- stomach

No matter how you analyze it, spins are all about your stomach muscles. Speaking strictly from mechanical physics, three things kill a spin: misalignment of the weight distribution along the vertical axis, a shifting of that distribution off-axis, and precession.

As you practice your spins you tend to naturally compensate for misbalance by thigh and arm adjustments, but the foundation for all of these torque dynamics actually are based upon the position of your hips, your rear end, and the angle you maintain between them and your spine.

And this is all governed by taught, controlled stomach muscles. Are your spins unstable? Sit ups, my dear.