How Isometric Muscle Contraction Works

Is it possible to strengthen a muscle without even moving? An isometric muscle contraction, or static exercise, does just that.

Wall sitting exercise urban outdoor gym in NYC
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In an isometric muscle contraction, the muscle fires (or activates with a force and tension) but there is no movement at a joint.

In other words, the joint is static; there is no lengthening or shortening of the muscle fibers and the limbs don't move.

In this type of muscle contraction, there is no change in the length of the muscle fibers themselves, and there is also no movement at the joints, but the muscle fibers still fire.

A good example of an isometric exercise includes pushing hard against a wall or doing a wall sit exercise (sitting with your back against the wall, knees bend as though you are sitting in an invisible chair). While the muscles are still being activated, firing forcefully, and potentially being stressed, unlike a concentric or eccentric muscle contraction, there is no movement at the joints. 

Other Types of Muscle Contractions

An isometric muscle contraction is one of the three different types of muscle contractions, which are also commonly known as muscle fiber activations.

These occur when a muscle fiber or group of fibers is signaled by the brain via nerves to activate and increase the tension within the muscle, such as during exercise like weight training. The muscles in a human body are made of bundles of muscle fibers that contain thousands of smaller structures called myofibrils, which is where the actual contraction occurs.

The other two types of muscle contractions are:

  1. Concentric Muscle Contraction: In typical weight training exercises, this is the actual lifting phase of any given exercise. Muscle fibers are shortened during concentric muscle contractions and strength is developed.
  2. Eccentric Muscle Contraction: In typical weight training exercises, an eccentric contraction is a phase where the muscle returns to the original starting position of the exercise. During this type of contraction, the muscle fibers are stretched, rather than shortened.

Joint movement does occur in the majority of traditional concentric weight training exercises, such as a bicep curl, squat or a pull-up. Joint movements even occur in eccentric contractions, such as walking downstairs, where the quadriceps lengthen as you lower your self.

In both such exercises, the muscle fibers are firing and there is also movement at the joints. Isometric exercises, in contrast, appear as though nothing is actually happening.


If there is no movement in the joints, is there any benefit to isometrics? As it turns out, there are a variety of good reasons to do isometrics. The main benefit of isometric exercises is that they can be used for rehabilitation as well as general strengthening without placing stress on the joints. This is an important aspect of isometric exercises because exercises that require joint movement can place a lot of stress on individual joints, especially over time with repeated usage.

Isometric exercises are much easier on the joints in both the short term and the long term. They still cause the muscle fibers to fire, without the additional stress on the joints. For this reason, isometric exercises are often used in rehab routines for individuals that have had joint problems or issues.

Another benefit of isometrics is that they can be done anywhere with no equipment. Stuck in traffic? You can tighten and relax your muscles, or press up and down on the steering wheel to get your muscles firing. They are also sometimes recommended for athletes who are in a cast or a boot in order to keep the muscles active while the bones heal.

Some sports require a high level of static muscle strength. Gymnastics, yoga, rock climbing, and downhill skiing, for example, all have static strength requirements. These exercises require a lot of strength, if not a lot of joint movement.

It is important to note that if you feel any sort of joint pain while exercising, you should consult a doctor.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Terada S, Miaki H, Uchiyama K, Hayakawa S, Yamazaki T. Effects of isokinetic passive exercise and isometric muscle contraction on passive stiffness. J Phys Ther Sci. 2013;25(10):1347-52. doi:10.1589/jpts.25.1347

  2. Padulo J, Laffaye G, Chamari K, Concu A. Concentric and eccentric: muscle contraction or exercise?. Sports Health. 2013;5(4):306. doi:10.1177/1941738113491386

  3. Rhyu HS, Park HK, Park JS, Park HS. The effects of isometric exercise types on pain and muscle activity in patients with low back pain. J Exerc Rehabil. 2015;11(4):211-4. doi:10.12965/jer.150224

Additional Reading
  • Fisher JP, Farrow J, Steele J. Acute Fatigue, and Perceptual Responses to Resistance ExerciseMuscle Nerve. 2017 Mar 21. doi: 10.1002/mus.25645. 

  • National Strength & Conditioning Association (NSCA). Essentials of Strength Training and Conditioning, 4th edition. Champaign, IL: Human Kinetics; 2015.

  • W. Larry Kenney and Jack Wilmore. Physiology of Sport and Exercise, 6th edition, Champaign, IL: Human Kinetics; 2015.

By Elizabeth Quinn
Elizabeth Quinn is an exercise physiologist, sports medicine writer, and fitness consultant for corporate wellness and rehabilitation clinics.