Glossary

macronutrient—Substance required in large amounts to sustain life (Carbohydrate, protein, fat, and water).

Mad Cow Disease—See BSE (Bovine spongiform encephalopathy).

maximal graded exercise test—See graded exercise test (GXT).

maximal heart rate (HRmax or MHR)—Maximal number of times an individual’s heart beats within one minute; HRmax is determined in part by age and genetics; also referred to as maximum heart rate.

maximal oxygen consumption (VO2max)—The highest volume of oxygen a person can consume during exercise; maximum-aerobic capacity; VO2max is a measure of maximal cardiovascular performance.

maximal oxygen uptake—See maximal oxygen consumption (VO2 max).

max—Maximum effort for one repetition of a weight training exercise; also expressed as one's "1-RM" or "one rep max."

medial—Anatomical term meaning situated or occurring in the middle of the body; toward the midline.

mega-dose (Mega-dosing)—A dose of a nutrient that is 10 times or more than the RDA for that nutrient.

megadose—Dose of a substance that is extremely high compared to the needs of the body.

menopause—Cessation of menstruation in the human female, usually occurring between the ages of 48 and 50.

mesomorph—A person whose body shape consists mostly of muscle, bone and connective tissue, with a predisposition to muscular development; compare ectomorph and endomorph.

meta-analysis—A quantitative technique in which the results of several individual studies are pooled to yield overall conclusions.

metabolic equivalents (METS)—A simplified system for classifying physical activities where one MET is equal to the resting oxygen consumption, which is approximately 3.5 milliliters of oxygen per kilogram of body weight per minute (3.5 ml/kg/min).

metabolic pathways—A series of consecutive enzymatic reactions that produce specific products; pathways involved in metabolic processes; Example, the breakdown of glucose, the storing of glycogen, the breakdown of fats, etc.

metabolic rate—The rate at which the body utilizes energy; Exercise raises the metabolic rate.

metabolism—The sum total of all chemical reactions taking place in a living organism; typically broken down into the energy producing and absorbing processes that are occurring in the body; Metabolism describes the energy utilized by the body.

meter—The division of music into measures or bars; Most music for exercise purposes may be counted in increments of 4, 8, 16 or 32.

MET—See metabolic equivalents (METs).

micronutrient—Substance required in small amounts to sustain life (Vitamins and minerals).

minerals—Inorganic substances needed in the diet in small amounts to help regulate bodily functions.

miniscal tear—A tear in the meniscal cartilage (found in the knee); Torn meniscus, a common and painful injury, plagues many athletes and dancers.

mirroring—Imitating another's behavior or attitudes.

mitochondria—Specialized subcellular structures located within body cells that contain oxidative enzymes needed by the cells to metabolize foodstuffs into energy sources; They are the source of energy in the cell and are involved in protein synthesis and lipid metabolism.

mitochrondria—Organelle responsible for aerobically generating energy.

modeling—The process of learning by observing and imitating others' behavior.

monounsaturated fats—A type of unsaturated fat (liquid at room temperature) that has one spot available on the fatty acid for the addition of a hydrogen atom; moderate intake is associated with a lower risk for cardiovascular disease; Example, oleic acid in olive oil; generally considered to be a "healthy" fat.

morbid obesity—This is a state of adiposity or overweight, in which body weight is 100 percent above the ideal and a body mass index of 45 or greater.

morbidity—The disease rate; the ratio of sick to well persons in a community.

mortality—The death rate, or ratio of deaths that take place to expected deaths.

motive force—The force that starts or causes a movement.

motor learning effect—Improvement in performance during the initial weeks of strength training due to more efficient motor unit utilization.

motor unit—A motor nerve and all the muscle fibers it stimulates; In the quadriceps muscle, one neuron can activate as many as 1,000 fibers. In the eye, where great precision is required, one nerve cell may control only 3 fibers.

MSG (monosodium glutamate)—MSG is the sodium salt of glutamic acid. Glutamic acid, or glutamate, is one of the most common amino acids found in nature. (see glutamate). In the early part of the century, MSG was extracted from seaweed and other plant sources. Today, MSG is produced in many countries around the world through a fermentation process of molasses from sugar cane or sugar beets, as well as starch and corn sugar.

muscle cramp—Painful involuntary contraction due to overexertion and imbalance of oxygen, minerals and carbon dioxide; Stretch the cramped muscle with one hand and squeeze and release the body of the muscle rhythmically with the other hand. Deep breathing helps to release cramps since it increases oxygen availability.

muscle fiber—A muscle cell.

muscle spindle—The sensory organ within a muscle that is sensitive to stretch and thus protects the muscle from being stretched too far; Muscle spindles cause the muscle to contract instead of allowing it to stretch during rapid stretching.

muscle tear—The tearing of a muscle bundle caused by severe stretching accompanied by acute pain and spasm; A muscle tear is called a strain.

muscle tone—The degree of tension and vigor in a gross muscle; Muscle tone is increased through weight training, which results in a greater number of muscle fibers "firing" while at rest.

muscle-head—Slang term used to describe a person who works out in the gym all the time and has become quite muscular; often used in a derogatory manner.

muscle-pump—Slang term used to describe a feeling of increased size and power in one’s muscles.

muscular endurance—The ability to sustain a sub-maximal contraction (isometric) over time, or the ability to perform a maximum number of sub-maximal repetitions (isotonic).

muscular strength—The ability of the muscle to exert force; usually measured with one maximal repetition or with a hand dynamometer.

myocardial infarction (MI) —An interruption of blood supply to the heart; may be caused by blockage of a heart artery caused by atherosclerosis or a blood clot; MI causes tissue damage to the heart muscle. It may begin with a crushing chest pain that moves to the left arm, neck or upper abdomen, and it may seem like indigestion. Signs of MI are rapid, irregular heart rate, low blood pressure and fever. Emergency treatment may require CPR; commonly called a heart attack.

myofibril—The functional units within muscle fibers that cause contractions; The more myofibrilla (plural) a person has, the greater his or her strength.

myoglobin—Protein that holds and stores oxygen within the muscles and tissues.

myosin—Thick contractile protein in a myofibril which overlaps with actin to produce contractions.

myotatic stretch reflex—Muscular reflex created by excessive muscle spindle stimulation; prevents potential tissue damage during periods of rapid muscle stretching.