Overview
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.
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:
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. 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.
Benefits
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.
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.
