M6 Rotational Movement

Topic

In general, the athlete's rotational movement encompasses actions such as a somersault, a jump with a twist, a throw involving trunk rotation, or a spin performed during figure skating.

The fundamental principle underlying this rotational movement is the conservation of angular momentum—a concept established in another model within this set—which applies when no net external torque acts on the athlete, whether during the flight phase or while rotating around a frictionless axis. Consequently, the athlete reduces their moment of inertia by drawing their body segments toward the axis of rotation—a reduction also described in another model in this set—thereby proportionally increasing the final angular velocity of the spin.

In contrast, during a discus or hammer throw, the implement's final tangential velocity at the moment of release determines the throw's final distance; this release point is a factor also addressed in another model in this set regarding throwing precision.

Furthermore, the gyroscopic precession of a thrown ball—such as an American football or a rugby ball—explains its stability during the flight phase.

Thus, regarding the various types of rotational movement introduced here, this model shows that when an athlete spins on the ground, the frictional torque exerted by the ground determines the spin's final deceleration. The final moment of inertia for each of the athlete's body segments is calculated using Steiner's theorem (also established in another model in this set), while the athlete's maximum final angular velocity is limited by both joint stiffness and neuromotor coordination—specifically the neuromuscular coordination addressed in another model in this set regarding neuromuscular control. The fact that this athlete’s joint stiffness is even greater means that, consequently, the final maximum angular velocity achieved during any of the rotational movements introduced at the beginning of this model is even more limited.

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