Performing this exercise is similar to doing a leg crunch except that the legs are straight up, forcing the abs to work and adding intensity to the routine. To do this, lie on the floor with the legs straight up, knees crossed, and place the hands beneath the head for support. Contract abs lifting the shoulders off the floor and keep legs in a fixed position to crunch. Do 1 to 3 sets with 12 to 16 repetitions.

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