Low back and abdominal exercise regimens are per- formed for a variety of reasons, but mainly for rehabili- tation of the low back, prevention of injury, and as a componerit of fitness programs. The objective of exer- cise is usually to stress both damaged tissue and healthy supporting tissues to foster tissue repair while avoiding further excessive loading, which can exacerbate an exist- ing structural weakness. Certain types of low back inju- ries are characterized by very specific tissue damage and may require quite different exercise rehabilitation pro- grams. For example, persons with a posteriorly herniated disk would do well to avoid full spinal flexion maneuvers, particularly with concomitant muscle activity