Fitness Terms Glossary: 35 Terms Explained

This glossary covers 35 terms you will encounter when working with a personal trainer, researching fitness programs, or reading exercise science content. Definitions are written for practical use -- clear enough to act on, not simplified to the point of losing accuracy. Where relevant, results-vary context is included.

Training Format and Program Terms

AMRAP - As Many Rounds (or Reps) As Possible. A timed workout format in which you complete a circuit or movement as many times as possible within a set window, typically 5 to 20 minutes. Measures work capacity over time and is common in CrossFit and HIIT programming.

EMOM - Every Minute On the Minute. A workout format in which you start a set exercise at the top of each minute and rest for whatever time remains before the next minute begins. Used to train pacing and work-to-rest discipline.

Superset - Two exercises performed back to back without rest between them. An antagonist superset pairs opposing muscle groups (biceps curl followed by triceps extension). A compound superset pairs two exercises for the same muscle group.

Progressive Overload - The principle that training stimulus must increase over time to continue driving adaptation. Applied by adding weight, volume (more sets or reps), frequency, or density (less rest) across training cycles. Without progressive overload, training produces maintenance, not improvement.

Periodization - The planned variation of training variables -- volume, intensity, exercise selection -- across a defined time horizon, typically weeks to months. Linear periodization increases load steadily each week. Undulating periodization varies load within a week. Block periodization concentrates specific training qualities across multi-week phases.

Deload - A planned reduction in training volume or intensity, typically lasting one week, inserted into a multi-week training program. The purpose is recovery and adaptation consolidation rather than continued loading. A deload reduces injury risk and accumulated fatigue.

Rep (Repetition) - One complete execution of an exercise through its full range of motion. One squat descent and ascent equals one rep. Training programs specify rep counts to control volume and intensity.

Set - A group of consecutive reps performed without stopping. Three sets of ten means ten reps, then rest, then ten more, then rest, then ten more. Volume is calculated as sets multiplied by reps.

1RM (One Rep Max) - The maximum weight a person can lift for exactly one rep with proper form. Used as a reference point for setting training loads, typically expressed as percentages (e.g., 75% of 1RM for a working set). Direct testing carries injury risk; estimated 1RM formulas exist for indirect calculation.

RPE (Rate of Perceived Exertion) - A self-reported scale for measuring workout intensity. The Borg scale runs from 6 to 20; a modified version runs 0 to 10. Coaches often prescribe training at specific RPE levels (e.g., RPE 7 = roughly seven out of ten effort) to account for daily variation in readiness.

Exercise Science Terms

Hypertrophy - An increase in muscle size resulting from resistance training. Hypertrophy occurs when training volume and mechanical tension stimulate muscle protein synthesis above breakdown rates. Typical hypertrophy programming uses moderate weight (60 to 80 percent of 1RM) and 6 to 20 reps per set.

Muscle Protein Synthesis (MPS) - The process by which cells build new protein to repair and grow muscle tissue. Resistance training and adequate dietary protein both stimulate MPS. Research from the Journal of the International Society of Sports Nutrition suggests distributing protein across three to four meals per day optimizes MPS stimulation compared to eating the same total in fewer, larger meals.

VO2 Max - The maximum rate of oxygen consumption during intense exercise, measured in milliliters of oxygen per kilogram of body weight per minute. It is a primary indicator of cardiovascular fitness. Higher VO2 max correlates with better endurance performance and, in population studies, with long-term health outcomes. Individual VO2 max is trainable through consistent aerobic exercise.

Aerobic - Exercise performed at an intensity where oxygen is the primary energy source and can be sustained for extended periods. Walking, jogging, cycling, and swimming at conversational effort are aerobic. Aerobic training improves cardiovascular efficiency and fat oxidation capacity.

Anaerobic - Exercise performed at an intensity that outpaces the aerobic energy system, relying on stored energy (phosphocreatine and glycolysis) and producing lactate. Sprinting, heavy strength training, and HIIT intervals involve anaerobic metabolism. Work intervals in this range are limited to seconds to a few minutes before fatigue forces a reduction in intensity.

Lactate Threshold - The exercise intensity at which lactate accumulates in the blood faster than it can be cleared. Training at or near this threshold improves the ability to sustain higher intensities for longer. Endurance athletes and coaches use lactate threshold testing to set training zones and measure fitness progression.

EPOC (Excess Post-Exercise Oxygen Consumption) - Elevated oxygen uptake after exercise ends, sometimes called the afterburn effect. High-intensity exercise generates more EPOC than moderate-intensity exercise. The magnitude of EPOC-driven calorie burn is real but modest in most contexts -- typically 6 to 15 percent of calories burned during the workout itself.

BMI (Body Mass Index) - A number calculated from height and weight (weight in kg divided by height in meters squared) used as a population-level screening tool for weight status. BMI does not distinguish muscle from fat, and is a poor individual fitness indicator. A muscular person may have a high BMI while carrying low body fat. Used in research and clinical settings as an approximation, not a precision metric.

Body Composition - The proportion of fat mass to lean mass (muscle, bone, water, organs) in the body. A more informative measure than weight alone. Methods for assessing body composition include DEXA scan (most accurate), hydrostatic weighing, skinfold calipers, and bioelectrical impedance devices (least accurate, widely used due to cost).

Trainer Qualification Terms

NCCA-Accredited Certification - A personal trainer certification that has been reviewed and approved by the National Commission for Certifying Agencies. NCCA accreditation means the certification body has demonstrated that its exam meets defined standards for content validity, pass-rate analysis, and recertification requirements. The major NCCA-accredited certifications are NASM-CPT, ACE-CPT, NSCA-CPT, and ACSM-CPT. See our full guide to personal trainer certifications.

