The Next Page: F=ma (or bringing the heat)

On the eve of the Pirates' new season, baseball fan and anatomist Chuck Welsh reveals the secrets of good pitching


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I played baseball competitively from grade school until I was a teenager (from 1971 to 1979, the period between the Pirates' most recent World Series victories).

By the time I was in high school, the pitches were too fast and traveled in vectors that did not afford me much opportunity to make contact. I wanted to maintain a competitive edge, so I tried switching from second base to pitching. My linear, mid-speed pitches however, were eminently "hittable."

In one memorable inning, I pitched for the cycle -- giving up a single, double, triple and home run. I obsessed over why I could not throw a 90-mph fastball or a breaking ball that could make a fool out of the opposing batter. Would it have helped me to be taller or to have had a longer arm? Or maybe to have gotten more push off of the mound with my legs?

I am now of the age where many of the Major League Baseball players are young enough to be my sons. And after the Pirates ended a 20-year dry spell last year, making it to the first round of the post-season in large part on the strength of their pitching, my teenage obsession partially has morphed into middle-age analysis.

What does it take to pitch in the major leagues?

The simple answer: a strong arm. To be sure, this is true. But it's neither the absolute nor whole truth. Any National Football League lineman has improbably strong arms. As do Arnold Schwarzenegger and Sylvester Stallone.

Strength is a relative term. Bench-pressing and bicep curls, weight-training staples, involve moving a great amount of weight a short distance. Bench-pressing primarily is brought about by the action of two large muscle groups: the triceps in the arms and pectoralis muscles in the chest. Bicep curls are named for the action of the biceps in the arms. These are decidedly isolated events whereby the muscles of the chest and arms generate the traditional type of force associated with muscle contraction. The more force (power) generated, the more resistance (weight) can be displaced (moved).

Gyms are full of 250-pound guys who enjoy such competition. But most of them could not throw a 90-mph fastball like San Francisco Giants ace Tim Lincecum, who, soaking wet, weighs about as much as a ninth-grade basketball player.

To throw a baseball with great speed, whether pitching or gunning down a runner from the outfield like Andrew McCutchen does and the great Roberto Clemente used to do, a person needs more than arm muscles. Lifting weights actually could have deleterious effects on a pitcher's mechanics.

Isaac Newton, whose intellect is thought to have been second only to Albert Einstein's in the pantheon of great scientists, worked all this out in his seminal three laws of motion. To those who took college physics, I am sorry to dredge up old memories of vectors, gravity and electromagnetism.

Today, as an amateur historian of science, I am thankful for and fascinated by Newton's laws. But if time travel had been possible when I was a college sophomore, I gladly would have returned to the late 17th century to tear out various pages from Newton's notebook. I would have used them for kindling to keep his study warm until he figured a simpler, non-calculus way to describe the universe. But his underlying points are fairly straightforward and serve our present inquiry well.

The first law: A body stays at rest or moves with constant velocity unless acted upon by an external force. This law helps describe the actions of weightlifting. The weights remain stationary until muscles generate a force sufficient to move them.

The third law: When a body exerts a force on a second body, the second body exerts an equal-yet-opposite force. In short, force is a two-way street. This is of particular interest to bodybuilders. While muscles generate a force to move weights, the weights push back on the muscles. This stress on the muscles and associated tendons stimulates muscle cells to grow larger.

But Newton's second law holds the key to understanding the generation of forces in throwing and pitching. It's immortalized in this formula: F=ma. That is, a force generated is equal to the mass (synonymous with weight for our purposes) of an object multiplied by its acceleration (changes in speed over time).

The force (F) is generated by the pitcher's body, and the mass (m) is the weight of a baseball (5 to 5.25 ounces).The ball leaves the pitcher's hand with an acceleration generated by the pitcher's body but then travels with a certain acceleration, or deceleration, based upon other external forces, such as gravity, friction, wind and even humidity (a). That is, the velocity upon release is almost never the same as the velocity the ball has when it crosses the plate. If we isolate acceleration in the equation, we get a=F/m. The more force you generate, the faster the ball moves.

Generating such a force in pitching has almost nothing to do with the strength generated by weightlifting. It's related to the kinetic chain, the swift transfer of momentum from one body region (segment) to another.

Here is the kinetic chain for pitching:

Windup-stride/early cocking: These position the body for maximum momentum and velocity. The leg opposite the throwing hand is elevated. The ball is taken out of the glove, and the arm begins to move backward.

Late cocking and acceleration: The arm is brought back as far as it can go, and the foot comes to the ground. The arm is brought forward rapidly to release the ball.

Deceleration: This phase -- with the ball released and elbow extended -- involves a fair amount of traditional muscle contraction in the shoulders and arm, including the biceps. So it seems that lifting weights does not contribute to pitch speed but helps with stopping the motion, preventing the pitcher from falling over.

During these phases, the hips are also rotating. The momentum is transferred from the legs and hips to the torso, then to the shoulder and down the arm to the ball. To fully appreciate this, try to throw a ball standing still using only your arm. Then try it again taking a step forward. The latter will launch the ball farther and faster.

Softball pitchers and NFL quarterbacks cannot generate the same speed as baseball pitchers because their throwing motion excludes most of the hip rotation. Softballs and footballs also weigh more than baseballs.

Almost anyone can wind up and throw a ball. But why can some throw with such speed? That is, why can some harness the power of the kinetic chain better than others?

Genetics! We are built as differently on the inside as we are on the outside. It does help to have long legs and arms for maximum momentum. But also important are variations in muscle size and shape and the attachment of the tendons to the bones at slightly different locations and angles.

A region in the back of the brain called the cerebellum, which houses about 50 percent of all nerve cells, coordinates all muscle contractions and body movements. This has a great deal to do with athletic ability in general and with keeping certain muscle groups stable throughout the pitching motion.

The key to a fastball is quick motion and stability. Lots of MLB pitchers are not noted for fastballs as much as breaking balls and change-ups intended to fool batters with movement.

The fine control needed in the arms and wrist for these is also a product of the cerebellum. The Pirates' Jason Grilli excels at speed and breaking balls. Other examples of athletes with extraordinary cerebella are the Penguins' Sidney Crosby and the Miami Heat's LeBron James. Their performances on the ice and the court, respectively, are nothing short of elegance.

Swinging a golf club employs the same principles as pitching. Rotating the hips while swinging transfers the momentum to the end of the club. I sadly report that I golf about as well as I pitch.

And my eldest son will never make the tour either. As he shanked one drive so far right that it almost boomeranged back to us, he screamed, "Thanks for the genes, dad." He then threw the driver farther than the ball usually goes.

Ironically, Newton's laws of motion and gravity could just about pinpoint where it would land.

Chuck Welsh (welshc@duq.edu) is an assistant professor of biology at Duquesne University who teaches anatomy and physiology to students pursuing health-related careers.


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