Glossary of terms

5-HT (5-Hydroxy tryptamine) -- A brain neurotransmitter; also known as serotonin.

5-hydroxytryptamine – see serotonin

absorption -- The transport of nutrients from the intestine into the blood or lymph system.

acclimatization -- Adaptation of the body to an environmental extreme (e.g. heat, cold, altitude).

acetyl CoA -- The major fuel for the oxidative processes in the body, being derived from the breakdown of glycogen, glucose and fatty acids. 

acid -- A substance which tends to lose a proton (hydrogen ion).

acid-base balance – The relative balance of acid and base products in the body.

acidosis -- A disturbance of the normal acid-base balance in which excess acids accumulate causing a fall in pH (e.g. when lactic acid accumulates in muscle and blood during high intensity exercise). 

ACSM -- American College of Sports Medicine.

ACTH (adrenocorticotrophic hormone) – Hormone secreted from anterior pituitary gland which stimulates release of cortisol from adrenal glands.

actin -- One of the major contractile proteins in muscle found in the thin filaments.

active transport -- The movement or transport across cell membranes by membrane carriers. An expenditure of energy (ATP) is required.

acute phase proteins -- Several proteins released from liver (e.g. C-reactive protein) and leukocytes that aid body’s response to injury or infection.

Adaptogen -- a name used for substances that help the body to adapt to stress situations

Adequate Intake (AI) -- Recommended dietary intake comparable to the RDA, but based on less scientific evidence. 

adipocyte -- An adipose tissue cell whose main function is to store triacylglycerol (fat).

adipose tissue – White fatty tissue that stores triacylglycerol. 

ADP ( adenosine diphosphate) – Breakdown product of ATP.

adrenaline -- A hormone secreted by the adrenal gland; it is a stimulant and prepares the body for "fight or flight." An important activator of fat and carbohydrate breakdown during exercise. Also known as epinephrine.

aerobic -- Occurring in the presence of free oxygen.

alanine -- A nonessential amino acid. 

alcohol -- A colorless liquid with depressant and intoxicating effects; ethyl alcohol or ethanol (C2H5OH) is the alcohol found in wines, spirits and beers. 

alimentary tract—see gastro-intestinal tract.

alkalinizer -- A group of substances with a buffering function (sodium bicarbonate, sodium citrate)

allosteric enzyme -- An enzyme which alters its three dimensional conformation as a result 

amenorrhoea - The absence of at least three successive menstrual cycles in females 

amino acid (AA) -- The chief structural molecule of protein, consisting of an amino group (NH2) and a carboxylic acid  group (CO2H) plus another so-called R-group that determines the amino acid’s properties. There are 20 different amino acids that can be used to make proteins.

ammonia (NH3) -- A metabolic by-product of the oxidation of amino acids; it may be transformed into urea for excretion from the body. 

AMP (adenosine monophosphate) -- product of the breakdown of adenosine diphosphate.

a-amylase or amylase -- a digestive enzyme found in saliva that begins the digestion of starches in the mouth (also called ptyalin). It catalyses the hydrolysis of starch by cleaving the a-1-4-glycosidic linkages between the component glucose molecules. Amylase is also present in pancreatic juice

amylase—see a-amylase

amylopectin -- A branched-chain starch. 

amylose -- A straight-chain starch that is more resistant to digestion compared to amylopectin. 

anabolism -- Constructive metabolism, the process whereby simple body compounds are formed into more complex ones. 

anaerobic -- Occurring in the absence of free oxygen.

androstenedione -- An androgenic steroid produced in the body that is converted to testosterone; marketed as a dietary supplement. 

anemia -- A condition defined by an abnormally low blood hemoglobin content resulting in a lowered oxygen carrying capacity

anion -- A negatively charged ion or electrolyte (e.g. chloride, Cl-; phosphate, H2PO4 2-)

anthropometry -- Use of body girths and diameters to evaluate body composition. 

antibody -- Soluble protein produced by B lymphocytes with antimicrobial effects.

antidiuretic hormone (ADH) – A hormone secreted by the posterior pituitary gland that influences water reabsorption by the kidneys

antioxidant -- molecules that can prevent or limit the actions of free radicals usually by removing their unpaired electron and thus converting them into something far less reactive. 

appetite -- A desire for food for the purpose of enjoyment that is developed through previous experience; believed to be controlled in humans by an appetite center in the hypothalamus. 

arginine -- An essential amino acid. 

arteriovenous (AV) – Refers to comparison of arterial and venous blood composition.

ascorbic acid -- Vitamin C; major role is a water soluble antioxidant.

aspartame -- An artificial sweetener made from amino acids. 

aspartates -- Salts of aspartic acid, an amino acid. 

ATP (adenosine triphosphate) -- A high energy compound that is the immediate source for muscular contraction and other energy requiring processes in the cell.

ATPase (adenosine triphosphatase) -- An enzyme that breaks down ATP to ADP and inorganic phosphate, releasing energy that can be used to fuel biological work.

Atrophy -- A wasting away, a diminution in the size of a cell, tissue, organ or part.

average daily metabolic rate (ADMR) -- The average energy expenditure over 24 hours.

base --      A substance which tends to donate an electron pair or co-ordinate an electron.

BCAA (branched chain amino acid) -- These are three essential amino acids that can be oxidized by muscle. Includes leucine, isoleucine and valine.

beta-carotene -- A precursor for vitamin A found in plants. Also called provitamin A.

beta-oxidation -- Process in the mitochondria whereby 2-carbon units (as acetyl groups) are 

bioavailability -- In relation to nutrients in food, the amount that may be absorbed into the body. 

bioelectrical impedance analysis (BIA) -- A method to calculate percentage of body fat by measuring electrical resistance due to the water content of the body. 

biopsy -- A small sample of tissue taken for analysis.

bm -- Body mass in kilograms (kg).

BMI (body mass index) – Body mass in kilograms divided by height in meters squared (kg/m2). An index used as a measure of obesity.

