SEHS terms in Hydration and nutrition

The molecule left when ATP loses its terminal phosphate group and releases energy; it is rebuilt into ATP with inorganic phosphate using energy from the breakdown of fuels.

A molecule made of adenosine and three phosphate groups that is the immediate source of energy for muscle contraction; energy is released when the bond to its terminal phosphate is broken.

Describes a process that requires oxygen, such as the resynthesis of ATP by the oxidative system in the mitochondria.

A hormone secreted by the adrenal cortex that increases reabsorption of sodium, and excretion of potassium, by the kidneys, so that water follows by osmosis and blood volume is maintained.

The building block of proteins; an organic molecule containing a nitrogen-containing amino group and an acid group, of which twenty kinds are found in human proteins.

A condition in which the blood's haemoglobin concentration or number of red blood cells is below normal, reducing its ability to carry oxygen; iron deficiency is the most common cause.

Describes a process that takes place without oxygen, such as the resynthesis of ATP by the phosphagen and glycolytic systems in the sarcoplasm.

The process in the mitochondria that breaks fatty acids down into two-carbon units of acetyl coenzyme A, which then enter the Krebs cycle.

The total volume of water contained in the body, about 55–60% of body mass in adults, divided between the intracellular fluid and the extracellular fluid.

A mineral that gives bones and teeth their hardness and strength and, as calcium ions released from the sarcoplasmic reticulum, triggers muscle contraction; also needed for nerve transmission.

A macronutrient made of carbon, hydrogen and oxygen and built from sugar units; the main fuel for moderate and high-intensity exercise, stored in the body as glycogen.

A strategy of eating a very high-carbohydrate diet (about 10–12 g per kg of body mass per day) for 36–48 hours, with reduced training, to maximise muscle glycogen before an endurance event of over 90 minutes.

The gradual rise in heart rate and fall in stroke volume during prolonged steady-state submaximal exercise, with cardiac output roughly maintained, caused by fluid loss and a rising core temperature.

A maximal field test in which an individual runs as far as possible in 12 minutes; the distance covered is used to estimate VO₂ max.

The process in which lactate from muscle is carried in the blood to the liver, converted back to glucose and returned to the blood for use as a fuel.

The process of losing body water, so that losses such as sweat and urine exceed intake; the resulting state of reduced body water is called hypohydration.

A mineral that dissolves in body fluids to form charged ions, such as sodium, potassium, chloride, calcium and magnesium, which control fluid balance and nerve and muscle function.

A series of proteins on the inner membrane of the mitochondria that uses hydrogen from the Krebs cycle to resynthesise most of the ATP in aerobic metabolism, with oxygen accepting the hydrogen to form water.

The dietary energy left for the body's other functions after the energy cost of exercise is subtracted, per kilogram of fat-free mass per day: (energy intake − exercise energy expenditure) ÷ fat-free mass.

The relative contributions of the phosphagen, glycolytic and oxidative systems to ATP resynthesis, which change with the intensity and duration of an activity; all three systems contribute at all times.

A series of chemical reactions in the body that releases energy from a fuel and uses it to resynthesise ATP from ADP and inorganic phosphate: the phosphagen, glycolytic or oxidative system.

An amino acid the body cannot make in sufficient amounts, so it must be supplied by the diet; nine of the twenty amino acids are essential.

The state of normal body water content, within the small daily variation of about 1% of body mass found in a healthy person.

The volume of oxygen consumed after exercise above the resting level, used to return the body to its pre-exercise state; it has a fast and a slow component.

The fluid outside the cells, about one-third of total body water, made up mainly of interstitial fluid and blood plasma, in which sodium and chloride are the main ions.

The first 2–3 minutes of recovery, when oxygen consumption falls rapidly as phosphocreatine and ATP are resynthesised and the oxygen stores of myoglobin and blood are restored.

The mass of the body excluding all fat, made up of muscle, bone, organs, connective tissue and water; often called lean body mass.

