Softball Bat Speed

Editors Note: The issue of bat speed has long been debated. To help us better understand the theory behind bat speed, we’ve asked Jack Mankin, head of Bat Speed, Inc., who has undertaken considerable research on the topic, to give us in layman’s terms a better understanding of the issue.In the coming weeks, additional installments from Bat Speed will be posted. Your views on the subject are of course encouraged. --NSSF Editor.

Mechanics that Generate Bat SpeedMany tests have shown that rotational mechanics are far more efficient than linear mechanics in developing bat speed. In order to understand why this is true, it is important to understand the forces acting on the bat.
Other than the effects of gravity, drag (due to airflow) and other minor factors, there are two forces acting on the bat that create bat speed: Circular Hand Path (CHP) - The transfer of the body's rotational momentum that occurs when the hands are taken in a circular path.Torque - Torque is applied at the handle of the bat by the push/pull of the hands/arms/shoulders.Circular Hand Path The bat will undergo angular displacement (i.e., bat speed) when the path of the hands is also undergoing angular displacement (i.e., a circular hand path). In other words, as long as the path of the hands stays in a circular path as the body rotates, the circular hand path will transfer the body's rotational momentum into bat-head acceleration.
In technical terms, we often refer to bat-head acceleration generated from the CHP as the"Pendulum Effect" so as to distinguish it from the "Crack of the Whip" theory. (We'll take a brief digression to better explain this topic.) A pendulum is simply an object that swings freely back and forth in a circular arc (i.e., pendulum clock). However, in the baseball swing, there are two pendulums: 1) the lead-arm swings the hands in a circular arc, and 2) the end of the bat swings around the hands. This is referred to as the Double Pendulum Effect of a CHP.
A double pendulum consists of one pendulum attached to another. (To see an example of the Double Pendulum Effect of a CHP, Linear mechanics is much different in that it does not rely on a circular arc (or Pendulum Effect), as it is based on a theory that when the hands are extended in a straight line, the bat-head will suddenly accelerate to contact like the crack of a whip ("Whip Effect".) However, this theory is flawed since there is no whip effect in the baseball swing (a bat is not flexible like a whip), and consequently, efforts to produce a whip effect has stalled many hitters progress for decades.
A substantial portion of a good hitter's bat speed is derived from the circular path of his hands (think of swinging a ball on the end of a string). As long as we keep our hand in a circular path, the ball will continue to accelerate in a circle. However, if the path of the hand straightens, the ball on the end of the string loses angular velocity and trails behind the hands.
The same rational applies when a hitter is swinging a bat. If the hands are kept in a circular path, the bat will continue to accelerate. But if the hands straighten, the batter loses the circular path and the bat will lose speed. With a straighter hand path, the bat-head trails behind the hands well into the swing. This is often referred to as "knob of the bat first" and results in poor bat speed.
Torque is the result of two forces being applied to an object from opposing directions that cause the object to rotate about a point. Forces in the same direction may cause the object to accelerate, but will not cause the object to rotate about a point (no angular displacement). For example, when loosening a lug nut with a 4-prong tire wrench, you push down with one hand while pulling up with the other (torque). However, if you push down (or pull up) with both hands, you would not cause the nut to rotate (no torque).
Torque is applied in the swing by the push/pull action of the forearms and hands. The bat-head is accelerated from torque when the direction of force applied by the hands is from opposing directions.
To reach maximum bat speed, the batter must apply torque from initiation to contact and keep the hands in a circular path. Average hitters' usually have very little circular hand path in their swing (no pendulum effect) due to the straighter hand-path. As a result, average hitters rely mainly on torque to accelerate the bat-head. (Remember, there are only two forces acting on the bat - a circular hand path and torque. If one of the forces is missing, the batter will have to rely on the other force to move the bat.)
For a batter to attain his maximum potential, his mechanics must make efficient use of both - CHP and torque. Great hitters generate great bat speed because their swing mechanics efficiently apply torque at the handle that compliments the their circular hand path.
--Jack Mankin, Bat Speed, Inc.
Next installment: "Rotation and the Stationery Axis"