NASM GFI key terms

The imaginary plane that divides the body into left and right halves and permits flexion and extension movements, such as a biceps curl or a squat, to occur around a medial-lateral axis.

The plane dividing the body into front and back halves, where abduction, adduction and lateral flexion take place, as in a side lunge or lateral shoulder raise.

The plane dividing the body into upper and lower halves, allowing rotation, horizontal adduction and horizontal abduction, such as during a cable rotation or a chest fly.

A muscle action in which tension is produced while the muscle lengthens under load, controlling and decelerating movement; it is often where soreness and strength gains are most pronounced.

A muscle action in which tension is produced while the muscle shortens, overcoming external resistance and accelerating a joint segment, such as the upward phase of a squat.

A muscle action in which tension develops without a change in muscle length or joint angle, as when holding a plank or pausing at the bottom of a push-up.

The principle that a muscle produces the greatest force at its resting length and less force when overly shortened or lengthened, which shapes exercise setup and range-of-motion choices.

The inverse relationship showing that a muscle can produce more force at slower shortening speeds and less force as contraction velocity increases, guiding tempo and loading decisions.

The ability of the nervous system to recruit, synchronize and coordinate motor units properly, producing appropriate force and joint control during movement.

The muscle primarily responsible for producing a desired joint motion, such as the gluteus maximus during hip extension in a deadlift.

The muscle that opposes the agonist at a joint and must lengthen or relax to allow the intended movement, such as the biceps brachii during a triceps extension.

A muscle that assists the agonist in producing movement, often by contributing force or by neutralizing unwanted joint motion so the prime mover works efficiently.

A muscle that contracts to hold a joint or body segment steady while another segment moves, supporting alignment and efficient force transfer during an exercise.

The neurological process in which contraction of a muscle is accompanied by relaxation of its antagonist, allowing smoother joint motion; tightness can disrupt this normal interplay.

A reflex response in which a sustained contraction of a muscle, or stimulation of its tendon, reduces that muscle's own activation, which underlies static stretching and self-myofascial release effects.

A single motor neuron together with all the muscle fibers it innervates; motor units are recruited in order of size to match force output to demand.

The ability of muscles to generate force quickly, a key quality for power training and for reacting to unexpected balance challenges or daily demands.

The coordinated muscular and sensory regulation of body alignment to maintain balance and stability, both statically and while moving, during exercise and daily activity.

The alignment and positioning of the body at rest, often observed from anterior, lateral and posterior views to identify muscle imbalances and joint deviations.

Body alignment maintained while moving, such as during an overhead squat or single-leg squat, revealing compensation patterns that static observation may not show.

Five key body regions - foot and ankle, knee, lumbo-pelvic-hip complex, shoulder, and head and neck - observed together to spot movement compensations during an assessment.

A transitional movement screen in which the client squats with arms overhead, allowing observation of bilateral symmetry, mobility and stability across the kinetic chain checkpoints.

A posture in which the front of the pelvis drops and the lower back arches excessively, often linked with tight hip flexors and erector spinae and lengthened abdominals and glutes.

A predictable pattern of tight hip flexors and lumbar extensors paired with weak abdominals and gluteals, commonly associated with anterior pelvic tilt and low-back stress.

A pattern of tight upper trapezius, levator scapulae and pectorals combined with weak deep cervical flexors and lower trapezius, often producing rounded shoulders and forward head.

A resting alignment in which the head sits ahead of the shoulders, increasing cervical loading and often accompanying rounded shoulders and thoracic kyphosis.

Movement of the top of the foot toward the shin, a mobility requirement for squatting, lunging and landing mechanics; restriction often shows as foot flattening or heel lift.

A self-applied technique using a foam roller or similar tool to apply sustained pressure to soft tissue, intended to reduce tension and improve range of motion before static stretching.

Slowly moving a joint to the end of its available range and holding the position, typically for 30 seconds, to improve flexibility and extensibility of muscle and connective tissue.

The range of motion a person can achieve and control without external assistance, developed through techniques that combine stretching with neuromuscular control and stabilization.

Controlled, movement-based stretching that takes a joint through its full range of motion, used in warm-ups to raise tissue temperature and prepare the body for activity.

A systematic, periodized programming framework organized into five phases that progresses clients through stabilization, strength and power emphases based on goals and readiness.

The fundamental program design components - repetition, sets, intensity, tempo, rest interval, exercise selection, exercise order and frequency - that determine the training stimulus.

The total amount of work performed in a session or cycle, commonly expressed as sets multiplied by repetitions, and manipulated to control fatigue and adaptation.

The planned, systematic variation of training variables over time into phases or cycles, aiming to manage fatigue, avoid plateaus and peak performance at appropriate moments.

The product of force and velocity, describing how quickly work is done; training for power requires moving moderate loads with maximal intent and adequate rest.

The trained assistant's role in helping a client safely complete or abort a repetition, requiring proper positioning, communication and knowledge of which exercises demand a spotter.

Modifying an exercise to reduce difficulty or demand, such as decreasing load, range of motion or stability requirements, so a client can perform it with sound technique.

Systematically increasing exercise challenge through added load, volume, complexity or reduced stability once a client demonstrates competent, pain-free technique.

The deepest abdominal muscle, wrapping the waist to compress the abdomen and contribute to spinal and pelvic stability during movement and load-bearing tasks.

A forced exhalation against a closed airway that raises internal pressure and briefly stabilizes the spine, but also elevates blood pressure and is unsuitable for many clients.

A readiness model describing progression from precontemplation through contemplation, preparation, action and maintenance, helping the coach match strategies to where a client currently stands.

A person's belief in their own capability to perform a specific behavior or task successfully, which strongly predicts adherence and persistence in an exercise program.

A collaborative, client-centered conversation style using open questions, affirmations, reflections and summaries to strengthen a client's own reasons for behavior change.

A goal-setting format requiring objectives to be specific, measurable, attainable, relevant and time-bound, making progress observable and supporting client commitment.

The legally defined boundaries of what a certified fitness professional may and may not do, including avoiding diagnosis, prescription and treatment of medical conditions.

The process of clearly explaining assessment or training procedures, risks and benefits so a client can voluntarily agree to participate before activity begins.

A structured screening form collecting medical conditions, medications, injuries and symptoms to identify risk factors and determine whether medical clearance is needed before exercise.

Directing a client to an appropriate licensed healthcare professional when findings fall outside the fitness professional's training or legal scope, such as pain or unexplained symptoms.

The limits that keep the coach-client relationship focused, respectful and appropriate, protecting both parties and preserving trust and objectivity.

Ongoing learning required to renew certification, keeping knowledge current with research and practice while documenting professional growth and competence.