Today’s CrossFit.com Workout of the Day features GHD sit-ups. The primary benefit of the GHD sit-up is to develop the core musculature strength to prevent movement of the spine in a high-force/high-velocity setting. The static contraction of the abdominals is more potent than the dynamic one seen in crunches. However, the spine does not remain completely static throughout the movement; there is some flexion and extension: The athlete extends slightly past neutral at the bottom to take the trunk