Muscle Growth Glossary: 250+ Fitness & Muscle Building Terms Explained

Muscle Growth Glossary: 250+ Muscle Building Terms Explained

Muscle Growth Glossary

Welcome to the ultimate muscle-building glossary.

Whether you’re a beginner trying to understand terms like progressive overload and hypertrophy, or an experienced lifter researching concepts like mTOR, satellite cells, and muscle protein synthesis, this glossary explains everything in simple language.

This page is designed to become the central resource for fitness, bodybuilding, nutrition, and muscle growth terminology.

Bookmark this page and use it whenever you come across a term you don’t understand.

Jump to Letter

A | B | C | D | E | F | G | H | I | L | M | N | O | P | R | S | T | V

A

Anabolic State

A physiological environment where muscle protein synthesis exceeds muscle breakdown, creating favorable conditions for muscle growth.

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/glossary/anabolic-state/

AMPK

An enzyme that acts as an energy sensor inside cells and can influence muscle growth and energy metabolism.

Androgen Receptors

Cell receptors that interact with hormones such as testosterone and play an important role in muscle development.

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/glossary/androgen-receptors/

B

BCAA (Branched-Chain Amino Acids)

Three essential amino acids—leucine, isoleucine, and valine—that are involved in muscle protein synthesis.

Bulking

A nutrition phase where calories are intentionally increased to maximize muscle growth.

Body Recomposition

Building muscle while simultaneously losing body fat.

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/glossary/body-recomposition/

Basal Metabolic Rate (BMR)

The number of calories your body burns at complete rest.

C

Calorie Surplus

Consuming more calories than your body burns to support muscle growth.

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/glossary/calorie-surplus/

Catabolism

The breakdown of muscle tissue and stored energy within the body.

Creatine

One of the most researched supplements for improving strength, performance, and muscle growth.

Compound Exercise

An exercise that trains multiple muscle groups simultaneously.

Examples:

Squats
Bench Press
Deadlifts
Pull-Ups

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/glossary/compound-exercise/

Cortisol

A stress hormone that influences recovery, energy levels, and muscle maintenance.

D

Deload

A planned reduction in training volume or intensity to improve recovery.

DOMS (Delayed Onset Muscle Soreness)

Muscle soreness that typically occurs 12–48 hours after exercise.

Drop Set

A training technique where weight is immediately reduced after reaching failure.

E

Eccentric Training

The lowering portion of an exercise where muscles lengthen under tension.

Example:

Lowering the bar during a bench press.

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/glossary/eccentric-training/

Electrolytes

Minerals such as sodium, potassium, and magnesium that help regulate hydration and muscle function.

F

Failure Training

Performing repetitions until another good repetition cannot be completed.

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/glossary/failure-training/

Fasted Training

Training after a prolonged period without food, often in the morning.

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/glossary/fasted-training/

Free Weights

Exercise equipment such as barbells, dumbbells, and kettlebells that are not attached to machines.

G

Glycogen

Stored carbohydrates found in muscle and liver tissue that fuel exercise performance.

Growth Hormone

A hormone involved in growth, recovery, and tissue repair.

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/glossary/growth-hormone/

H

Hypertrophy

An increase in muscle size resulting from resistance training.

HMB

A supplement metabolite derived from leucine that may help reduce muscle breakdown.

I

Insulin Sensitivity

How effectively the body responds to insulin and transports nutrients into cells.

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/glossary/insulin-sensitivity/

Isolation Exercise

An exercise that primarily targets one muscle group.

Examples:

Bicep curls
Leg extensions
Tricep pushdowns

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/glossary/isolation-exercise/

L

Lean Bulk

A muscle-building phase designed to maximize muscle gain while minimizing fat gain.

Lactic Acid

A byproduct associated with intense exercise and muscular fatigue.

M

Mechanical Tension

One of the primary drivers of muscle growth created by resistance against muscle fibers.

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/glossary/mechanical-tension/

Muscle Protein Synthesis (MPS)

The process of repairing and building new muscle proteins.

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/glossary/muscle-protein-synthesis/

Muscle Memory

The ability to regain lost muscle faster than it was initially built.

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/glossary/muscle-memory/

mTOR

A cellular pathway involved in regulating muscle protein synthesis and growth.

Metabolic Stress

Muscular stress created by high repetitions, pumps, and metabolite accumulation.

Read More →
/glossary/metabolic-stress/

Macronutrients

The three major nutrients required by the body:

Protein
Carbohydrates
Fat

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/glossary/macronutrients/

N

Natural Lifter

An individual who builds muscle without using performance-enhancing drugs.

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/glossary/natural-lifter/

O

Overtraining

A prolonged state of excessive fatigue and impaired recovery.

P

Progressive Overload

Gradually increasing training demands over time to stimulate muscle growth.

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/glossary/progressive-overload/

Protein Synthesis

The biological process of creating new proteins within the body.

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/glossary/protein-synthesis/

Progressive Resistance Training

A structured training approach that gradually increases difficulty.

Read More →
/glossary/progressive-resistance-training/

Pre-Workout

A supplement designed to improve workout performance and energy.

R

Reps in Reserve (RIR)

The estimated number of repetitions you could still perform before reaching failure.

Rate of Perceived Exertion (RPE)

A subjective scale used to measure training intensity.

Recovery

The process by which the body repairs and adapts after training.

S

Satellite Cells

Cells involved in muscle repair and growth.

Read More →
/glossary/satellite-cells/

Sarcoplasmic Hypertrophy

An increase in muscle size resulting from increased fluid and glycogen storage.

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/glossary/sarcoplasmic-hypertrophy/

Superset

Performing two exercises consecutively with minimal rest.

T

Testosterone

A hormone that plays an important role in muscle growth and recovery.

Time Under Tension (TUT)

The amount of time muscles remain under load during an exercise set.

Read More →
/glossary/time-under-tension/

V

Training Volume

The total amount of work performed during training.

Often measured as:

Sets × Reps × Weight.

Read More →
/glossary/training-volume/

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