A long arm crunch is an abdominal exercise used to strengthen the upper portion of the abdominal muscles. Done properly, this exercise focuses on working only the abdominal muscles, and will not strain the neck or back. Consistent abdominal pressure is the key to this movement.
The starting position for a long arm crunch is flat on one's back, with the knees bent and the feet flat. Both arms should be extended above and slightly behind the head, and the hands should be held close together. To perform the exercise, the abdominal muscles are contracted, bringing the shoulder blades off of the floor. Once at this point, the body should be lowered back down to the starting position.
During the exercise, the arms should remain next to the ears. They should not fall forward and away from the head. The reason for this is to limit the extent to which other muscle groups, other than the abdominals, are used. Throwing the arms forward can grant extra momentum, undermining the effectiveness of the movement. Similarly, straining with the neck or head to raise the trunk of the body should be avoided.
According to a 2001 study commissioned by the American Council of Exercise (ACE), the long arm crunch is sixth in the list of top ten most effective abdominal exercises. The results were measured using the traditional crunch as a baseline. A traditional crunch is the same as the long arm crunch, except that the arms are not extended and the hands are placed behind the head.
This study designated the amount of muscle activity produced during a traditional crunch as 100%. Other abdominal exercises were compared to it to see if the muscle activity produced was more or less. The long arm crunch produced 19% more muscle activity than a traditional crunch. An exercise known as the Captain's Chair was ranked at the top of the list, with 131% more muscle activity.
As with any abdominal exercise, the long arm crunch relies on slow, controlled movements. The abdominal muscles should be tightened or engaged in order to make the upper body move. Often, other parts of the body, such as the arms or head, are used to try and begin the movement. This limits the effectiveness of the exercise, and could cause injury over time. Properly done, this exercise requires very little movement up and off of the floor in order to produce an effective workout of the abdominal muscles.