BMR (basal metabolic rate) -- Energy expenditure under basal, postabsorptive conditions representing the energy needed to maintain life under these basal conditions.

buffer        -- A substance which in solution prevents rapid changes in hydrogen ion concentration (pH).

bw -- Body weight.

caffeine -- A stimulant drug found in many food products such as coffee, tea, and cola drinks; stimulates the central nervous system and used as an ergogenic aid.

calorie (cal) -- Traditional unit of energy. One calorie expresses the quantity of energy (heat) needed to raise the temperature of 1 g (1 ml) of water 1oC (from 14.5oC to 15.5oC).

cAMP (cyclic adenosine monophosphate) -- An important intracellular messenger in the action of hormones.

capillary -- The smallest vessel in the cardiovascular system. Capillary walls are only cell thick and all exchanges of molecules between the blood and tissue fluid occur across the capillary wall.

carboloading – common practise of endurance athletes. Eating large quantities of carbohydrate in order to optimise body glycogen stores

carnitine -- A compound used to assist the transport of fatty acyl-CoA molecules from the muscle sarcoplasm across the mitochondrial inner membrane into the mitochondria for subsequent oxidation. 

catabolism -- Destructive metabolism whereby complex chemical compounds in the body are degraded to simpler ones (e.g. glycogen to glucose; proteins to amino acids). 

catalyst -- A substance that accelerates a chemical reaction, usually by temporarily combining with the substrates and lowering the activation energy, and is recovered unchanged at the end of the reaction (e.g. an enzyme).

cation -- A positively charged ion or electrolyte (e.g. sodium, Na+; calcium Ca2+).

CD (clusters of differentiation or cluster designators) -- Proteins expressed on cell surface of leukocytes (white blood cells) that can be used to identify different types of leukocyte or subsets of lymphocytes.

cell --        The smallest discrete living unit of the body.

cellulose -- A major component of plant cell walls; most abundant non starch polysaccharide. Cannot be digested by human digestive enzymes.

cereals, fruits, and vegetables in contrast to simple carbohydrates such as glucose, milk sugar and table sugar. 

CHO (carbohydrate) -- A compound composed of carbon, hydrogen and oxygen in ratio of 1:2:1 (i.e. CH2O). Carbohydrates include sugars, starches and dietary fibers.

choline – Can be found in phospholipids (phosphatidylcholine and sphingomyelin) and is a precursor for the neurotransmitter acetylcholine. 

chromium -- A trace element that plays a role in glucose metabolism.

chylomicrons -- A class of lipoproteins that transport exogenous (dietary) cholesterol and triglycerides from the small intestine to tissues after meals.

CK (creatine kinase) -- An enzyme that catalyses the transfer of phosphate from phosphocreatine to ADP to form ATP. Also known as creatine phosphokinase.

closed circuit spirometry -- A method to measure resting energy expenditure. The subject breathes through a mouthpiece into a closed system. The system (spirometer) is prefilled with 100% oxygen. The subjects rebreathes the same gas all the time and the resulting CO2 production is trapped by a filter. The volume in the system changes as oxygen is taken up and this change in volume is used to calculate oxygen uptake and energy expenditure.

CO2 (carbon dioxide) – Gas produced during oxidation of carbohydrates and fats.

CoA (coenzyme A) – A molecule that acts as a carrier for acyl or acetyl groups (A stands for acetylation).

coefficient of digestibility -- The percentage energy of food ingested that is actually digested, absorbed and available for metabolic processes in the body.

coenzyme -- Small molecules which are essential in stoichiometric amounts for the activity of some enzymes. Examples include nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD).

coenzyme Q10 -- A substance that assists in the oxidation of nutrients within cells to create energy. 

colon – The large intestine. This part of the intestine is mainly responsible for forming, storing and expelling faeces.

complex carbohydrates -- A term used to describe foods high in starch, such as bread, 

concentration gradient – Difference in concentration of a substance on either side of a membrane.            

conduction -- In relation to body temperature, the transfer of heat from one substance to another by direct contact. 

convection -- Heat exchange that occurs between a solid medium (e.g. the human body) and one that moves (e.g. air or water).

CoQ (Coenzyme Q , Q10 or ubiquinone) -- An electron carrier which mediates transfer of electrons from flavoprotein to cytochrome c in the electron transport chain that is located in the inner mitochondrial membrane.

CPT (carnitine palmitoyl transferase) – Enzyme that links the fatty acid palmitate to carnitine so that it can be transported across the inner mitochondrial membrane for subsequent oxidation.

creatine (Cr) -- Compound synthesized from amino acids that is the precursor of phosphocreatine an important anaerobic energy source for high intensity exercise.

creatinine -- A waste product of protein metabolism that is found in the urine. Can be measured to assess overall kidney function. An abnormally elevated blood creatinine level is seen in those individuals with kidney insufficiency and kidney failure.

crucial intermediates that might otherwise become depleted (e.g. the formation of oxaloacetate 

cutaneous -- In the skin.

cytochrome -- An iron-containing heme protein of the mitochondrial electron transport chain that can be alternately oxidised and reduced.

cytokine -- Protein released from cells that acts as a chemical messenger by binding to receptors on other cells. Cytokines include interleukins (IL), Tumor necrosis factors (TNF), colony stimulating factors (CSF) and interferons (IFN).

cytotoxic -- Ability to kill other cells (e.g. those infected with a virus).

daily reference intake (DRI) -- The term used to encompass the latest nutrient recommendations by the Food and Nutrition Board of the National Academy of Sciences.

deamination -- Reaction involving the loss of an amino (NH2) group.

decarboxylation -- Reaction involving the loss of a CO2 group.

dehydration -- Reaction involving the loss of a water molecule or loss of body water.

dehydroepiandrosterone (DHEA) -- is an androgen steroid that is sold as a nutrition supplement, often referred to as “youth hormone”.

denaturation -- Alteration of the physical properties and 3-dimensional structure of a protein by a chemical or physical treatment that does not disrupt the primary structure, but generally results in the inactivation of the protein (e.g. the inactivation of enzyme activity by the addition of a strong acid).

DEXA (or DXA) -- Dual energy X-ray absorptiometry (DXA or DEXA) is a high-tech technique which has become the clinical standard to measure bone density. The principle is based on absorption of low-energy X-rays. 

