There are three types of contractions that muscles can perform. These are Eccentric, Concentric and Isometric. Each one refers to the action of the muscle.
- Eccentric contractions are where the muscle contracts while the fibres are lengthening.
- Concentric contractions are where the muscle fibres contract while they are shortening.
- Isometric contraction is when force is being applied in a situation where the muscle fibre neither shortens or lengthens. The joint is generally in a fixed position when this occurs.
There are also some scenarios where the rate of lengthening or shortening is slowed to a point where it can become quasi-isometric in nature. This resembles the type of slow grind that can be experienced when performing near maximal lifts.
Isometrics are useful in training as quite a lot of force can be applied in a relatively safe way. The high forces require an extremely large neural input. It can be a great way to train the neural aspect of strength. In addition it can prepare muscles and tendons to tolerate very high forces which may occur suddenly during sport. This makes isometric training quite an effective injury prevention strategy.
While there are benefits to training with isometrics it can be difficult to perform safely. Certain equipment may be necessary in order to effectively perform a movement isometrically. It also requires some experience of lifting in order to breathe appropriately. Because you must maintain a valsalva or “Bracing” position for a prolongued period there are some risks associated. People with high blood pressure or who may be prone to fainting should avoid such types of training.
Performing these types of movements is relatively simple for the experienced lifter in an adequate facility. Take for example a squat movement. The athlete should set the spotter pins above the bar at an appropriate height (1/4 squat depth etc) with safety bars just below. Using proper technique they simply squat the bar until its path is impeded by the spotter pins. They should continue to exert as much force as they can for a prescribed time. Because they are squatting against a “fixed” bar they wont need to the load the bar as load is now redundant.
Isometrics can be a useful tool in an athletes training method arsenal. While it should be utilized by experienced lifters, certain applications and variations can be utilized by other athletes also. Used in an efficient training program isometrics can be effective in improving strength levels and preventing injury.