sodium and/or calcium ions, according to the tissue, and the return to normal inside-negative potential by the subsequent outflow of potassium ions. Metabolic energy is used in maintaining the differences between the intracellular and extracellular concentrations of these ions, but not in the AP itself. See also electromyography (EMG), nerve fibre, neuromuscular junction, sarcoplasmic reticulum (SR), t-tubes.
activation initiation of a response in an effector (i.e. a muscle or gland).
active movement movement by the person’s own effort, as distinct from passive movement.
actomyosin ATPase see muscle enzymes.
acupuncture the practice of inserting fine needles into specific parts of the body for therapeutic purposes, as in traditional Chinese medicine. Energy known as qi is believed to flow through channels (‘meridians’) linked to particular organs and functions; along these, needles are inserted at selected points to stimulate or depress the energy flow. Used in the treatment of a variety of diseases, for relief of pain or for production of anaesthesia.
acute injury refers to the first 24–48 h after an injury due to a traumatic episode, such as one sustained during a sporting activity.
adaptive behaviour a change in behaviour to successfully meet changes in environmental circumstances.
adaptive thermogenesis the thermic effect of factors such as cold, heat, fear, stress and various drugs that can increase the rate of energy expenditure above normal baseline levels.
addiction dependency on chemical substances such as drugs, alcohol and tobacco. Also more recently applied in exercise settings to a dependency on regular exercise. See also exercise dependence.
adduction movement of the arm inwards to the side of the body, of a leg inwards towards the other leg, of a thumb, finger or toe towards the middle of the hand or foot; adductor a muscle with this action. Opposite of abduction. See appendix 1.2 fig 3.
adenosine nucleotide consisting of a base, adenine, and a sugar, ribose.
adenosine mono-, di- and triphosphates (AMP, ADP, ATP) molecules in which one, two or three phosphate groups are combined with the ribose unit of adenosine. ATP is the key energy currency of every living cell. It is synthesized anaerobically by glycolysis and aerobically by oxidative phosphorylation, and is hydrolysed to ADP and a phosphate ion (‘inorganic phosphate’, Pi) by the ATPases of myosin, membrane pumps and all other energy-requiring systems. Accumulation of ADP, and even more so of AMP, signifies ATP depletion and stimulates ATP resynthesis. See also creatine kinase (fig), phosphocreatine.
adherence extent to which a person maintains a behavioural regimen, such as regular exercise. See also compliance.
adipose tissue specialized connective tissue where fat is stored (mainly subcutaneous; also around some organs, e.g. kidneys and heart); its cells, the adipocytes, are a major storage site for fat in the form of triacylglycerols (triglycerides) which can be mobilized by enzyme action (hormone-sensitive lipase) to provide fatty acids via the blood for energy metabolism, as in endurance exercise or in starvation. Also provides a protective and insulating layer. See also body composition, body fat, glucose, growth hormone.
adjective checklist in psychometrics, a list of adjectives that can be endorsed as applying or not applying to oneself or others.
adolescent athlete an athlete in the period between the onset of puberty and full maturity. This is the period of final bone growth and skeletal maturation, which increases the risk from contact injuries to the epiphyses (the ends of the long bones, not yet fused with the main shaft). The psychological changes that accompany the physical changes may result in problems with self-esteem, compliance and motivation.
adrenal glands endocrine glands sited above each kidney. The outermost region, the adrenal cortex, secretes steroid hormones: the glucocorticoids (principally cortisol), mineralocorticoids (principally aldosterone) and androgens in both male and female. The inner adrenal medulla secretes the catecholamines, mainly adrenaline and noradrenaline, under the control of the sympathetic nervous system. See also adrenocorticotrophic hormone (ACTH), hormones, steroids; appendix 5.
adrenaline (epinephrine) a catecholamine, one of the hormones secreted from the adrenal medulla into the blood stream, in response to stimulation by the sympathetic nervous system, increasing in circumstances requiring urgent and demanding action. Prepares the body for ‘fight or flight’ or for any other enhanced activity by increasing the heart rate and force, selectively increasing blood flow to muscle and mobilizing glucose from liver glycogen stores. Acts on adrenoceptors via the circulating blood, also as a neurotransmitter but, in mammals, only within the central nervous system.
adrenergic term used generically to describe nerves which liberate either adrenaline (epinephrine) or noradrenaline (norepinephrine) as a neurotransmitter from their endings; also in common usage in USA as an adjective for things associated with adrenaline or noradrenaline such as receptors. noradrenergic is sometimes used specifically to describe noradrenaline-releasing nerves. See also adrenoceptors.