DHEA        (dehydroepiandrosterone) -- A steroid hormone produced endogenously by the adrenal gland. May be marketed as a nutritional sports ergogenic as derived from herbal precursors.

diarrhea -- Frequent passage of a watery fecal discharge due to a gastrointestinal disturbance or infection. 

diastolic -- The time, in between ventricular contractions (systole), at which ventricular filling occurs.

diet-induced thermogenesis (DIT) -- The energy needed for the digestion, assimilation and metabolism food that is consumed (also referred to as Thermic Effect of Food; TEF).

diffusion -- The movement of molecules from a region of high concentration to one of low concentration, brought about by their kinetic energy.

digestion -- The process of breaking down food to its smallest components so it can be absorbed in the intestine.

disaccharide -- Sugars that yield two monosaccharides on hydrolysis; sucrose is the most common and is composed of glucose and fructose. 

diuretics -- Drugs that act on the kidney to promote urine formation.

dm (dry matter or dry material) -- Usually refers to tissue weight after removal of water.

DNA (deoxyribonucleic acid) -- The compound that forms genes (i.e. the genetic material).

Dopamine -- A catecholamine neurotransmitter and hormone formed by decarboxylation of dehydroxyphenylalanine (dopa). A precursor of adrenaline and noradrenaline.

Douglas bag -- A plastic bag to collect expired gases for a certain period of time and to measure the volume, the O2 concentration and the CO2 concentration of this gas. From the measurements of inhaled and exhaled air, energy expenditure and substrate utilization can be calculated. These bags (Douglas bags) are named after British scientist Claude Douglas (1882-1963) who was the first to use this method to measure gas exchange in humans.

DRV (daily reference value) -- Recommended daily intakes for the macronutrients (carbohydrate, fat and protein) as well as cholesterol, sodium and potassium. On a food label, the DRV is based on a 2,000 kcal (8.3 MJ) diet.

duodenum -- The first 20-30 cm of the small intestine

DV (daily value) -- A term used in food labeling that is based on a daily energy intake of 2,000 kcal (8.3 MJ) and for the food labeled, gives the percentage of the RDI and the DRV recommended for healthy people in the USA. 

eating disorder -- A psychological disorder centering on the avoidance or purging of food, such as anorexia nervosa and bulimia nervosa.

eccentric exercise -- Types of exercise which involve lengthening of the muscle during activation which can cause damage to some of the myofibers. Types of exercise that have a significant eccentric component include downhill running, bench stepping and lowering of weights.

economy – Oxygen uptake needed to exercise at a certain work load or speed 

eicosanolds -- Derivatives of fatty acids in the body that act as cell-cell signaling molecules; they include prostaglandins, thromboxanes and leukotrienes. 

electrolyte -- A substance which, when dissolved in water, conducts an electric current. Electrolytes, which include acids, bases and salts, usually dissociate into ions carrying either a positive charge (cation) or a negative charge (anion).

electron transport chain (ETC) -- Proteins located on the inner mitochondrial membrane that transfer electrons from reduced coenzymes NADH and FADH2 to oxygen and allow protons to be pumped into the space between the inner and outer mitochondrial membranes. The flow of H+ ions (protons) back into the inner mitochondrial matrix through the ATP synthase complex is used to drive ATP synthesis.

endocrine -- Ductless glands that secrete hormones into the blood.

endogenous carbohydrate oxidation – Oxidation of carbohydrates from body stores (muscle and liver glycogen).

energy -- The ability to perform work. Energy exists in various forms including: mechanical, heat and chemical energy.

energy balance -- The balance between energy intake and energy expenditure.

energy expenditure (EE) -- The energy expended per unit of time to produce power.

energy expenditure for activity (EEA) – The energy cost associated with physical acrivity (exercise).

enzyme -- A protein with specific catalytic activity. They are designated by the suffix "-ase", frequently attached to the type of reaction catalysed. Virtually all metabolic reactions in the body are dependent on and controlled by enzymes.

Ephedrine -- An alpha- and beta-adrenergic agonist that may also enhance release of norepinephrine. It has been used in the treatment of several disorders including asthma, heart failure, rhinitis, and urinary incontinence, and for its central nervous system stimulatory effects in the treatment of narcolepsy and depression. Ephedrine is on the IOC list of banned substances. 

epinephrine -- A hormone secreted by the adrenal gland; it is a stimulant and prepares the body for "fight or flight." An important activator of fat and carbohydrate breakdown during exercise. Also known as adrenaline. 

ergogenic – performance enhancing

ergogenic aids – Substances that improve exercise performance and are used in attempts to increase athletic or physical performance capacity. 

ergolytic -- A substance that may lead to decreased exercise capacity or physical performance. 

ergolytic – impairs performance

erythrocyte -- Red blood cell that contains hemoglobin and transports oxygen.

essential amino acids -- Those amino acids that must be obtained in the diet and cannot be synthesized in the body. Also known as indispensable amino acids.

essential fatty acids -- Those unsaturated fatty acids that cannot be synthesized in the body and must be obtained in the diet (e.g. linoleic acid and linolenic acid).

estimated Average Requirement (EAR) -- Nutrient intake value estimated to meet the requirements of half the healthy individuals in a group. 

estimated mineral requirement (EMR) -- Part of the RDA pertaining to the minimal daily requirement for sodium, chloride, and potassium. 

estimated safe and adequate daily dietary intakes (ESADDI) -- Daily allowances for selected nutrients that are based upon available scientific evidence to be safe and adequate to meet human needs. 

estradiol – A hormone  synthesised mainly in the ovary, but also in the placenta, testis and possibly adrenal cortex.

euhydration -- Normal state of body hydration (water content).

eumenorrhoea -- Occurrence of normal menstrual cycles.

evaporation -- The loss of water that occurs when water on a surface changes from a liquid to a gas.

excretion -- The removal of metabolic wastes.

exogenous carbohydrate oxidation – Oxidation of carbohydrates that have been ingested or infused but are not from body stores.

extracellular fluid (ECF) -- Body fluid that is located outside the cells including the blood plasma, interstitial fluid, cerebrospinal, synovial and ocular fluids. 

fasting -- Starvation; abstinence from eating that may be partial or complete.

fatty acid binding protein (FABP) -- A protein found in liver and muscle that binds fatty acids in order to maintain a low intracelleluar free fatty acid concentration.

FDA -- Food and drug administration (USA).

ferritin -- A protein that is used to store iron. Ferritin is mostly found in the liver, spleen and bone marrow. Soluble ferritin is released from cells into the blood plasma in direct proportion to cellular ferritin content. Hence the serum ferritin concentration can be used to indicate the status of the body’s iron stores

FFA (free fatty acid) -- A fatty acid that is not esterified to glycerol or any other molecule. 

