B
back injury injury to the back may affect the bones (vertebral column including the sacrum, also the ilium or the ribs), muscles and ligaments. Sport-related back injuries include fractures and damage from overuse, especially to the soft tissues. Mechanical and postural causes are common and a significant cause of morbidity in the general population. Damage may be prevented by attention to posture, flexibility, muscle strength and fitness. See also ankylosing spondylitis, intervertebral disc, spinal injury.
bacteria globally ubiquitous microscopic organisms, crucial to the ecosystem because of their metabolic turnover, for example, of nitrogen, carbon and sulphur. Bacteria were named from the Greek for rod, but only some (bacilli) are rod-shaped; others are spherical (cocci), curved or spiral (vibrios, spirilla, spirochaetes). Bacteria can be pathogenic to humans, other animals and plants, or non-pathogenic. Pathogens may be virulent and always cause infection whereas others, known as opportunists, usually only cause infection when the host defences are impaired. Non-pathogenic bacteria may become pathogenic if they move from their normal site, e.g. when normally beneficial (‘probiotic’) intestinal bacteria contaminate and infect a wound. Many bacteria have developed adaptations that allow them to exploit environments and survive unfriendly conditions – significantly, in modern times, enzymes that destroy antibiotics. Bacteria are classified and identified by features that include, as well as shape, staining characteristics (Gram positive or Gram negative) and whether or not they require oxygen (aerobic or anaerobic). sing bacterium. See also antibiotics.
Baker’s cyst an enlargement of the normally small bursa in the popliteal fossa, behind the knee. May cause pain and discomfort if large or inflamed (bursitis). Named after the 19th century British surgeon who first described it, William Morrant Baker.
balance stability of the body, attained in the case of humans and other terrestrial animals by a continuously active process involving vestibular, visual and proprioceptive inputs causing reflex postural muscle adjustment, so as to maintain the centre of gravity directly above the supporting base of the body. See also ear.
balanced diet a diet which provides adequate intake of both macronutrients and micronutrients, proper regulation of metabolic processes, and maintenance of an optimal body mass. In general, dietary guidelines for the average population are also applicable to athletes, but there are differences for athletes in the recommended intake of macronutrients, in terms of grams per day, grams per day per kg body mass or percentage of energy intake from each of the main foodstuffs. See also dietary reference values (DRV); appendix 4.
ballistic movement a movement, such as a long kick, in which a limb or part of a limb is initially accelerated forward by concentric muscle action, then swings pendulum-like through a passive (inertial or ‘ballistic’) phase of constant velocity, before being eccentrically decelerated.
bamboo spine see ankylosing spondylitis.
Bankart’s lesion damage to the capsule of the shoulder joint at the rim of the glenoid cavity of the scapula, caused by traumatic anterior dislocation of the shoulder joint and leading to recurrent dislocation with relatively minor injury. Named after the British orthopaedic surgeon who described the lesion in the 1920s. Bankart’s operation repairs the defect.
banned substance a substance which is on the list of banned doping classes and methods of the World Anti-Doping Agency (WADA) adopted (with some modifications) by the governing bodies of sport. See appendix 6.
baroreceptors sensors in the vascular system that respond to changes in pressure within blood vessels, generating afferent nerve impulses which elicit baroreflexes, causing appropriate corrections. The main arterial baroreceptors are in the wall of the carotid sinus on each side of the neck, where the common carotid artery divides into the internal and external carotids, and are responsible for regulation of arterial blood pressure, e.g. a rise in pressure elicits reflex reduction in peripheral resistance and/or cardiac output, via control centres in the brain stem.
barotrauma damage caused by change in pressure around the body (ambient pressure). Divers can be affected painfully by inequality between high ambient pressure at depth and that in closed internal air-containing spaces: the sinuses or the middle ear (aural barotrauma: inward bulging or at worst rupture of the eardrum, if the Eustachian tube is blocked). During surfacing the danger is pulmonary barotrauma: rupture of the lung surface by expanding air, with escape into the pleural cavity (pneumothorax) when surfacing without effective exhalation. See also decompression illness, diving.