adrenoceptors transmembrane proteins on cells that are activated by noradrenaline released at sympathetic nerve endings or by circulating catecholamines. There are three main types: alpha-1 (α1), alpha-2 (α2) and beta (β) which mediate responses by different cellular mechanisms and are activated preferentially by different agonists. Each type has three subtypes. All subtypes respond strongly to noradrenaline, β most strongly to adrenaline, and certain synthetic dugs can distinguish between α1 and α2. Such differences account, for example, for smooth muscle relaxation in some tissues (β-mediated vasodilatation in skeletal muscle; bronchodilation in the lungs) and vasoconstriction in others (α-mediated, in gut and skin) during heightened sympathetic activity. International agreement is for ‘adrenoceptor’ but the use of ‘adrenergic receptors’ is still common in the USA.
adrenocorticotrophic hormone (ACTH) a hormone secreted into the bloodstream by the anterior pituitary; acts on the adrenal cortex, promoting the secretion of corticosteroids. ACTH secretion is itself regulated by the ACTH-releasing hormone from the hypothalamus. This in turn is susceptible to many influences within central nervous system, taking part in responses to many types of injury or stress.
aerobic capacity maximum rate at which an animal or human subject can take up oxygen from the air; also known as maximal oxygen consumption (uptake) (
O2 max). Aerobic capacity of individual muscles is the maximum rate at which they can utilize oxygen. See also aerobic power.
aerobic endurance period for which aerobic work can be maintained by an individual; may vary from a few tens of seconds in a sedentary person and a few minutes in a sprint or power athlete, to more than 24 h in an ultra-marathoner.
aerobic exercise exercise furnished with energy by aerobic metabolism; regular repetition enhances the capacity of the cardiorespiratory system to deliver oxygen to muscles. Compare anaerobic exercise.
aerobic metabolism see glycolysis, oxidative phosphorylation.
aerobic power a term that is widely, but loosely, used as interchangeable with aerobic capacity, or 
O2 though the units for this are those of oxygen uptake rate, not power; ‘aerobic power’ would more properly refer to mechanical power output at 
O2.
aerobic threshold see metabolic and related thresholds.
aerobic training training aimed at enhancement of aerobic power or endurance; consists of intensive (for power) or sustained (for endurance) exercise below 
O2. See also target heart rate.
aetiology (etiology) strictly, the study of the causation of a condition but more commonly used to refer to causative factors themselves. aetiological factors those responsible for the origin and progress of a disorder or disease and ‘of unknown aetiology’ meaning that the cause is obscure.
affect in psychology, a general term for subjectively experienced feelings encompassing emotion and mood. adj affective. affective response subjectively experienced feeling in response to an environmental event. positive affect a general dimension of affect reflecting a state of enthusiasm and alertness. negative affect a general dimension of affect reflecting a state of distress, subsuming various negative moodstates including fear, anger, shame and guilt. See also circumplex model.
afferent means ‘going towards’. Describes nerves that carry impulses towards the central nervous system, or to relay stations outside it, from neural receptors (e.g. sensory nerves from the skin, those conveying proprioceptive information from muscles and joints or visceral afferents from internal organs). Also describes blood or lymph vessels in which flow is towards some point of reference, e.g. afferent arterioles to the glomeruli of the kidney. Opposite of efferent.
affordance a property of an object or a feature of the environment that offers an organism the opportunity to act in a particular way.
ageing and exercise certain risks, especially involving the cardiovascular system, increase with age. Ageing is associated with degenerative conditions; there is a reduction in bone density and deterioration of lung function, aerobic fitness and muscle strength. The benefits of activity in advancing years include a reduced incidence of heart disease, maintenance of bone mineral content (reducing fracture risk), muscle strength and balance (reducing falls) and an increased life expectancy. See also osteoporosis.
aggression behaviour with the intent of causing harm to another individual or group.
agonist an agent having a positive action. (1) In pharmacology, a chemical agent that causes a response by a cell when it binds selectively to a specific receptor. Usually refers to a drug which imitates the action of a hormone or neurotransmitter. (2) With reference to skeletal muscles, one, or a group, which is initiating or maintaining a positive action, e.g. the biceps when flexing the elbow. See also antagonist, reciprocal inhibition.
agreeableness one of the big five personality factors characterized by a tendency to be kind, generous, sympathetic and unselfish.
airway(s) the passage(s) from the mouth or nose via the pharynx, larynx, trachea and the branching bronchial tree to the alveoli of the lungs. Airway (singular) usually refers to the upper airway (upper respiratory tract) which may need to be cleared of inhaled or vomited material, e.g. before mouth-to-mouth (or -nose) resuscitation. Airways (plural) refers to the bronchial tree within the lungs, particularly in the context of chronic obstructive airways disease and asthma, when the smallest branches are narrowed. See appendix 1.3 fig 4.