FFM (fat-free mass) – Lean mass of a tissue or the whole body.

fiber – Indigestible carbohydrates.

fish oil -- Oils high in unsaturated fats extracted from the bodies of fish or fish parts, especially the livers. The oils are used as dietary supplements. 

flux -- The rate of flow through a metabolic pathway.

food diary -- A written record of sequential food intake over a period of time. Details associated with the food intake are often recorded as well.

Fractional breakdown rate (FBR) -- The relative rate of protein breakdown which is calculated from measurements using isotopic tracers. 

Fractional synthesis rate (FSR) -- The relative rate of protein synthesis which is calculated from measurements using isotopic tracers. 

free radical -- An atom or molecule that possess at least one unpaired electron in its outer orbit. The free radicals the superoxide (.O2-), hydroxyl (.OH) and nitric oxide radical (.NO). They are highly reactive and may cause damage to lipid membranes causing membrane instability and increased permeability. Free radicals can also cause oxidative damage to proteins including enzymes and damage to DNA.

from pyruvate by pyruvate carboxylase).

fTRP – Free tryptophan (used to distinguish from tryptophan that is bound to protein). Tryptophan is an essential amino acid and a precursor of the neurotransmitter serotonin in the brain.

gastric emptying -- The rate at which substances (food and fluids) leave the stomach into the small intestine. A high gastric emptying rate is advisable for sports drinks.

gastro-intestinal tract (GI-tract) -- Gastro-intestinal system or alimentary tract. The main sites in the body used for digestion and absorption of nutrients. It consists of the mouth, esophagus, stomach, small intestine, large intestine, rectum and anus.

gene -- A specific sequence in DNA that codes for a particular protein. Genes are located on the chromosomes; each gene is found in a definite position (locus)

genotype -- The genetic composition or assortment of genes that together with environmental influences determines the appearance or phenotype of an individual.

ginseng -- A root found in Asia and the United States, although the Oriental variety is more easily obtainable. Ginseng has been a popular nutritional supplement and medication in the Orient for centuries. 

gluconeogenesis -- The synthesis of glucose from non-carbohydrate precursors such as glycerol, ketoacids or amino acids.

GLUT -- Glucose (or other monosaccharide) transporter found in cell membranes, including 

GLUT-4 -- Isoform of the glucose transporter found in sarcolemma of muscle fibers.

GLUT-5 -- Isoform of the glucose transporter found in the epithelial cell membranes of the gut.

glutamate – amino acid which acts as a neurotransmitter and a precursor of neurotransmitter

glutamine -- One of the 20 amino acids commonly found (and directly coded for) in proteins.

glycemic index – (GI) refers to the increase in blood glucose and insulin response to a meal. The GI of a food is expressed against a reference food, usually glucose. 

glycemic load – (GL) refers to the increase in blood glucose and insulin response to a meal (like glycemic index) but does take into account the amount of that food that  is normally consumed.

glycerol – 3 carbon structure which is backbone structure of triglycerides

glycogen -- Polymer of glucose used as storage form of carbohydrate in the liver and muscles.

glycogenolysis -- The breakdown of glycogen into glucose-1-phosphate by the action of phosphorylase.

glycolysis -- The sequence of reactions which converts glucose (or glycogen) to pyruvate.

H+ -- Hydrogen ion or proton

H2O2 -- Hydrogen peroxide.

half-life -- Time in which half the quantity or concentration of a substance is eliminated or removed.

HCl – Hydrochloric acid; part of gastric digestive juices.

HCO3- -- Bicarbonate ion: the principal extracellular buffer.

heat stroke -- Elevated body temperature of 41° C (105.8° F) or greater caused by exposure to excessive heat or high levels of heat production and diminished heat loss. May result in tissue damage and is potentially fatal.

heat syncope -- Fainting caused by excessive heat exposure. 

helix -- A spiral having a uniform diameter and a periodic spacing between the coils; a common secondary structure of proteins and DNA.

hematocrit -- Proportion of the blood volume that is occupied by the cellular elements (red cells, white cells and platelets). Also known as the packed cell volume.

heme -- Molecular ring structure that is incorporated in the hemoglobin molecule enabling this protein to carry oxygen.

hemodilution -- A thinning of the blood due to an expansion of the without an equivalent rise in red blood cells.

hemoglobin -- The red, iron-containing respiratory pigment found in red blood cells. Hemoglobin is important in the transport of respiratory gases and in the regulation of blood pH.

hemolysis -- Destruction of red blood cells within the circulation.

hemorrhage -- Damage to blood vessel walls resulting in bleeding.

hepatic glucose output  -- Liver glucose output. The glucose that is released from the liver as a result of glycogenolysis or gluconeogenesis.

hexokinase (HK) -- Enzyme that catalyses the phosphorylation of glucose to form glucose-6-phosphate.

HMB – see beta-hydroxy beta methylbutyrate

HMB (beta-hydroxy-beta-methylbutyrate) -- A metabolic by-product of the amino acid 

homeostasis -- The tendency to maintain uniformity or stability of the internal environment of the cell or of the body.

hormone -- An organic chemical produced in cells of one part of the body (usually an endocrine gland) that diffuses or is transported by the blood circulation to cells in other parts of the body, where it regulates and co-ordinates their activities.

hormone sensitive lipase: Enzyme that splits triacylglycerols into fatty acids and glycerol. it is regulated by hormones (mainly by adrenaline and insulin)

humoral -- Fluid borne.

hydration -- A reaction involving the incorporation of a molecule of water into a compound or  a term relating to the state of the body water content.

hydrogen bond -- A weak intermolecular or intramolecular attraction resulting from the interaction of a hydrogen atom and an electronegative atom possessing a lone pair of electrons (e.g. oxygen or nitrogen). Hydrogen bonding is important in DNA, RNA and is responsible for much of the tertiary structure of proteins.               

hydrolysis -- A reaction in which an organic compound is split by interaction with water into simpler compounds.

hydroxylation -- A reaction involving the addition of a hydroxyl (OH) group to a molecule.

hyperhydration -- Increased body water content above normal level.

hyperthermia -- Elevated body temperature (>37°C).

hypertonic -- Having a higher concentration of dissolved particles (osmolality) than that of another solution with which it is being compared (usually blood plasma which has an osmolality of 290 mOsm/kg).

hyperventilation -- A state in which there is an increased amount of air entering the pulmonary alveoli (increased alveolar ventilation), resulting in reduction of carbon dioxide tension and eventually leading to alkalosis. 

hyponatremia -- Below normal serum sodium concentration (< 140 mmol/l).

hypothalamus -- Region at base of brain responsible for integration of sensory input and effector responses in regulation of body temperature. Also contains centers for control of hunger, appetite and thirst.

hypothermia -- Lower than normal body temperature.

hypotonic -- Having a lower concentration of dissolved particles (osmolality) than that of another solution with which it is being compared (usually blood plasma which has an osmolality of 290 mOsm/kg).

hypovolemia -- Reduced blood volume.

