Weight training glossary

Weight training glossary
If you truly want to enjoy the incredible benefits of weight training, it is important to understand key terms, concepts, and principles related to muscle science, nutrition, exercise, and training. Without an understanding of the key terms, concepts, and principles, you will train in the dark, almost certainly make mistakes, fail to recognize false information, and be unable to properly optimize your weight training program.

This weight training glossary lists all of the key terms, concepts, and principles that I think are important for you to know. Making yourself familiar with them will give you an advantage over the people who are unfamiliar with them—which will include most of the people at your gym! To make things easier for you, I have kept the science to a minimum. The terms have been simplified and described in the context of weight training.

Muscle science

Agonist — A muscle that is primarily responsible for bringing about a movement.

Antagonist — A muscle that acts in opposition to the agonist.

Synergist — A muscle that assists another muscle to accomplish a movement.

Stabilizer — A muscle that contracts with no significant movement to maintain a posture.

Concentric muscle action — The shortening of a muscle during contraction.

Eccentric muscle action — The lengthening of a muscle under controlled tension.

Atrophy — The gradual wasting of a muscle that occurs when you stop training.

Hypertrophy — The scientific term for muscle growth.

Metabolism — The physical and chemical processes that occur within cells that are necessary for maintaining life. Metabolism can be divided into anabolism and catabolism.

Anabolism — The constructive metabolic processes that build and maintain body tissues.

Catabolism — The destructive metabolic processes that break down body tissues.

Basal metabolic rate (BMI) — The lowest metabolic rate experienced while an individual is at complete physical and mental rest.

Muscle fiber — One of the cells that make up a muscle. Muscle fibers are cylindrical, multinucleate (have multiple nuclei), and contract when stimulated.

Type I muscle fiber (aka slow-twitch muscle fibers) — Muscle fibers that are used for low-intensity, aerobic activities, such as jogging and lifting light weights. They have high endurance, contract relatively slowly, and do not tire easily.

Type IIa and type IIb muscle fibers (aka fast-twitch muscle fibers) — Muscle fibers that are used for high-intensity, anaerobic activities, such as sprinting and lifting heavy weights. They have low endurance, contract relatively rapidly, tire easily, and can generate relatively high levels of tension.

Fatigue — The decreased capacity or complete inability of a muscle to contract normally caused by prolonged exertion.

Lactic acid — An acid that is produced by muscle tissue during exercise, especially when oxygen supply is limited, and can cause cramping pains.

Motor neuron — A nerve cell that stimulates muscle fibers to contract.

Motor unit — The name for a motor neuron and the muscle fibers that it stimulates.

Neuromuscular adaptation — The adaptations that your motor neurons and muscle fibers experience when you first start training that improve efficiency and strength.

Muscle size — A muscle’s diameter.

Muscle endurance — A muscle’s ability to keep contracting against resistance.

Muscle strength — The amount of force a muscle can produce.

Muscle power — A muscle’s ability to produce both strength and speed.


Nutrition — The study of dietary requirements for proper health and development. Also, the process by which organisms take in and utilize food materials.

Nutrient — A substance that is essential for proper growth and development.

Micronutrient — A substance, such as a vitamin or mineral, that is essential in small amounts for proper growth and development.

Macronutrient — A substance that is essential in large amounts for proper growth and development. The macronutrients are carbohydrate, protein, and fat.

Carbohydrate — Your body’s main source of energy. Three main types are found in foods: sugars, starches, and fiber.

Glucose — A simple carbohydrate and the most important sugar in human metabolism, serving as a primary source of energy. It is absorbed readily into the bloodstream, where it is referred to as “blood sugar”.

Glycemic index (GI) — A measure of a carbohydrate-containing food’s ability to raise blood sugar (glucose) levels after being eaten. All foods containing carbohydrate are ranked on an index from 0 to 100. The GI of pure glucose is 100.

Protein — Complex molecules that play a central role in biological processes and form the basis of living tissues. They consist of chains of smaller compounds called amino acids.

Fat — An important source of fuel for the body made of fatty acids, which also contribute to the structure and proper function of body cells. Essential for the production of the muscle-building hormone testosterone.

Vitamin — Any of various organic substances that are essential in minute amounts for normal growth and activity of living organisms. Found in minute amounts in foods and also produced synthetically. Vitamin deficiencies lead to specific disorders.

Mineral — An inorganic element, such as calcium, iron, potassium, sodium, or zinc, that is essential for cellular metabolism, growth, and development.

Calorie — A unit of energy found in food. One calorie contains enough heat to increase the temperature of 1 g of water by 1 °C.


Aerobic exercise — Low-intensity exercises, such as jogging, that allow most cells to receive adequate oxygen. Aerobic means “with oxygen”.

Anaerobic exercise — High-intensity exercises, such as sprinting, that do not allow most cells to receive adequate oxygen, in which case the cells have to rely on other chemical reactions for energy. Anaerobic means “without oxygen”.

Isolation exercise — Physical exercises that target only one muscle group and involve the movement of only one joint (or one pair of joints). Popular isolation exercises include dumbbell curls, leg curls, and calf raises.

Compound exercise — Physical exercises that target multiple muscle groups and involve the movement of two or more joints (or pairs of joints). Popular compound exercises include bench presses, deadlifts, and squats.

Cardiovascular exercise — Exercises that improve the efficiency of the cardiovascular system (the heart, blood, and blood vessels).


Progressive overload — The gradual increase in the weight being lifted so as to stimulate progressive muscle development.

Repetition or “rep” — One complete unit or movement of a weight training exercise, from the starting position to the point of maximum contraction and then back to the starting position.

Range of motion (ROM) — The full range of motion that a joint is capable of making.

Tempo — The speed at which reps are performed.

Form — The specific technique that should be used when performing an exercise that ensures maximum safety and results.

Training to failure — Performing reps until you can no longer complete the concentric phase using proper form due to fatigue.

One-repetition maximum or “one-rep max” — The heaviest weight you can lift for one, and only one, repetition using proper form.

Set — A group of reps. For example, if you perform ten reps before resting, those ten reps count as one set.

Training frequency — The number of training sessions performed per week.

Training intensity — How heavy the weights are that you are lifting relative to your one-rep max.

Training volume — The number of muscles worked, and the number of exercises, sets, and reps performed in a single session.

Split — The act of dividing the training of muscle groups between days of the week so that you don’t have to train every muscle group in one day.

Periodization — The implementation of specific training phases that involve increasing and decreasing training volume, frequency, and intensity with the aim of both stimulating gains and allowing recovery.

Detraining — The loss of fitness that occurs when you stop training.

Overtraining — Training so much that you experience a decrease in performance or a plateau in results. Usually a sign that training load has exceeded recovery capacity.

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