Optimizing the Kinetic Link in the Baseball Swing

Presented at The Health, Physical Education and Recreation State Conference
Biloxi, MS\
2000
Chris Yeager, Ph.D., CSCS

How do you generate power when hitting a baseball.

Science made practical and easy for you to understand on how to create energy from your body to the bat head to the baseball.

We can use the example of a bullwhip.

What causes a bullwhip to “CRACK!”???
The tip of the whip travels at 1116 feet per second or 750 mph and breaks sound barrier!
Crack of the whip occurs when all parts of the whip but the tip of the whip has stopped – scientifically, this means that all parts of the whip have decelerated and all of the energy has been transferred to the tip of the whip.

To understand this process one must first understand Momentum:
All moving objects have momentum.

Momentum = mass * velocity

Second, one must understand the Conservation of Momentum.

Momentum is conserved in a collision or defined system:

MASS* VELOCITY = MASS * VELOCITY
(BEFORE) (AFTER)

If mass is lost in a defined system, then velocity must be gained! (in the absence of outside forces)

Conservation of Momentum is the 1st part of the Kinetic Link.

Think of the whip as having different segments like your body.

Your body is built like a bullwhip; the distal parts of the human body are composed of successively smaller and smaller masses – these smaller masses are your wrists and hands.

Throw-like movements (kick – golf – pitch – pass – swing) – sequence the segmental rotations from most massive to least massive or most stable to most free (used for maximum velocity generation). This means:

• Your legs should represent the arm segment of whip system when swinging a baseball bat.
• Your upper body( arms, wrists, hands) should represent the “loose” whip segment.

The arms serve mainly to TRANSFER energy of the body’s rotational and transverse motions to the bat. Your arms add very little extra energy to the system.

The Kinetic link passes momentum from the large base segments(legs, lower body) to the smaller adjacent segments(arms, wrists and hands, upper body).
The kinetic link for hitting a baseball is as follows:

GROUND – LEGS – HIPS – TORSO – SHOULDERS – ARMS – WRIST – Hands

An immature pattern uses fewer segments working simultaneously in a limited range of motion. An immature pattern will limit the amount of energy transferred to your bat head and ultimately to the baseball.

The 2nd part of the Kinetic Link is the elastic reflex or the stretch shorten component.
Muscles contract more forcefully if they are 1st put on stretch.

Elastic energy is the ability to do work while an object recoils or reforms after being STRETCHED, COMPRESSED or TWISTED. This is also considered Potential energy because it is stored and held in readiness.

Examples: The vertical jump, as well as running, creates chemical and elastic energy.

The rate of stretch (rapid) and timing of contraction (short time delay) affect the body’s muscles’ ability to create and use energy.

Kinetic Link Summary – 2 parts: 1. conservation of momentum and 2. elastic reflex

ENERGY = FORCE * DISTANCE