Hz -- Unit of frequency: cycles per second.

Ig (immunoglobulin) -- Same as antibody.

IGF --         Insulin-like growth factor.

immunodepression -- Lowered functional activity of the immune system.

IMTG (intramuscular triacylglycerol) – Storage form of fat found in muscle fibers.

in vitro -- Within a glass, observable in a test tube, in an artificial environment. 

in vivo -- Within the living body.

indirect calorimetry -- A method to measure energy expenditure and substrate utilization on the basis of gas exchange measurements. The term indirect refers to the measurement of O2 uptake and CO2 production rather than the direct measurement of heat transfer. 

inflammation -- Body’s response to injury which includes redness (increased blood flow) and swelling (edema) due to increased capillary permeability.

inhibition or activation of its activity

insoluble fiber -- Fiber that does not dissolve in water.

insomnia -- Difficulty with sleeping.

insulin -- A hormone secreted by the pancreas involved in carbohydrate metabolism and in particular the control of the blood glucose concentration. 

interleukin -- Type of cytokine produced by leukocytes and some other tissues; acts as a chemical messenger rather like a hormone but usually with localized effects.

interstitial -- Fluid filled spaces that lie between cells.

IOC -- International Olympic Committee

ion -- Any atom or molecule which has an electrical charge due to loss or gain of valency (outer shell) electrons. Ions may carry a positive charge (cation) or a negative charge (anion).

ischemia -- Reduced blood supply to a tissue or organ.

isotonic -- Having the same concentration of dissolved particles (osmolality) than that of another solution with which it is being compared (usually blood plasma which has an osmolality of 290 mOsm/kg).

isotope -- One of a set of chemically identical species of atom which have the same atomic number but different mass numbers (e.g. 12-,13- and 14-isotopes of carbon whose atomic number is 12).

IU -- International units.

jejunum -- The middle and longest part of the small intestine where a lot of the absorption of nutrients takes place. The jejunum is approximately 1-2 m long.

joule (J) -- Unit of energy according to the Systeme Internationale. One Joule is the amount of energy needed to move a mass of 1 g at a velocity of 1 m/s.

keto-acids -- An acid containing a ketone group (-CO-) in addition to the acid group(s)


ketogenesis -- The synthesis of ketones such as acetoacetate, 3-hydroxybutyrate and acetone.

ketone bodies -- Acidic organic compounds produced during the incomplete oxidation of fatty acids in the liver.  Contain a carboxyl group (-COOH) and a ketone group (-C=O). Examples include acetoacetate and 3-hydroxybutyrate.

kinase       -- An enzyme that regulates a phosphorylation-dephosphorylation reaction (i.e. the addition or removal of a phosphate group). This is one important way in which enzyme activity can be regulated.

kJ (kilojoule) -- Unit of energy (kJ = 103J).

lactase      -- Enzyme responsible for the splitting of lactose into galactose and glucose

lactate dehydrogenase (LDH) -- enzyme that catalyses the reversible reduction of pyruvate to lactate.         

lactic acid – Metabolic end product of anaerobic glycolysis.

lactose      -- milksugar, a disaccharide linking a molecule of glucose and a molecule of galactose

lactovegetarian -- A vegetarian who includes milk products in the diet. 

LDL (low density lipoproteins) – A protein-lipid complex in the blood plasma that facilitates the transport of triacylglycerols, cholesterol, and phospholipids.

LDL-C cholesterol (low-density lipoprotein cholesterol) – A way in which cholesterol is transported in the blood. High blood levels are associated with increased incidence of coronary heart disease. 

Lean body mass -- All parts of the body excluding fat

lecithin (phosphatidyl choline) -- a phospholipid that occurs naturally in a variety of food items (beans, eggs, wheat germ). 

leukocyte -- White blood cell.  Important in inflammation and immune defense.

leukocytosis -- Increased number of leukocytes in the circulation.

lipase -- An enzyme that catalyses the hydrolysis of triacylglycerols into fatty acids and glycerol.

lipid --      A compound composed of carbon, hydrogen and oxygen and sometimes other elements. Lipids dissolve in organic solvents but not in water and include triacylglycerol, cholesterol and phospholipids           . Lipids are commonly called fats.

lipid peroxidation -- Oxidation of fatty acids in lipid structures (e.g. membranes) caused by the actions of free radicals.

lipolysis -- The breakdown of triacylglycerols into fatty acids and glycerol.

long chain fatty acid (LCFA) -- Part of triacylglycerols; hydrocarbon chains with 12 or more carbon atoms; most abundant type of fatty acids; palmitic acid and oleic acid are most abundant long chain fatty acids in humans.

long chain triacylglycerols -- Triacylglycerol consisting of glycerol and three long fatty acids

lymphocyte -- Type of white blood cell important in the acquired immune response. Include both T cells and B cells; the latter produce antibodies.

macromineral -- Those dietary elements essential to life processes that each constitute at least 0.01% of total body mass. There are seven macrominerals (potassium, sodium, chloride, calcium, magnesium, phosphorus and sulfur).

macronutrients -- Nutrients ingested in relatively large amounts (carbohydrate, fat, protein and water).

macrophage or monocyte -- Type of white blood cell that can ingest and destroy foreign material and initiate the acquired immune response.

maltodextrin -- A glucose polymer (commonly containing 6-12 glucose molecules) that exerts lesser osmotic effects compared with glucose and is used in a variety of sports drinks as the main source of carbohydrate. 

maltose -- A disaccharide that yields two molecules of glucose upon hydrolysis.

may be hydrolyzed by dilute acids outside of the body. Not hydrolyzed in the body. 

medium chain fatty acid (MCFA) -- A fatty acid with 8 or 10 carbon atoms.

medium-chain triacylglycerol (MCT) – Triacylglycerol (triglyceride) containing fatty acids with hydrocarbon chain lengths of 6-12 carbons. 

menstruation -- Monthly bleeding and discharge of the outer uterine wall in healthy females.

metabolic acidosis: A metabolic derangement of acid-base balance where the blood pH is abnormally low.

metabolite -- A product of a metabolic reaction.

