36 of the SEHS glossary’s terms, each with the part of the syllabus where you first meet it.
The lighter region in the centre of the A band containing only myosin filaments, which shortens and may disappear during contraction.
The percentage of the blood volume made up of red blood cells, typically higher in men than in women; raising it increases the oxygen-carrying capacity of the blood.
The iron-containing protein in red blood cells that binds reversibly with oxygen, loading it in the lungs and releasing it in the tissues; each molecule carries up to four oxygen molecules.
The number of times the heart beats per minute, measured in beats min⁻¹; typically 60–80 beats min⁻¹ at rest in an adult.
The difference between an individual's maximum heart rate and resting heart rate, representing the range of heart rate available for exercise.
The variation in the time interval between successive heartbeats, reflecting sympathetic and parasympathetic balance; a fall below an individual's normal resting value suggests incomplete recovery.
Flaps of tissue between the chambers of the heart and at the exits of the ventricles that open and close in response to pressure differences, so blood flows in one direction only.
The adaptations to repeated exercise in hot conditions over about 1–2 weeks, including earlier and greater sweating, more dilute sweat, larger plasma volume and lower heart rate and core temperature at a given workload.
A heat illness in which the cardiovascular system cannot meet the demands of muscles and skin, usually with dehydration, causing fatigue, dizziness, nausea and sometimes collapse, with core temperature usually below 40 °C.
A life-threatening failure of thermoregulation in which core temperature rises above about 40 °C with central nervous system dysfunction such as confusion or collapse; it needs immediate whole-body cooling.
The vertical distance between the point at which a projectile is released and the level at which it lands; releasing above the landing level lowers the best angle of release.
The proportion of the variation in a trait within a population that is explained by genetic differences between individuals; it describes a population, not one person.
A principle stating that choice reaction time increases as the number of possible stimulus–response alternatives increases, rising by a roughly constant amount each time the number of choices doubles.
Repeated bouts of high-intensity exercise, typically above 80% of maximum heart rate, lasting seconds to several minutes, separated by rest or low-intensity exercise.
A uniaxial synovial joint in which a convex surface fits into a concave one, allowing only flexion and extension, such as the elbow and knee.
The self-regulating processes that keep the body's internal environment relatively stable, within narrow limits, so that cells and organs function optimally despite internal and external changes.
A movement in the transverse plane that takes a limb, raised to the horizontal, backwards away from the midline, as in a discus wind-up; also called horizontal abduction.
A movement in the transverse plane that brings a limb, raised to the horizontal, forwards and across towards the midline, as in a chest press; also called horizontal adduction.
A chemical messenger released by an endocrine gland into the blood, which carries it to target cells elsewhere in the body, where it changes their activity.
Extension of a joint beyond the anatomical position, such as arching the lower back in a back walkover or swinging the arm behind the body.
A range of motion at several joints well beyond the normal range, which can help in sports such as gymnastics but may reduce joint stability and increase the risk of sprains and dislocations.
An abnormally high concentration of sodium in the blood plasma, above about 145 mmol per litre, usually caused by losing water with relatively little sodium, as in heavy sweating without drinking.
A resting blood pressure that is persistently at or above 140/90 mmHg in WHO and many European guidelines, or 130/80 mmHg in the 2017 American guideline; also called high blood pressure.
An abnormally high core body temperature resulting from heat production and gain exceeding heat loss; near about 40 °C during exercise it causes fatigue and risks heat illness.
A drink with a higher osmolarity than blood plasma, usually more than about 8% carbohydrate, which supplies energy but empties from the stomach and is absorbed more slowly.
An increase in the size of a muscle caused by an increase in the cross-sectional area of its fibres, mainly through the synthesis of more contractile proteins and myofibrils.
An abnormally low blood glucose concentration (below about 3.9 mmol per litre); in prolonged exercise it follows liver glycogen depletion and contributes to central fatigue.
The state of having less body water than normal, resulting from dehydration; it raises heart rate and core temperature during exercise.
An abnormally low concentration of sodium in the blood plasma, below 135 mmol per litre, most often caused in sport by drinking more hypotonic fluid than is lost during prolonged exercise.
A region at the base of the brain that links the nervous and endocrine systems; it controls body temperature, thirst and water balance, makes ADH and controls the pituitary gland.
A fall in core temperature below 35 °C, when heat loss exceeds heat production, causing shivering, then confusion, loss of coordination and, if it continues, unconsciousness and death.
A testable prediction of the relationship between variables, based on scientific theory, that the data of an investigation can support or fail to support.
A drink with a lower osmolarity than blood plasma, such as water or a dilute sports drink, which replaces fluid quickly but supplies little carbohydrate.
A shortage of oxygen reaching the body's tissues; at altitude it results from the lower partial pressure of oxygen, which reduces the saturation of haemoglobin with oxygen.
In catastrophe theory, the finding that after a performance collapse, arousal must fall well below the level at which the collapse occurred before performance can recover.