The dead but is a good way to learn how to keep your abs braced while your limbs move. Core stability enables you to produce more force as you run, pedal, lift, throw, etc. For runners, the "ribs down" position keeps the upper torso stays stacked over the hips. This is good running posture. This position allows for effective hip extension while running. Keep your low back flat or 90% flat to the ground as you do the exercise. Stay focused and strive for smooth, fluid, coordinated movement.
