valsalva maneuver—To force the breath against a closed throat, i.e., holding the breath, tightening the muscles, and making a strong effort to lift a weight; The valsalva maneuver is especially dangerous to clients with high blood pressure or heart disease.

variability—The training technique of changing (varying) exercise sessions to prevent overuse, to prevent injuries, and to increase interest and adherence while minimizing staleness in a training program.

variable—Any characteristic that may vary in study subjects, such as gender, age, body weight, diet, behavior, attitude or other attribute. In an experiment, the treatment is called the independent variable; it is the factor being investigated. The variable that is influenced by the treatment is the dependent variable; it may change as a result of the effect of the independent variable.

variable resistance equipment—Strength training equipment which can, through the use of elliptical cams and other such technology, vary the amount of weight being lifted to match the strength curve for a particular exercise; Example, Nautilus machines.

vascularity—The degree to which veins are observable.

vasoconstriction—Decrease in diameter of a blood vessel.

vasodilation—Increase in the diameter of a blood vessel.

vasodilator—An agent (motor nerve or drug) that acts to relax (dilate) a blood vessel.

vegan—A "pure" vegetarian who excludes all animal-derived foods from the diet including dairy products, fish, eggs -- even honey.

vegetarian—According to the Vegetarian Resource Group, less than 1 percent of Americans are true vegetarians. Such people never eat meat, fish or poultry, although they may eat foods derived from animals such as dairy products and eggs (lacto-ovo vegetarians). There are even fewer vegans, strict vegetarians who avoid all animal-derived foods -- even honey.

veins—Blood vessels that carry blood, usually deoxygenated (except in the case of the pulmonary vein), to the heart.

ventricle—One of the two (left and right) lower chambers of the heart; The muscular left ventricle pumps blood to the body and is the portion of the heart in which adaptation to exercise is usually most visible. The smaller right ventricle pumps blood to the lungs.

vitamins—Vitamins are organic compounds that are nutritionally essential in small amounts to control metabolic processes and cannot be synthesized by the body. Vitamins are usually classified by their solubility, which to some degree determines their stability, occurrence in foodstuffs, distribution in body fluids, and tissue storage capacity. Each of the fat-soluble vitamins A, D, E and K has a distinct and separate physiologic role. Several have antioxidant properties which depress the effects of metabolic byproducts called free radicals, which are thought to cause degenerative changes related to aging. Most of the water-soluble vitamins are components of essential enzyme systems; many are involved in the reactions supporting energy metabolism. These vitamins are not normally stored in the body in appreciable amounts and are normally excreted in the urine. Thus, a daily supply is desirable to avoid depletion and interruption of normal physiologic functions.

VO2 max—See maximal oxygen consumption.