basal metabolic rate (BMR) see metabolic rate.
beclomethasone an inhaled corticosteroid used in the treatment of asthma to reduce the inflammatory response, and used regularly as a ‘preventer’.
behaviour therapy form of psychotherapy designed to change maladaptive behaviour patterns using the principles of classical and operant conditioning. Also known as behaviour modification.
behavioural activation system (BAS) a neurobehavioural system thought to regulate positive affect and approach behaviour in response to incentives or rewards. Individuals vary in the sensitivity of the system and it is associated with the personality factor of extraversion. See also behavioural inhibition system (BIS).
behavioural analysis applied behaviour analysis application of the principles of operant conditioning to the treatment of behavioural problems. experimental analysis of behaviour application of the principles of operant conditioning to the study of behaviour. See also conditioning.
behavioural coaching application of the principles of operant conditioning and cognitive behaviour therapy to coaching, especially in sport or business.
behavioural inhibition system (BIS) a neurobehavioural system thought to regulate negative affect and avoidance behaviour in response to threats or punishment. Individuals vary in the sensitivity of the system and it is associated with the personality factor of neuroticism. See also behavioural activation system (BAS).
behavioural intention a person’s conscious or deliberate intention to engage in a behaviour.
behaviourism an approach to psychology which studies and interprets behaviour by objective observation of that behaviour without regard to any subjective mental processes such as ideas, emotions and will. Instead, all behaviour is held to be governed by conditioned responses.
bends an imprecise term traditionally used to describe some of the symptoms of decompression illness.
Bernouille principle the inverse relationship between pressure and velocity in a flowing fluid medium (liquid or gas).
beta-agonist in full beta (β)-adrenoceptor (-adrenergic) agonist a sympathomimetic drug that stimulates β-adrenoceptors. Subgroup β2 agonists are used in asthma, usually by inhalation, to dilate the airways by relaxing smooth muscle, acting as a ‘reliever’ of symptoms of wheeze, cough or breathlessness. In sport, some are allowed under doping regulations (salbutamol and terbutaline) while those with significant anabolic effects (clenbuterol) are prohibited. See also adrenaline, adrenoceptor, sympathetic nervous system; appendix 6.
beta-blocker in full beta (β)-adrenoreceptor (or adrenergic) antagonist a drug which blocks the stimulation of β1-adrenoceptors in the myocardium and at other sites; used primarily in the treatment of cardiovascular disease (ischaemic heart disease and hypertension) but also in the treatment of anxiety. Banned in sport due to the beneficial effect where fine hand movement and avoidance of tremor is important such as in archery, shooting and snooker. See also adrenaline, adrenoceptor, sympathetic nervous system; appendix 6.
beta-carotene precursor of vitamin A, usually ample in a normal diet, which is converted in the body to retinol. This and other carotenoids also function as antioxidants, protecting cells against oxidation damage. Beta-carotene supplements do not appear to have any ergogenic effect. Thus, it is recommended that this pro-vitamin is best obtained through the diet. See also vitamins; appendix 4.2.
beta-hydroxy-beta-methylbutyrate (HMB) one of the newest dietary supplements on the market, which is found naturally in small quantities in catfish, various citrus fruits and breast milk. HMB supplementation has been reported to be associated with enhanced gains in muscle mass and strength during resistance training. In addition to affecting protein synthesis, HMB is also claimed to stimulate fat oxidation. According to existing human data HMB is safe and well tolerated. See also ergogenic aids; appendix 4.4.
beta-receptor see adrenoceptor.
bicarbonate usually refers to sodium bicarbonate (as in ‘bicarbonate of soda’ or ‘baking soda’). In the body it is one of the most important extracellular buffers, and the bicarbonate level is an indirect measure of the acidity of the blood. The normal range for serum bicarbonate is 22–30 mmol.L−1. In sport, bicarbonate supplementation is used to enhance performance in athletic events conducted at near-maximum intensity for 1–7 minutes (400–1500 m running, 100–400 m swimming, kayaking, rowing and canoeing) as they may otherwise be limited by excess hydrogen ion accumulation. See also ergogenic aids; appendix 4.4.