A chain of carbon atoms with hydrogen atoms attached and an acid group at one end; saturated fatty acids have only single carbon–carbon bonds, unsaturated ones have one or more double bonds.

An earlier model describing three interrelated conditions in female athletes: low energy availability (with or without disordered eating), menstrual dysfunction and low bone mineral density.

A protein that stores iron in the body, mainly in the liver; the concentration of ferritin in the blood (serum ferritin) is used as a measure of iron stores.

The absence of digestive symptoms such as nausea, bloating, cramps and diarrhoea during exercise; it depends on what and when an athlete eats and drinks, exercise intensity and individual tolerance.

A monosaccharide that is the main carbohydrate in the blood and the form in which carbohydrate is taken up and used by cells for energy.

A ranking of carbohydrate foods from 0 to 100 by how much and how quickly they raise blood glucose compared with the same amount of glucose.

A branched polysaccharide made of many glucose units; the form in which carbohydrate is stored in skeletal muscle (about 500 g) and the liver (about 80 g).

The energy system that resynthesises ATP anaerobically by breaking down glucose or glycogen to pyruvate in the sarcoplasm, producing lactate and hydrogen ions when pyruvate forms faster than it is oxidised.

A test in which exercise intensity rises in stages until exhaustion, used to measure VO₂ max, the blood lactate response or maximum heart rate.

The community of trillions of microorganisms, mainly bacteria, living in the digestive tract, mostly in the large intestine, together with their genes; it affects nutrient availability, immunity and health.

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 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.

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 drink with a lower osmolarity than blood plasma, such as water or a dilute sports drink, which replaces fluid quickly but supplies little carbohydrate.

The fluid inside the body's cells, about two-thirds of total body water, in which potassium is the main positive ion.

A mineral that forms part of haemoglobin, myoglobin and some enzymes of the oxidative system, allowing oxygen to be transported, stored and used to resynthesise ATP aerobically.

A drink with about the same osmolarity as blood plasma, typically containing 6–8% carbohydrate and some sodium, which supplies both fluid and fuel and is absorbed quickly.

A cycle of reactions in the mitochondria that breaks down acetyl coenzyme A from carbohydrate, fat or protein, releasing carbon dioxide and hydrogen for the electron transport chain.

A compound formed from pyruvate when glycolysis is rapid; it is a fuel that is oxidised in muscle and the heart or converted to glucose in the liver, not the cause of muscle soreness.

The removal of lactate from the blood, mainly by oxidation in muscle fibres and the heart and by conversion to glucose in the liver through the Cori cycle.

The highest exercise intensity at which lactate is removed from the blood at the same rate as it is produced; above it, blood lactate concentration rises rapidly.

A macronutrient made mainly of carbon and hydrogen with little oxygen, insoluble in water; includes triglycerides (fats and oils), phospholipids and steroids, and provides about 37 kJ per gram.

A state in which energy intake is insufficient to cover the energy cost of exercise and still support the physiological functions needed for optimal health; below about 30 kcal per kg fat-free mass per day is clinically low.

A nutrient needed in large amounts (grams per day) that provides energy and materials for growth and repair; the three macronutrients are carbohydrates, proteins and lipids.

The highest constant exercise intensity at which blood lactate concentration stays stable over time, because lactate production and clearance are balanced.

A nutrient needed in small amounts (milligrams or micrograms per day), such as a vitamin or mineral, that provides no energy itself but is needed to release energy and to build and maintain tissues.

Structures inside cells, including muscle fibres, in which the Krebs cycle and electron transport chain use oxygen to resynthesise large amounts of ATP.

A single sugar unit, such as glucose, fructose or galactose; the simplest carbohydrate and the building block of disaccharides and polysaccharides.

A maximal field test in which participants run 20 m shuttles at a pace set by beeps that gets faster every minute; the level reached is used to estimate VO₂ max.

An iron-containing protein in muscle fibres that stores oxygen and transports it from the cell membrane to the mitochondria; type I fibres contain more of it than type II fibres.

