November 4, 2011 by Gary McCoy
Almost all human motion in sport and exercise involves rotation or what is called ”Angular motion”. Angular motion can occur with any movement of a body segment about it’s proximal joint.
A rotating body will continue to turn about its axis of rotation with constant angular momentum unless an external torque (moment of force) acts upon it. The magnitude of the torque about an axis of rotation is the product of its force and its moment arm, which is the perpendicular distance from the axis of rotation to the line of action of the force(1)
Most sports – depending upon the skill required- have differing – whole body proximal axis points. A great example of this is the skill differentials in both baseball and golf.
While the two look similar Hitting a baseball and hitting a golf ball the difference becomes clear and exists in the “Axis” of rotation.
A golf ball is struck in the center of the body with rotation beginning at the completion of hip forward translation. The functional axis is more body centered than in the act of hitting a baseball.
The baseball swing- conversely- has an axis point of the front leg- and directly just inside the front hip at the point of maximal power, which is inherently creates greater torque due to an increased moment arm at that segment (the entire length of the pelvic carriage vs. 1/2 the distance required in golf) through to ball contact.
Hip Torque- when measured parellel to shoulder (clavicular line) Torque will provide some interesting skill guidance in maximizing baseball power. The “power slot” will be that point of maximal pelvic and clavicle line torque which will provide the highest rate of implement (bat) speed.
Torque is an important measurement characteristic in understanding athlete performance. Generating higher levels of torque directly correlates to greater power production baseball- but has been rarely measured in rotation due to the lack of tools available for precise measurement.
(1) Introduction to sports biomechanics: Analysing human movement patterns By Roger Bartlett