METS (metabolic equivalents) -- A measurement of energy expenditure expressed as multiples of the resting metabolic rate; one MET equals approximately an oxygen uptake rate of 3.5 ml O2/kg body mass/minute. 

micromineral or trace element -- Those dietary elements essential to life processes that each comprise less than 0.001% of total body mass and are needed in quantities of less than 100 mg per day. There are 14 trace elements including iron, zinc, copper, chromium and selenium.

micronutrients -- These are the organic vitamins and inorganic minerals that must be consumed in relatively small amounts in the diet in order to maintain health.

mineral -- An inorganic element found in nature though the term is usually reserved for those elements that are solid. In nutrition, the term mineral is usually used to classify those dietary elements essential to life processes. Examples are calcium and iron.

mitochondrial matrix -- The substance occupying the space enclosed by the inner membrane of a mitochondrion; it contains enzymes, filaments of DNA, ribosomes, granules, and inclusions of protein crystals, glycogen, and lipid.

mitochondrion -- Oval or spherical organelle containing the enzymes of the tricarboxylic acid cycle and electron transport chain. Site of oxidative phosphorylation (resynthesis of ATP involving the use of oxygen).

mole -- The amount of a chemical compound whose mass in grams is equivalent to its molecular weight, the sum of the atomic weights of its constituent atoms.

molecule -- An aggregation of at least two atoms of the same or different elements held together by special forces (covalent bonds) and having a precise chemical formula (e.g. O2, C6H6O6).

monosaccharide -- A simple sugar that cannot be hydrolysed to smaller units (e.g. glucose, fructose, galactose).

motility -- The movement of food through the gastro-intestinal tract by coordinated muscular contractions of the intestine. 

motor unit -- All the muscle fibers supplied by a single motor neurone.

MRI (magnetic resonance imaging) – An imaging technique that generates pictures of body tissues and compartments. The results are somewhat similar to those obtained by a CT scan but with MRI electromagnetic radiation is used rather than ionising radiation.

mucosa -- Layer of cells lining the mouth, nasal passages, airways, gut etc which present a barrier to pathogen entry into the body.

myoglobin -- A protein that functions as an intracellular respiratory pigment that is capable of binding oxygen and only releasing it at very low partial pressures.

nandrolone -- A steroid with androgenic and anabolic properties.

NCAA        -- National Collegiate Athletic Association (USA)

NEFA         -- Non-esterified fatty acid. Same as free fatty acid (FFA).

neurotransmitters -- endogenous signalling molecules which transfer information from one nerve ending to the next.

neutrophil -- Type of white blood cell that can ingest and destroy foreign material; very important as a first line of defense against bacteria.

NH2 --        Amino group.

NH4+ -- Ammonium ion.

NK --          Natural killer (cell). A type of lymphocyte important in eliminating viral infections and preventing cancer.

NO -- Nitric oxide

norepinephrine -- Catecholamine neurohormone, the neurotransmitter of most of the sympathetic nervous system (of so called adrenergic neurons)

nutraceutical -- A nutrient that may function as a pharmaceutical (drug) when taken in certain quantities. 

nutrient -- Substances found in food that provide energy or promote growth and repair of tissues. 

nutrition density -- Amount of essential nutrients expressed per unit of energy in the food.

O2 -- Oxygen molecule

oligosaccharide -- A saccharide of a small number of component sugars, either O or N linked to the next sugar.

osmolality -- A measure of the total dissolved particle concentration; units are osmoles/kg.

osmolarity -- A measure of the total concentration of a solution; the number of moles of solute per liter of solvent typically expressed in mOsm/L.

osmoreceptors -- Sensory cells in the hypothalamus capable of detecting changes in osmolality of the blood.

osmosis -- The diffusion of water molecules from the lesser to the greater concentration of solute (dissolved substance) when two solutions are separated by a membrane that selectively prevents the passage of solute molecules but is permeable to water molecules.

osteoblasts -- Cells responsible for mineralization of bone.

osteoclasts -- Cells responsible for breakdown (demineralization) of bone.

osteoporosis -- A weakening of the bone structure that occurs when the rate of demineralization exceeds the rate of bone formation.

ovolactovegetarian -- A vegetarian who also consumes eggs and milk products.

ovulation -- Monthly release of an ova (egg) from the ovaries in females.

oxidation -- A reaction involving the loss of electrons from an atom. It is always accompanied by a reduction. For example pyruvate is reduced by NADH to form lactate. In the reverse reaction lactate is oxidised by NAD+ when pyruvate is reformed.

oxidative phosphorylation -- Resynthesis of ATP involving the use of oxygen.

pancreas -- An organ located below and behind the stomach. It secretes insulin and glcuogon (involved in plasma glucose regulation) and pancreatic enzymes involved in the digestion of fats and protein in the small intestine.

pancreatic duct -- The connecting tube between pancreas and duodenum through which pancreatic juice is transported into the duodenum.

pancreatic juice -- The secretions of the pancreas that are transported by the pancreatic duct to the duodenum. Pancreatic juice contains bicarbonate, and the digestive enzymes amylase, lipase and trypsin.

parathyroid hormone (PTH) – Hormone secreted from the parathyroid glands and involved in regulation of the blood plasma calcium ion concentration.

pathogen -- Micro-organism that can cause symptoms of disease.

PCr -- Phosphocreatine or creatine phosphate. An important energy source in very high intensity exercise.