alanine (Ala) an amino acid, one of the 20 building blocks of proteins in food and in the body. Not an ‘essential’ amino acid in the diet as it can be made in the body from other substances.
alcohol ethyl alcohol (ethanol) in alcoholic drinks is one of a group of organic compounds. The anxiety-reducing effects of alcohol can improve confidence and performance, particularly in sports where fine motor control is required, e.g. by snooker players or marksmen. In many sports, particularly team sports, alcohol intake is a part of the culture. Because of the well-known diuretic properties, athletes should be advised against alcohol consumption when fluid replacement is a priority, and alcohol can impair both performance and recovery after exercise. It is banned in some sports (e.g. motor racing, skiing).
aldosterone hormone secreted by the adrenal glands, at a rate regulated by the level of sodium in body fluids. Acts in the kidneys to enhance reabsorption of sodium, reducing its loss in the urine. Similar action on sweat glands reduces sodium loss when sweating rate is high. See also hormones; appendix 5.
Alexander Technique a form of psychophysical re-education. Based on the observation that unconscious habits, which disturb our postural reflexes, are associated with problems of health and performance, it promotes better co-ordination and control, aiming either to remove the cause of, or simply prevent, many forms of ill health, chronic pain, poor posture and inadequate performance. Developed in the late 1890s by an Australian actor who studied and improved his own vocal problems, the Technique is now widely recognized as a fundamental tool for establishing good co-ordination, balance and poise. It is valued by athletes as a way to improve performance and prevent or resolve injuries. It is taught on a one-to-one basis and teachers will usually have attended a three-year training course or its equivalent.
alexithymia a personality trait characterized by difficulty in recognizing or describing one’s emotions.
alimentary pertaining to the gut and its functions. alimentary tract the whole passage from mouth to anus, via the oesophagus, stomach, and intestines. alimentary system the tract and all that happens within it, including eating, digestion, absorption and excretion, and the movement of the contents by the intestinal smooth muscle. See fig appendix 1.4.
alkalosis condition following increase in pH of body fluids, from accumulation of base or depletion of acid. metabolic alkalosis is associated with loss of gastric acid with excessive vomiting, and respiratory alkalosis with excessive loss of carbon dioxide due to hyperventilation from any cause, including the physiological response to hypoxia at high altitude. In compensated alkalosis pH may be normal, with a low blood bicarbonate concentration (due to increased renal excretion) when the cause is respiratory, or with a raised blood carbon dioxide (due to hypoventilation) when the cause is metabolic. See also acid–base balance.
allergy an immune response induced by exposure to an allergen causing a harmful hypersensitivity reaction (allergic response) on subsequent exposure. See also immunity.
alpha-agonist in full alpha (α) adrenoceptor (or adrenergic) agonist a naturally occurring substance or a drug that acts specifically on cellular alpha-adrenoceptors. See also adrenaline, adrenoceptor, sympathetic nervous system.
alpha (α)-blocker a substance that interferes with the action at the adrenoceptor of an α-adrenergic agonist. In full alpha (α) adrenoceptor (or adrenergic) antagonist. Can be selective for alpha-1 (α1), alpha-2 (α2) or their further subtypes. See also adrenoceptor.
alpha (α)-ketoglutarate an intermediate in the Krebs cycle; may be depleted in the late stages of endurance exercise, suggesting potential utility as an anticatabolic agent.
alpha (α) motor neurons the final pathway for activation of skeletal muscles; neurons with cell bodies in the central nervous system (brain stem or spinal cord), and myelinated nerve fibres that terminate in motor endplates at neuromuscular junctions. See also gamma (motor) system, motor unit.
alpha (α) receptor see adrenoceptor.
alpha (α)-tocopherol the most biologically active form of vitamin E, which is the most important antioxidant in cell membranes. Its principal function is to stabilize the structural integrity of membranes by breaking the chain reaction of lipid peroxidation. Vitamin E is also essential for normal function of the immune system. See also reactive oxygen species, vitamins; appendix 4.2.
altitude the height above sea level. As atmospheric (barometric) pressure decreases progressively with increasing altitude, from the standard 1 atmosphere at sea level, the partial pressure of oxygen (PO2) decreases proportionately; the air still contains the same ∼21% of oxygen but there are fewer molecules of oxygen per unit volume. There is also a drop in temperature and humidity, but the essential problem for human life and activity is shortage of oxygen (hypoxia).
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