A single muscle cell, usually classified according to strength, speed of contraction, and energy source.
Protein structures that make up muscle fibers.
An increase in the size of muscle fibers, usually stimulated by muscular overload, as occurs during strength training.
A decrease in the size of muscle fibers.
An increase in the number of muscle fibers.
Red muscle fibers that are fatigue resistant but have a slow contraction speed and a lower capacity for tension; usually recruited for endurance activities.
White muscle fibers that contract rapidly and forcefully but fatigue quickly; usually recruited for actions requiring strength and power.
The ability to exert force rapidly.
A motor nerve (one that initiates movement) connected to one or more muscle fibers.
The improvement in the body's ability to recruit motor units, brought about through strength training.
A tough band of fibrous tissue that connects a muscle to a bone or other body part and transmits the force exerted by the muscle.
A tough band of tissue that connects the end of the bones to other bones or supports organs in place.
The principal male hormone, responsible for the development of secondary sex characteristics and important in increasing muscle size.
Repetition Maximum (RM)
The maximum amount of resistance that can be moved a specified number of times.
The number of times an exercise is performed during one set.
Static (isometric) exercise
Exercise involving a muscle contraction without a change in the length of the muscle.
Dynamic (isometric) exercise
Exercise involving a muscle contraction with a change in the length of the muscle.
Concentric muscle contraction
A dynamic contraction in which the muscle gets shorter as it contracts.
Eccentric muscle contraction
A dynamic contraction in which the muscle lengthens as it contracts; also called a pliometric contraction
Constant resistance exercise
A type of dynamic exercise that uses a constant throughout a joint's entire range of motion.
Variable resistance exercise
A type of dynamic exercise that uses a changing load, providing a maximum load throughout the joint's entire range of motion.
Eccentric (pliometric) loading
Loading the muscle while it is lengthening; sometimes called negatives.
Rapid stretching of a muscle group that is undergoing eccentric stress (the muscle is exerting force while it lengthens), followed by a rapid concentric contraction.
Moving a load as rapidly as possible.
The application of force at a constant speed against an equal force.
A person who assists with a weight training exercise done with free weights.
A group of repetition followed by a rest period.
A muscle in a state of contraction, opposed by the action of another muscle, it's antagonist.
A muscle that opposes the action of another muscle, it's agonist.
Range of motion
The full motion possible in a joint.
Semielastic structures, composed primarily of connective tissue, that surround major joints.
Tissue of the human body that include skin, fat, linings of internal organs and blood vessels, connective tissues, tendons, ligaments, muscles and nerves.
White fibers that provide structure and support in connective tissue.
Yellow fibers that make connective tissue flexible.
A nerve that sends information about the muscular and skeletal systems to the nervous system.
A technique in which a muscle is slowly and gently stretched and then held in the stretched position.
A technique in which muscles are stretched by the force generated as a body part is repeatedly bounced, swung, or jerked.
A technique in which muscles are stretched by moving joints slowly and fluidly through their range of motion in a controlled manner; also called functional stretching.
A technique in which muscles are stretched by force applied by an outside source.
A technique in which muscles are stretched by the contraction of the opposing muscles.
Bony segments composing the spinal column that provide structural support for the body and protect the spinal cord.
An elastic disk located between adjoining vertebrae, consisting of a gel-and water-filled nucleus surrounded by fibrous rings; serves as a shock absorber for the spinal column.
The base of each of the 31 pairs of spinal nerves that branch off the spinal cord through spaces between vertebrae.
The fat in the body necessary for normal body functioning.
Nonessential (storage) fat
Extra fat or fat reserves stored in the body.
Connective tissue in which fat is stored.
Percent body fat
The percentage of total body weight that is composed of fat.
Characterized by a body weight above a recommended range for good health; ranges are set through large-scale population surveys.
Severely overweight, characterized by an excessive accumulation of body fat; overfat. Obesity may also be defined in terms of some measure of total body weight.
Absent or infrequent menstruation, sometimes related to low levels of body fat and excessive quantity or intensity of exercise.
Body mass index (BMI)
A measure of relatively body weight correlating highly with more direct measures of body fat, calculated by dividing total body weight (in kilograms) by the square of body height (in meters).
Female Athlete Triad
A condition consisting of three interrelated disorders; abnormal eating patterns (and excessive exercising) followed by lack of menstrual periods (amenorrhea) and decreased bone density (premature osteoporosis).
A pressure-sensitive measuring instrument with two jaws that can be adjusted to determine thickness.