ISSA CPT key terms

The smallest working unit of a muscle fiber, running from one Z-line to the next. It holds overlapping actin and myosin filaments that shorten the fiber when the muscle contracts.

The accepted explanation of muscle shortening: myosin heads attach to actin and pull the filaments toward the sarcomere center, so the filaments slide past one another rather than changing length themselves.

One motor neuron plus every muscle fiber it activates. Fibers within a unit fire together, and recruiting units with more or larger fibers increases the force produced.

A stretch detector lying within skeletal muscle that senses how far and how quickly a muscle lengthens. It triggers a reflex contraction that resists the stretch and helps protect the joint.

A sensor at the muscle-tendon junction that monitors tension rather than length. When tension climbs very high it can dampen muscle output, which lowers the chance of strain injury.

The volume of blood the heart ejects each minute, equal to stroke volume multiplied by heart rate. It climbs during exercise to supply working muscle with more oxygen.

The quickest energy pathway, rebuilding ATP from stored creatine phosphate for roughly the first ten seconds of hard effort. It needs no oxygen and produces no lactate.

The breakdown of blood glucose or stored muscle glycogen into pyruvate, yielding ATP quickly. Without oxygen, pyruvate converts to lactate and the effort can only be held briefly.

Energy production that uses oxygen to break down carbohydrate and fat inside the mitochondria. It takes longer to reach full output but can supply ATP for hours of steady work.

The intensity at which blood lactate begins accumulating faster than the body clears it. Clients can only hold work above this point briefly, so it helps set tempo and interval paces.

The highest rate at which a person can take in and use oxygen during intense exercise, usually reported in milliliters per kilogram per minute. It is a standard marker of aerobic capacity.

Excess post-exercise oxygen consumption: oxygen use that stays above resting levels after training while the body restores ATP, clears byproducts, and cools down. It adds a modest amount to total calorie expenditure.

The difference between a client's resting and maximum heart rate. Target intensities are often prescribed as a percentage of this range so the workload matches the individual's fitness.

An increase in muscle fiber size, largely from added contractile protein after repeated resistance training with sufficient protein and calories. It is distinct from early strength gains driven by neural learning.

The turning effect a force has around a joint axis, found by multiplying force by the perpendicular distance to that axis. Muscles generate torque to move a limb or resist an external load.

The perpendicular distance from a joint's axis of rotation to the line of action of a force. A longer moment arm means the same force creates more rotational effect at the joint.

A muscle's force output depends on its current length. Fibers produce the most tension near resting length, where actin and myosin overlap best, and less when overstretched or overly shortened.

Concentric force falls as movement speed rises, while eccentric actions can exceed isometric force. This explains why fast repetitions must use lighter loads than slow ones.

An exercise in which the far end of the limb is fixed against a surface, such as a squat or push-up. These movements usually involve several joints and are common in functional programming.

A brief pre-exercise screening questionnaire that flags symptoms, medical conditions, or medications which may make activity unsafe without a physician's clearance first.

A documented agreement in which the client confirms they understand the purpose, risks, benefits, and alternatives of training or testing before participation begins.

A quick screening ratio of weight to height squared. It cannot separate fat from lean tissue, so fit, muscular clients are often misclassified and it should never stand alone.

A whole-body screen performed with arms raised and a bodyweight squat. The trainer watches for compensations such as inward knee collapse or forward trunk lean to identify mobility and stability limits.

The client's own effort score on a numerical scale, commonly 6 to 20 or 0 to 10. It is valuable when heart rate readings are unreliable or medications alter heart rate response.

A condition that makes a specific exercise or test inadvisable. Absolute contraindications mean do not proceed; relative ones mean proceed only with caution, modification, or medical clearance.

Deliberately raising training demand over time through load, volume, or movement difficulty as the body adapts, so fitness improves without outpacing the client's ability to recover.

Specific Adaptation to Imposed Demands: the body adapts to exactly the stress applied. Programs must therefore mirror the target outcome in muscles used, joint angles, speed, and energy system.

The heaviest load a client can lift once with sound technique. It anchors percentage-based prescriptions, although estimating it from a multi-rep set is often safer for beginners.

Total work completed, usually calculated as sets multiplied by repetitions multiplied by load. Coaches track it to judge whether training stress is rising at an appropriate rate.

Planned manipulation of training variables over weeks and months, moving through phases with different goals such as base building, strength, or peaking, to sustain progress and reduce overtraining risk.

A scheduled stretch of reduced volume or intensity, typically about a week, that allows accumulated fatigue to clear so the client returns fresher and performs better.

The relationship between calories consumed and calories expended. A surplus supports weight gain, a deficit drives loss, and near-equal intake maintains body weight over time.

The daily protein needed for tissue repair and growth. Clients doing resistance training generally need more than sedentary adults, spread across meals and supported by adequate total calories.

Blood glucose that has fallen too low, causing shakiness, sweating, confusion, or fainting. Clients using insulin or certain diabetes medications should carry fast carbohydrate and monitor around sessions.

Reduced bone density that increases fracture risk. Training should use controlled loading, postural work, and balance practice while avoiding loaded deep spinal flexion and high fall-risk activities.

The legal and professional boundaries of what a trainer may do, such as designing exercise programs but not diagnosing injuries or prescribing diets. It is set by law, certification, and employer policy.

A failure to provide the care a reasonable professional would provide, which results in client harm. Establishing it requires a duty of care, a breach, causation, and actual damages.

The duty to keep client health and personal information private, sharing it only with authorized parties who need it, consistent with ethical standards and applicable privacy regulations.