The toes-to-bar is a great abdominal exercise for those physically prepared to contend with its demands. And, yes, it might bias the lower portions of these muscles. The toes-to-bar involves resisted and powerful trunk flexion, which undoubtedly works the abdominals. Rectus abdominis (the “six-pack abs” muscle) runs vertically from the underside of the sternum and ribcage to the pubic bone. The fibers of rectus abdominis also run vertically but do not run the entire length of rectus abdominis, because they are interrupted by tendinous inscriptions that create the outline of a chiseled six- (or eight-) pack.  Due to the momentum of the kip and the stretched position of the muscle, rectus abdominis likely experiences peak tension during the rapid eccentric contraction at the bottom of the movement. Eccentric muscle contractions have been shown to elicit preferentially greater muscle growth at the distal end of the muscle in other body parts. (4) Therefore, the eccentric bias of the toes-to-bar could, theoretically, lead to enhanced lower abdominal development over time.  A rationale based on surface electromyography (sEMG) is most commonly cited to support the toes-to-bar (and similar exercises) for “lower abs” training. Leg raises result in greater activity in the lower portion of rectus abdominis than the upper portions. (5) Similar findings have been reported with hanging knee-ups, which are essentially hanging leg raises performed with bent legs. (6) Due to the similarities between these exercises and the toes-to-bar, it is fairly safe to assume that the toes-to-bar, too, electromyographically biases the lower rectus abdominis.  However, surface electromyography is not a valid indicator of the amount of muscle a dynamic exercise activates or will ultimately stimulate to grow. (7)(8) For these reasons, we must be cautious about inferring superior “lower ab” hypertrophy outcomes from toes-to-bar. Keep in mind, toes-to-bar is a very fast movement. Although peak tension in the muscle is likely quite high during the eccentric transition of the kip, the abdominals do not experience prolonged time under tension. Those interested in building muscle may be better served by a more traditional exercise variation, such as the strict toes-to-bar or reverse crunch.