The concentration of all dissolved particles in a solution, in milliosmoles per litre; normal plasma osmolarity is about 285. Osmolality is the same measure per kilogram of water.

The net movement of water molecules across a partially permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

The energy system that resynthesises ATP aerobically in the mitochondria by completely breaking down carbohydrate, fat and some protein, producing carbon dioxide and water; slow but with a very large capacity.

The difference between the oxygen needed to meet the energy demand of exercise aerobically and the oxygen actually consumed, mainly at the start of exercise; the shortfall is met by anaerobic systems.

The energy system that resynthesises ATP anaerobically from phosphocreatine in the sarcoplasm; it has the highest rate of ATP resynthesis but lasts only about 10 seconds at maximal intensity.

A high-energy phosphate compound stored in muscle that is broken down by creatine kinase to resynthesise ATP rapidly without oxygen, for about 10 seconds of maximal effort.

A carbohydrate made of many monosaccharide units joined in long chains, such as starch in plants and glycogen in animals; often called a complex carbohydrate.

A mineral that is the main positive ion inside cells; it is needed for nerve impulses, the contraction of skeletal and heart muscle, and fluid balance inside cells.

A meal eaten about 1–4 hours before exercise, high in carbohydrate and low in fat, fibre and protein, to top up liver glycogen and blood glucose without causing digestive discomfort.

A food component, usually a type of fibre, that is selectively used by beneficial gut microorganisms and so gives a health benefit, for example inulin in onions, garlic and oats.

Live microorganisms that, when taken in adequate amounts, give a health benefit to the person who takes them; found in some yoghurts, fermented foods and supplements.

A macronutrient made of chains of amino acids joined by peptide bonds; it provides material for the growth and repair of tissues and forms enzymes, some hormones and transport molecules.

A three-carbon molecule produced when glucose is broken down by glycolysis; it is oxidised in the mitochondria when oxygen is available or converted to lactate.

A syndrome of impaired physiological and psychological function, affecting health and performance, caused by problematic (prolonged or severe) low energy availability in athletes of any sex; also written RED-S.

The oxygen cost of running at a given submaximal speed, in mL kg⁻¹ min⁻¹ or mL kg⁻¹ km⁻¹; a more economical runner uses less oxygen at the same speed.

The cytoplasm of a muscle fibre: the fluid around the myofibrils in which phosphocreatine breakdown and glycolysis take place.

Fatty acids with fewer than six carbon atoms, such as acetate, propionate and butyrate, produced when gut bacteria ferment dietary fibre; they fuel colon cells and help regulate metabolism and inflammation.

The later, longer part of recovery, lasting minutes to hours, when oxygen is used to remove lactate and meet the raised cost of heart rate, ventilation, body temperature and hormones.

A mineral that is the main positive ion in extracellular fluid; it controls the volume of body water through osmosis and is needed for nerve impulses and muscle contraction.

A period of submaximal exercise during which oxygen consumption meets the oxygen demand of the activity, so heart rate and oxygen consumption stay roughly constant.

The volume of sweat lost per unit of time, usually in litres per hour, estimated from the change in body mass during exercise corrected for fluid drunk and urine passed.

The conscious desire to drink, generated by the hypothalamus in response to a rise in plasma osmolarity or a fall in blood volume.

A lipid made of one glycerol molecule joined to three fatty acids; the main form of fat in food and the body's largest energy store.

A numbered scale of urine shades used to estimate hydration status; pale straw shades indicate euhydration and darker shades indicate increasing hypohydration.

The density of a urine sample relative to pure water, used as an index of urine concentration; values above about 1.020 are commonly taken to indicate hypohydration.

An organic compound needed in small amounts that the body cannot make in sufficient quantities; vitamins regulate metabolic reactions, often as coenzymes, and support tissue synthesis.

The maximum rate at which the body can take in, transport and use oxygen during exercise with large muscle groups, in L min⁻¹ (absolute) or mL kg⁻¹ min⁻¹ (relative).