PDH complex – pyruvate dehydrogenase complex, A complex multienzyme system that catalyses the conversion of (pyruvate + CoA + NAD) to (acetyl CoA + CO2 + NAD).

peptide - Small compound formed by the bonding of two or more amino acids. Larger chains of linked amino acids are called polypeptides or proteins. 

pH -- A measure of acidity/alkalinity. pH = -log10[H+].

phagocyte -- Leukocyte capable of ingesting and digesting micro-organisms.

phenotype -- The appearance or physiological characteristic of an individual that results from the interaction of the genotype and the environment.

phosphagen -- The term given to both high energy phosphate compounds, adenosine triphosphate and phosphocreatine.

phosphodiesterase -- An enzyme that cleaves phosphodiesters to give a phosphomonoester and a free hydroxyl group

phospholipids -- Fats containing a phosphate group that on hydrolysis yield fatty acids, glycerol, and a nitrogenous compound. Lecithin is an example. Phospholipids are important components of membranes.

Pi -- Inorganic phosphate (HPO42-).

plasma -- The liquid portion of the blood in which the blood cells are suspended. Typically accounts for 55-60% of the total blood volume. Differs from serum in that it contains fibrinogen, the clot-forming protein.

polypeptides              a peptide which upon hydrolysis yields more than two amino acids

polyphenols -- A large class of naturally occurring compounds that include the flavonoids,flavonols, flavonones and anthocyanidins. These compounds contain a number of phenolic hydroxyl (-OH) groups attached to ring structures which confers them with powerful antioxidant activity.

polysaccharide -- Polymers of (arbitrarily) more than about ten monosaccharide residues linked glycosidically in branched or unbranched chains. Examples include starch and glycogen.

pose no adverse health risks.

postabsorptive state                 -- The period after a meal has been absorbed from the gastro-intestinal tract. BMR measurements are usually performed 12 hours after the last meal.

power       -- Work performed per unit of time.

precursor -- a substance from which another, usually more active or mature substance is formed

prohormones -- A protein hormone before processing to remove parts of its sequence and thus make it active.

protease -- An enzyme that catalyses the digestion or cleavage of proteins.

protein -- Biological macromolecules composed of a chain of covalently linked amino acids. Proteins may have structural or functional roles.

protein breakdown -- See protein degradation

protein degradation – The process in which the individual amino acids from a protein are disconnected.

protein synthesis -- The process in which individual amino acids, whether of exogenous or endogenous origin, are connected to each other in peptide linkage in a specific order dictated by the sequence of nucleotides in DNA.

PUFA        (poly-unsaturated fatty acid) – Fatty acid (FA) that contains two or more double bonds. 

pyruvate – 3-carbon molecule that is the end product of glycolysis.

pyruvate dehydrogenase (PDH) -- The enzyme catalysing the conversion of pyruvate to acetyl CoA.

Ra (rate of appearance) -- Usually referring to the rate at which a substance enters the blood circulation.

radiation -- Transfer of energy waves that are emitted by one object and absorbed by another (e.g. solar energy from sunlight).

rate-limiting enzyme -- An enzyme in a metabolic pathway that regulates the slowest step in the pathway, and hence limits the rate of flux through the pathway.

rating of perceived exertion (RPE) -- A subjective rating, on a numerical scale, used to express the perceived difficulty of a given exercise task.

RBC -- Red blood cell (erythrocyte).

Rd (rate of disappearance) -- Usually referring to the rate at which a substance leaves the blood circulation.

RDA (recommended daily allowance) -- Recommended intake of a particular nutrient that meets the needs of nearly all (97%) healthy individuals of similar age and gender. The RDAs are established by the Food and Nutrition Boards of the National Academy of Sciences.

RDI (reference daily intake) -- Nutrient intake standards set by the FDA based on the 1968 RDA for various vitamins and minerals. RDIs have been set for infants, toddlers, people over 4 years of age and pregnant and lactating women.

reactive hypoglycemia – see rebound hypoglycemia

rebound hypoglycemia – reactive hypoglycemia. A decrease in blood glucose concentration to hypoglycemic levels (<3.5 mmol/l) in response to carbohydrate feeding prior to exercise. The carbohydrate will increase insulin concentration resulting in an increased uptake of glucose by tissues. When exercise is initiated glucose uptake by the muscle will further increase without an increase in hepatic glucose output resulting in a decrease in blood glucose concentration.

reduction -- A reaction in which a molecule gains electrons.

relative humidity -- The percentage of moisture in the air compared to the amount of moisture needed to cause saturation, which is taken as 100% 

RER (respiratory exchange ratio) -- The ratio of carbon dioxide produced divided by oxygen consumption, representing a measure of substrate utilization at the whole body level.

ribosome -- Very small organelle composed of protein and RNA that is either free in the cytoplasm or attached to the membranes of the endoplasmic reticulum of a cell. The site of protein synthesis.

RMR (resting metabolic rate) -- Energy expenditure under resting conditions.

RNA (ribonucleic acid) – A nucleic acid esential for protein synthsesis (mRNA: messenger RNA; tRNA: transfer RNA; rRNA: ribosomal RNA).

RNI (recommended nutrient intake) -- Defined as the level of intake required to meet the known nutritional needs of more than 97.5% of healthy persons. In the UK the RNI is very similar to the original RDA.

ROS (reactive oxygen species) -- Collective name for free radicals and other highly reactive molecules derived from molecular oxygen. ROS include superoxide radical (O2-.),  hydroxyl radical (OH-.), hydrogen peroxide (H2O2) and perchlorous acid (HOCl).

RQ (respiratory quotient) --      The ratio of the rate of carbon dioxide production divided by the rate of oxygen consumption, which can be used to establish the approximate pattern of substrate utilization by an organ or tissue (e.g. muscle).

saccharine -- An artificial sweetener made from coal tar. 

sarcolemma -- The cell membrane of a muscle fiber.

sarcomere -- The smallest contractile unit or segment of a muscle fiber and is defined as the region between two Z lines.

sarcoplasm -- The cytoplasm or intracellular fluid within a muscle fiber

SD (standard deviation) -- A measure of variability about the mean. Sixty-eight percent of the population is within one standard deviation above and below the mean, while about 95 percent of the population is within two standard deviations of the mean.

SE (standard error) -- A measure of variability about the mean. 

serotonin -- A brain neurotransmitter; also known as 5-Hydroxy tryptamine (5-HT) .

serum       -- Fluid left after blood has clotted.

