Standard exercise for the central abdominal muscle is the crunch, the starting point for any abs training. The central abdominal muscle does the job of curling the spine, lifting the shoulders off the ground, to create that crunching movement, by shortening and lengthening the muscle. Everything else locked, not using momentum. There are many variations on the standard crunch, but our experts say hand and feet position is mostly a matter of personal preference. Performing a crunch on a decline b