Muscle Strength and How to Measure It

Learn How to Test Your Muscle Strength

Young man doing lunges with dumbbells in gym in garage
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Muscular strength is one of the five key components of physical fitness. Strength is defined as the maximum force that can be developed in a muscle or group of muscles during a single maximal contraction. An example would be the heaviest weight you can lift in a bicep curl with good form.

What Determines Muscular Strength?

When you think about how strong you are, there are several components that have to work together.

When you lift a weight or push a load, more is involved than simply having big muscles. The physiological strength of a muscle is influenced by how big it is, the cross-sectional area, but also the types of muscle fibers in that muscle, fast twitch or slow twitch.

Next, the muscle needs a strong neural connection, as the motor neurons must fire to cause muscle contraction. They have to fire in a coordinated way, so more of the muscle fibers are triggered at once. You also need to be able to use that muscle efficiently to move a joint, and that means having healthy and strong joints, bones, ligaments, and tendons.

Other muscles work to assist and oppose the action of a muscle so it is controlled. Posture and positioning are critical for being able to exert the force of the muscle to maximum effect. A small shift one way or another can make a big difference in the amount of strength that can be exerted.

Training to build muscle by lifting and pushing weights, using correct form, will build muscle strength. Not only does strength training exercise build muscle fiber, it also trains the nerves to fire in a coordinated way to move the muscle, and you learn the right form for using the muscle.
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How Is Muscular Strength Tested and Measured?

Repetition maximum testing is the standard for measuring muscle strength. It is abbreviated as 1RM. To do a repetition maximum test, Kramer and Fry (1995) established a protocol that is widely used. The bench press and the leg press are most often tested for determining upper body and lower body muscular strength. You can check your performance against bench press standards compiled by Dr. Lon Kilgore.

To do a 1RM test, you would warm up with a weight you estimate to be about half of the maximum you could lift in the exercise, for 5 to 10 repetitions. Then you take a brief rest and add weight to bring it up to a load you can lift three to five times, at about 75% of maximum. Now you add a small amount of weight and lift it once. If you can lift that with good form, wait three to five minutes, add more weight and try again. You repeat this sequence of adding weight, attempting the lift, and resting until you reach the maximum, and you can't lift the next incremental weight with good form.

Strength measurement in physical therapy and rehabilitation uses a simpler method of opposing a pressure. It is used to grade whether a muscle is functioning normally or not.

The therapist can also use a dynamometer to measure the strength of a specific muscle.

Components of Physical Fitness

The other components of physical fitness are muscular endurance, cardiovascular endurance, flexibility and body composition.


Kraemer, W. J. & Fry, A. C. (1995). Strength testing: development and evaluation of methodology. In P. Maud & C. Nieman, D.C. (1995). Fitness and sports medicine: A health-related approach (3rd ed.). Palo Alto, CA: Bull Publishing.