SGLT –  sodium dependent glucose transporter 

short chain fatty acid (SCFA) -- A fatty acid containing 6 or less carbon atoms.

smooth muscle -- A specializes type of non-striated muscle tissue composed of single nucleated fibers. It contracts in an involuntary rhythmic fashion in the walls of visceral organs

sodium glucose transporter  (SGLT) – Carrier protein that cotransports sodium and glucose across a cell membrane.

sodium pump – common name for the sodium-potassium-ATPase that helps to establish the resting membrane potential of a cell.

soluble fiber --Fiber that dissolves well in water 

solute -- A substance dissolved in a solvent liquid such as water.

stable isotope            -- An isotope is a specific form of a chemical element. It differs from atoms of other forms (isotopes) of the same element in the number of neutrons in its nucleus. “Stable” refers to the fact that the isotope is not radioactive, in contrast to some other types of isotopes.

starch       -- A carbohydrate made of multiple units of glucose attached together by bonds that can be broken down by human digestion processes. Starch is also known as complex carbohydrates.

steroid -- A complex molecule derived from the lipid cholesterol. Contain four interlocking carbon rings.

substrate -- The reactant molecule in a reaction catalysed by an enzyme.

sucrose -- A disaccharide consisting of a combination of glucose and fructose, table-sugar.

supercompensation of muscle glycogen – Higher than normal muscle glycogen concentrations that can be achieved with a combination of exercise and diet.

TCA cycle (tricarboxylic acid cycle) -- A series of reactions that takes place in the mitochondrion. Also known as the Krebs cycle, after Hans Krebs who first described the reactions involved, or the citric acid cycle, as citrate is one of the key intermediates in the process. The reactions involve combination of acetyl-CoA with oxaloacetate to form citrate, a 6-carbon tricarboxylic acid. A series of reactions leads to the sequential loss of hydrogen atoms and CO2, resulting in the regeneration of oxaloacetate.

testosterone -- The male sex hormone responsible for male secondary sex characteristics at puberty; it has anabolic and androgenic effects. Responsible for aggressive behavior.

thermic effect of exercise (TEE) -- The energy required for exercise, increased muscle contraction increases heat production.

thermic effect of food (TEF) – See diet-induced thermogeneisis.

thermogenesis -- The production of heat; metabolic processes in the body generate heat constantly.

thermoreceptors -- Sensory cells capable of detecting changes in temperature.

tissue -- An organised association of similar cells that perform a common function (e.g. muscle tissue).

transamination -- Reaction involving the transfer of an amino (NH2) group from an amino acid to a ketoacid.

transcription              -- The process by which RNA polymerase produces single-stranded RNA complimentary to one strand of the DNA.

transit time -- The time that food stays in the gastrointestinal tract.

translation -- The process by which ribosomes and tRNA decipher the genetic code in mRNA in order to synthesise a specific polypeptide or protein.

triacylglycerol -- Also known as triacylglycerol, the storage form of fat. Composed of three fatty acid molecules linked to a 3-carbon glycerol molecule.

triad (of female athlete) -- The three conditions that are prevalent in female athletes: amenorrhoea, disordered eating and osteoporosis are collectively known as a syndrome called the “female athlete triad”. 

triglyceride – Also known as triacylglycerol, the storage form of fat. Composed of three fatty acid molecules linked to a 3-carbon glycerol molecule

tRNA         (transfer ribonucleic acid) – Transports amino acids to ribosomes where protein synthesis takes place.

TRP (tryptophan) -- An essential amino acid.

Type I diabetes mellitus (insulin dependent diabetes mellitus) -- A chronic condition in which the pancreas makes little or no insulin because the beta cells have been destroyed. The body is then not able to use the glucose (blood sugar) for energy.

type I fibers -- small diameter muscle cells that contain relatively slow acting myosin ATPases and hence contract slowly. Their red colour is due to the presence of myoglobin. These fibers possess a high capacity for oxidative metabolism, are extremely fatigue resistant and specialized for the performance of repeated contractions over prolonged periods.

type II fibers -- Muscle cells that are much paler than Type I fibers, because they contain little myoglobin. They possess rapidly acting myosin ATPases and so their contraction (and relaxation) time is relatively fast. A high activity of glycogenolytic and glycolytic enzymes endows Type II fibers with a high capacity for rapid (but relatively short-lived) ATP production in the absence of oxygen (anaerobic capacity). Hence, these fibers are best suited for delivering rapid, powerful contractions for brief periods

UFA (unsaturated fatty acid) – Fatty acid (FA) containing at least one double bond within its hydrocarbon chain.

UL -- Tolerable upper intake level; the highest level of daily nutrient intake likely to 

urea -- End product of protein metabolism. Chemical formula: CO(NH2)2.

uric acid -- a crystalline body, present in small quantity in the urine of man and most mammals.

urine -- Fluid produced in the kidney and excreted from the body. Contains urea, ammonia and other metabolic wastes.

URTI -- Upper respiratory tract infections like colds and flu.

VCO2         -- Rate of carbon dioxide production.

vegan -- Vegetarian who eats no animal products. 

vegetarian -- One whose food is of vegetable or plant origin.

vitamin -- An organic substance necessary in small amounts for the normal metabolic functioning of the body. Must be present in the diet because the body cannot synthesise it (or cannot synthesise an adequate amount of it).

Vitamin B1 – Thiamine.

Vitamin B12 – Cyanocobalamin. 

Vitamin B2 – Riboflavin.

Vitamin B6 – Pyridoxine.

Vitamin C – Ascorbic acid.

Vitamin D – Cholecalciferol; the product of irradiation of 7-dehydrocholesterol found in the skin.

Vitamin E – Alpha tocopherol.

Vitamin K -- Menoquinone. 

VLDL         (very low density lipoproteins) -- A protein-lipid complex in the blood plasma that 

VO2 -- Rate of oxygen uptake.

VO2max -- Maximal oxygen uptake; the highest rate of oxygen consumption by the body which can be determined in an incremental exercise test to exhaustion.

W (watt) – Unit of power or work rate (J/s)

water -- The universal solvent of life (H2O). The body is composed of 60% water. 

WBC -- White blood cell (leukocyte)

wet-bulb globe thermometer index (WBGT Index ) -- A heat-stress index based upon four factors measured by the wet-bulb globe thermometer.

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