biceps meaning ‘two-headed’. Usually refers to the biceps brachii, the muscle in the front of the upper arm; both heads have tendinous origins on the scapula, in front of and above the shoulder joint; their rounded bellies unite to form a single tendon which passes in front of the elbow to be inserted into the tuberosity of the radius. Its main actions are supination of the forearm and flexion of the elbow. The biceps femoris is one of the hamstring muscles in the back of the thigh. See appendix 1.2 fig 5A.
bicycle ergometer see cycle ergometer.
big five the widely accepted five fundamental personality factors comprising agreeableness, conscientiousness, extraversion, neuroticism and openness to experience.
bile secretion of the liver, variably stored in the gall bladder and discharged into the gut (duodenum). Contains the bile acids, important in the digestion and absorption of fats, and is the route for excretion of bile pigments (mainly bilirubin, from breakdown of the iron-containing pigments haemoglobin and myoglobin) and cholesterol.
binge-eating disorder an eating disorder characterized by a tendency to engage in episodes of binge eating. Similar to bulimia nervosa but without the accompanying compensatory behaviours such as self-induced vomiting and purging.
binge-purge syndrome see bulimia.
bioelectrical impedance analysis whole-body conductivity method for assessing body composition. A small alternating current flowing between two electrodes passes more rapidly through hydrated fat-free body tissues and extracellular water than through fat or bone because of the greater electrolyte content (lower electrical resistance) of the fat-free component. Impedance to electric current flow can be related to total body water content and in turn to fat-free mass, body density and percentage body fat.
biofeedback presentation of immediate visual or auditory feedback about normally unconscious body functions such as blood pressure, heart rate and muscle tension.
biomechanical analysis analysis of forces and motions of the human body. qualitative biomechanical analysis the analysis of forces and movements on (and by) the human body without regard to measurement or quantification. quantitative biomechanical analysis the analysis of forces and movements on (and by) the human body with emphasis on measurement and quantification.
biomechanics the understanding of forces and their effects on (and by) the human body and implements.
biopsy sample of tissue from a living subject. biopsy vt take such a sample.
bipolar construct a concept arranged along a single dimension with two opposite extremes, such as good–bad. Often used in self-report rating scales. For example, moodstates are often assessed by asking respondents to rate their mood on a set of bipolar scales such as composed–anxious, agreeable–hostile, elated–depressed.
blister a collection of fluid, usually serum, between the layers of the skin, causing an elevated lesion. Caused by friction, burns, local allergic responses, e.g. stings. Blisters are common with poor footwear or when exercise is of high intensity and long duration.
blood fluid circulating in the vascular system – the heart and blood vessels. The total volume is typically ∼5 litres in a man weighing 70 kg. The fluid plasma, carrying a great variety of substances, from simple inorganic ions to complex protein molecules, accounts for a little over half the blood volume and the cells (‘formed elements’) for the rest. See also body fluids, electrolytes, erythrocytes, extracellular fluids, leucocytes.
blood coagulation the process of clotting, which is one of the body’s natural means of stopping bleeding (haemostasis), activated by damage to the vessel lining. Results from a complex cascade reaction, dependent on the presence of ionized calcium and involving many ‘clotting factors’, some always present in the blood and some released from damaged tissue and platelets. The endproduct is a mesh of fibrin in which blood cells are trapped to form a solid mass. See also anticoagulant.
blood cells the cells circulating in the blood stream, accounting for a little less than half the total volume: erythrocytes (red blood cells) smaller but in far greater number than leucocytes (white blood cells) and platelets. See also haemopoiesis.
blood clotting see blood coagulation.
blood doping a procedure banned by the World Anti-Doping Agency (WADA): the administration of a blood transfusion to a sportsman or sportswoman in order to increase the oxygen-carrying capacity of the blood and as a result to improve performance. Most commonly, this involves removing up to a litre of the person’s blood and storing this while the body’s normal mechanisms replace the loss. At a later date, usually just prior to competition, the removed blood is transfused back into the circulation. Though banned, it is still used in some sports such as athletics and cycling as detection is difficult. The procedure is considered to be against the ethics of sport. Risks include renal damage, transmission of infection and circulatory overload.
