Most would assume that knee and leg raise exercises target the lower abs. But when the legs or knees are elevated from a supine position, the hip flexors become the prime movers, not the abs. Thus, alternative exercises are recommended.

It is also important to note that the midsection is not divided into lower and upper halves. The rectus abdominis is one muscle and functions as such. The following are instructions for performing the declined bench reverse ab crunch:

Start by lying in the supine position (on your back) on the declined bench. Grasp the top part of the bench for control and to prevent sliding during the exercise. Slowly bring your knees toward your chest. The knees should travel to at least the 90 degree point or beyond. Slowly lower the knees so that the legs become straight. Repeat the exercise several times.

NOTE: You should breathe out as the knees go up. There are a few variations of this exercise. The first is with the legs extended throughout the entire movement. The second is with the hip elevating completely off the bench as the knees approach the head.