An abdominal crunch or simply a "crunch" is an exercise which is designed to strengthen and tone the abdominal muscles. This exercise is very easy to do at home, and people who perform exercise at home often like to integrate crunches into their routines. In addition to the basic abdominal crunch, it is also possible to perform what is known as an oblique sit up, a variation on the crunch which uses slightly different muscles.
In an abdominal crunch, the body is slowly curled upwards from a prone position, with the abdominal muscles doing the work. This contributes to the development of a strong core, which promotes good posture and reduces the risk of injury. It also strengthens and tones the stomach muscles. For people who are concerned about the appearance of the stomach, one of the big advantages of abdominal crunches is that they tend to trim down the waistline and stomach area, creating more definition and smoother lines in tailored garments.
To perform a crunch properly, someone must lie flat, with the knees bent and the feet placed flat on the ground, hip-width apart. The hands can be loosely placed behind the head or along the sides of the head, or rested on the chest. Then, the exerciser takes a deep breath, pulling the belly button down towards the floor in the process, and slowly curls up on the exhale, keeping the feet and pelvis on the ground. If the hands are placed behind the head to support the neck, they should not be used to pull the head forward.
Once someone has crunched up as far as possible, which may not be very high for people just starting out with crunches, the position is usually held for a moment before the body is slowly lowered back to the ground. After coming to a complete stop, the exercise can be repeated. In the oblique sit up, the legs are bent and placed to one side, and the exerciser crunches as he or she would normally, switching sides halfway through to work the muscles on both sides of the body evenly.
There are some caveats to keep in mind when performing an abdominal crunch to make sure that the exercise is safe and productive. It is important to avoid pulling on or straining the head during crunches, and the chin should be kept up and out; if the chin is touching the chest, this can cause strain. Exercisers should also avoid the temptation to use the momentum of their bodies to propel themselves while doing crunches, as this makes the exercise less effective, and it can cause strain or injury.