blood flow quantity of blood flowing through a vessel, region or organ in unit time. Dependent on the arterial blood pressure and the resistance to flow in the local vascular bed, determined by the state of constriction/dilatation mainly of the arterioles, influenced in turn by chemical (local and hormonal) and neural (sympathetic) effects on the vascular smooth muscle.
blood gases normally refers to the oxygen and carbon dioxide that are dissolved in the arterial blood, following equilibration in the lungs between capillary blood and the gases in the alveoli. Measured as part of the assessment of lung function; expressed as partial pressures (or ‘tensions’) PO2 and PCO2. There is also a small amount of dissolved nitrogen, at a PN2 in equilibrium with alveolar nitrogen. See also hypoxia, hypercapnia, oxyhaemoglobin dissociation curve.
blood glucose (often loosely called ‘blood sugar’) is obtained by digestion of carbohydrates and by release from liver glycogen, and is taken up by the cells of the organs and tissues for use as an energy substrate. In healthy people, blood glucose concentration is homeo statically controlled within a fairly narrow range; maintenance of the normal level is critical for the function in particular of those tissues with an obligatory demand for glucose (brain, red blood cells, renal cortex, mammary gland and testis). Hormones involved include insulin, tending to lower blood concentration, and glucagon, glucocorticoids, adrenaline and growth hormone, tending to raise it. It seldom falls below about 5 mmol.L−1, even after prolonged fasting, and returns to this value within a couple of hours of the rise that follows a meal. When there is no uptake from the gut, about 8 g glucose per hour can be provided from the liver by breakdown of glycogen stores and by gluconeogenesis. During prolonged exercise glucose output from the liver closely matches the increased requirement, so that the blood concentration falls only when the hepatic glycogen store is depleted, close to exhaustion. See also hyperglycaemia, hypoglycaemia.
blood groups classification of types of human blood, originally for defining compatibility for transfusion. ABO groups the four main types, named according to the antigens on the individual’s red blood cells (RBC): A, B, AB (both) or O (none). (The donor’s blood cells will be catastrophically hydrolysed if the recipient’s plasma has antibodies to the donor cells’ antigens.) An individual’s blood plasma contains antibodies to whichever antigen(s) are not present on that person’s own red blood cells; for example, group O (no antigens) can donate to a recipient of any group, because the recipient’s plasma antigens can have no effect on the donor’s red cells, and group AB (no antibodies) can receive from a donor of any group. Rhesus (Rh) blood groups the majority of people (‘Rh positive’) have another red blood cell antigen. There is no antibody to this in anyone’s plasma, except when a person of the ‘Rh-negative’ minority has been exposed to the antigen. For example, a Rh-negative mother who has an Rh-positive baby raises antibodies that can harm a later Rh-positive fetus; likewise, a first transfusion with Rh-positive blood raises antibodies that react against a later one.
blood pressure the pressure exerted on the blood vessel walls. Normally refers to the arterial blood pressure, usually expressed in millimetres of mercury (mmHg) because of traditional sphygomanometry (which measures the height of a column of mercury sustained by the pressure in an inflated cuff around the arm that occludes the blood flow) but now more commonly measured by automated strain-gauge devices. Arterial blood pressure fluctuates with each heart beat between a maximum systolic pressure (SBP) during the ejection of blood from the heart and a minimum diastolic pressure (DBP) when the heart is relaxed with the aortic and pulmonary valves closed; the pulse pressure is the difference between them. When blood pressure is measured, values for both are quoted, e.g. 120/70 mmHg. May also be recorded directly from a cannula in an artery linked to a pressure transducer. mean (arterial) blood pressure (MBP) a mean value averaged over the cardiac cycle, derived from the arterial pulse pressure wave; typically closer to the diastolic than the systolic pressure such that MBP = DBP+(SBP−DBP)/3. See also hypertension, hypotension.
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