CPT (Certified Personal Trainer) - The base-level personal training credential. Most NCCA-accredited organizations offer a CPT designation that requires passing a proctored exam and demonstrating current CPR/AED certification. It is the entry point for professional personal training.

CSCS (Certified Strength and Conditioning Specialist) - An advanced NSCA credential aimed at trainers and coaches working with athletes. Requires a bachelor's degree in a related field and passing a two-part exam. More specialized than a base CPT in programming for performance outcomes.

CEU (Continuing Education Unit) - Credits required to maintain a professional certification. NCCA-accredited certifications require CEUs every two to three years. CEUs come from approved workshops, courses, or specialty credentials. A trainer with current CEUs is up to date with their certifying body's standards.

Workout and Nutrition Terms

Compound Exercise - An exercise that involves multiple joints and muscle groups simultaneously. Squats, deadlifts, bench press, rows, and pull-ups are compound movements. Programming centers compound exercises because they develop strength efficiently and produce more hormonal response per set than isolation movements.

Isolation Exercise - An exercise that targets a single muscle group across a single joint. Biceps curls, triceps pushdowns, and leg extensions are isolation exercises. Used to address specific weaknesses or provide additional volume for a muscle group after compound work.

Macronutrient (Macro) - One of three primary nutrient categories: protein, carbohydrate, and fat. Each provides calories and performs distinct physiological functions. Protein provides 4 calories per gram; carbohydrates provide 4 calories per gram; fat provides 9 calories per gram. Coaches use macro ratios to set calorie distribution goals aligned with body composition or performance targets.

Calorie Deficit - The condition in which total calories consumed are less than total calories expended over a period of time. A calorie deficit is the necessary condition for fat loss. The rate of loss depends on the size of the deficit, body composition, and individual metabolic factors. No training program overrides a sustained calorie surplus.

Protein Synthesis - See Muscle Protein Synthesis (MPS) above. The term is also used broadly to describe the cellular process of building proteins for all body functions, not only muscle.

Creatine - A naturally occurring compound stored in muscle tissue and used during high-intensity contractions. Creatine monohydrate supplementation is one of the most well-researched sports supplements, with consistent evidence for improving short-burst power output and supporting lean mass gains when combined with resistance training. It does not meaningfully affect aerobic endurance. See current research summaries via NSCA or ISSN position stands for detailed context.

DOMS (Delayed Onset Muscle Soreness) - Muscle soreness that peaks 24 to 72 hours after a novel or unusually demanding workout. DOMS is caused by microscopic muscle fiber damage from eccentric loading (the lowering phase of a lift). It is not a reliable indicator of training quality -- an effective session does not require soreness, and soreness without performance gain provides no benefit.

Goal and Outcome Terms

Functional Fitness - Training that improves the capacity to perform activities of daily life -- carrying groceries, climbing stairs, getting up from the floor. Functional programming emphasizes multi-joint compound movements, balance, and mobility. In marketing, the term is applied broadly; in practice, ask any trainer what specific daily tasks their programming is designed to improve.

Corrective Exercise - Exercise programmed to address identified movement dysfunction -- muscle imbalances, mobility restrictions, or compensatory patterns that increase injury risk. NASM's Corrective Exercise Specialist (NASM-CES) credential focuses this specialty. Not all trainers are trained in corrective exercise assessment; it is a reasonable question to ask if you have a history of injury.

Mobility - The ability to actively move a joint through its full range of motion with control. Distinct from flexibility, which is the passive range of motion available in a joint. Mobility is trainable through controlled articular rotations, joint-specific drills, and loaded range-of-motion training.

Flexibility - The passive range of motion available in a muscle or joint, typically measured in static stretching. High flexibility without corresponding strength through the range does not improve injury resilience. Modern training approaches pair flexibility work with active mobility and strength training to produce functional range of motion.

Baseline Assessment - An initial evaluation conducted by a trainer before programming begins. A thorough assessment may include a movement screen, postural analysis, cardiovascular fitness measure, body composition estimate, goal discussion, and health history review. Assessments are important for setting a starting point, identifying contraindications, and giving the trainer enough information to design a safe, individualized program. See how to choose a personal trainer for what to expect from a first session.

Plateau - A period during which training produces no measurable progress despite continued effort. Plateaus occur when training stimulus is no longer novel or sufficient to drive adaptation. They are resolved by changing training variables: load, volume, exercise selection, frequency, or rest periods. A plateau is normal in long-term training and is not evidence that a program has permanently stopped working.

Specificity - The principle that training adaptations are specific to the type of stress applied. Endurance training improves endurance; strength training improves strength; balance training improves balance. Programs are most effective when designed around the outcomes being sought, not built from generic templates.

Recovery - The physiological and psychological processes that restore performance capacity after training stress. Recovery includes sleep, nutrition (particularly protein and total calorie intake), hydration, and rest periods between sessions. Training progress occurs during recovery, not during the workout itself. Under-recovery -- not enough sleep, insufficient calories, excessive training frequency -- limits adaptation and increases injury risk.

Mind-Muscle Connection - The deliberate focus of attention on the target muscle during an exercise, rather than on moving the weight from point A to point B. Research published in the European Journal of Applied Physiology suggests that attentional focus on the working muscle increases muscle activation during isolation exercises. Practical application: slow down, reduce load, and feel the target muscle work rather than compensating with adjacent muscle groups.

For more on how to hire a trainer and what to pay, see the personal trainer cost guide and how to choose a personal trainer.