The Captain's Chair exercise

The Captain's Chair exercise (vertical knee raise) came in second on the list of best exercises for the rectus abdominus. This is the conclusion of a study at San Diego State University that compared 13 common abdominal exercises in order to find which ones really strengthen the abs. Each exercise was ranked for muscle stimulation (measured with EMG) in the rectus abdominus and the internal and external obliques.

The captain's chair exercise was one of the few ab exercises on the "most effective" list that requires gym equipment. You will generally find a vertical knee raise machine in health clubs, or shop for one designed for home use.