When a diver flexes his or her head and tucks the limbs before making a dive, he or she reduces his or her moment of inertia. Moment of inertia is defined as the mass distribution around an axis of rotation. Since the diver draws his or her mass closer to the axis of rotation, he or she reduces the distribution. This is important in executing rotations properly during the dive.

This process involves the conservation of angular momentum. In the absence of an external torque on a system, the angular momentum is constant. By reducing the moment of inertia, the diver automatically increases their angular velocity, allowing for faster rotations. This technique is necessary to complete complex aerial maneuvers such as somersaults and twists within the short time available in the air.

Before diving, the diver tucks into an acock position so that rotation can take place rapidly, but at close proximity to the water edge, they extend their body, increasing the moment of inertia in order to bridle the speed of rotation, allowing for entry into the pool safely and precisely while minimizing splash and inflicting damage. This way, bending the head and body is essential for divers to achieve maximum rotational motion and execute complicated maneuvers with great accuracy.

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