NASM-GFS key terms

An imaginary plane that divides the body into left and right halves; movements such as flexion, extension, dorsiflexion, and plantarflexion occur parallel to it.

An imaginary plane dividing the body into front and back halves; abduction, adduction, and lateral flexion occur parallel to it.

An imaginary plane dividing the body into upper and lower halves; rotation and horizontal abduction occur parallel to it.

The vocabulary used to describe movement at a joint, including flexion, extension, abduction, adduction, rotation, circumduction, and inversion or eversion, each tied to a plane of motion.

The muscle primarily responsible for producing a given joint motion; also called the prime mover.

The muscle that opposes the agonist and lengthens or controls the rate of movement during a given action.

A muscle that assists the agonist in producing movement, often by neutralizing unwanted motion or stabilizing a joint.

A muscle that contracts to hold a joint or body segment in place so another muscle can produce movement effectively.

The cooperative action of two or more muscles pulling on a segment from different directions to produce a combined movement or rotation around a joint.

The principle that a muscle produces the most force at its resting length and less force when overly shortened or overly lengthened.

A muscle action in which the muscle shortens while producing force, as when lifting a weight against gravity.

A muscle action in which the muscle lengthens while producing force, typically controlling or decelerating a load.

A muscle action in which tension is produced without a change in muscle length or joint angle.

The nervous system process in which contraction of a muscle is accompanied by reduced activation of its antagonist, allowing smoother joint motion.

A reduction in muscle activation that follows high tension in the same muscle, mediated by the Golgi tendon organ.

A sensory receptor within muscle that detects changes in muscle length and the speed of that change, triggering a stretch reflex.

A sensory receptor located where muscle meets tendon that detects tension and helps regulate force output.

An automatic contraction of a muscle in response to a rapid stretch, mediated by the muscle spindle.

Slow-twitch fibers that are fatigue resistant and suited to sustained, low-intensity activity such as posture and endurance work.

Fast-twitch fibers that produce high force quickly but fatigue faster, supporting strength, power, and sprint activities.

How quickly a muscle or group of muscles can generate force; a key quality in power and explosive training.

The product of force and velocity, describing how much work is done per unit of time.

The training principle that adaptations reflect the specific demands imposed, so programs must match the desired outcome.

The principle of gradually increasing training stress over time so the body continues to adapt.

Specific adaptation to imposed demands: the body adapts specifically to the type of stress placed on it.

The planned manipulation of training variables over time, dividing training into phases to manage fatigue and peak performance.

The longest planning cycle in a periodized program, typically spanning a full training year or competitive season.

A training phase within a macrocycle, usually lasting several weeks to a few months, with a specific emphasis.

The shortest planning unit in periodization, typically a week or a few weeks of training.

A systematic, phased approach to program design that progresses clients through stabilization, strength, and power levels of training.

Training that develops the strength and coordination of the trunk and pelvic muscles to maintain spinal and pelvic alignment during movement.

A technique of gently pulling the navel toward the spine to activate deep abdominal muscles and improve trunk stability.

Co-contraction of the trunk and abdominal muscles to stiffen the spine and maintain a neutral position under load.

A systematic observation of a client standing still, viewed from front, side, and back, to identify alignment deviations.

Observation of a client performing a movement such as a squat or single-leg stance to reveal imbalances that appear under motion.

A transitional movement screen in which a client squats with arms overhead, used to observe mobility and stability throughout the kinetic chain.

A pre-participation screening questionnaire that identifies whether a client needs medical clearance before beginning or progressing exercise.

The process of gathering health history and risk information to classify a client's readiness and safe starting intensity for exercise.

A client's documented voluntary agreement to participate after being told the purpose, risks, and benefits of an activity.

Muscle discomfort that appears roughly a day or more after unfamiliar or intense exercise and typically resolves within days.

A state of persistent fatigue and reduced performance caused by training stress that exceeds recovery.

Exercise using a rapid stretch followed by a forceful contraction, often with jumping, to build power and rate of force production.

Controlled movement through a joint's range of motion, used in warm-ups to prepare muscles and increase blood flow.

Holding a muscle in an elongated position for a period to improve flexibility, typically performed after activity or in separate flexibility sessions.