MARSHALLING FORCES

To the Editor: I read the article on the kinetics of pitching (“Coached by Newton,” April 2009) with great interest, as I have a damaged shoulder and I can relate to much of what is contained in the piece.

My problem is Canada geese nesting on our pond. It’s not that they take up residence there, but that they intimidate my domestic ducks, so I have taken to throwing rocks in their general direction to make them go play somewhere else. I discovered a conventional throw, much like a baseball pitch, causes a great deal of pain, so I have reverted to my early life when I used to play cricket, and use a straight arm bowling action—also advocated by the military, by the way, as a pain-free method of delivering hand grenades.

Then your magazine arrived and the article about Mike Marshall contains stop action footage showing exactly the straight, overarm action used for many years in easy cricket ball and hand grenade deliveries.

It is true there is not much new under the sun.

DOUGLAS L. MARRIOTT
SOUTH LEBANON, OHIO

To the Editor: Thanks ever so much for helping to perpetuate Mike Marshall’s absurd fantasy that his pitching motion theories are scientifically grounded. Despite having won a Cy Young award in his time, and despite having been awarded a Ph.D. in exercise physiology a long time ago, Mike Marshall has for years completely denounced the pitching mechanics that made him good in the 1960s and 1970s.

Instead, he has crafted an absurd new pitching delivery that he claims is “100 percent guaranteed to be injury-proof and at the same time allowing pitchers to compete at the highest levels of baseball.” His Web site is filled with such bunk.

Dr. Glenn Fleisig of the American Sports Medicine Institute performed a careful and detailed motion analysis study of four hand-picked Marshall pitching students. He compared the Marshall pitchers and their mechanics to two different groups: (1) elite college and pro pitchers who were matched by age and size with the Marshall group and, (2) a velocity-matched group who were also matched by age and size with the Marshall group.

Dr. Fleisig’s published conclusion was that Marshall’s mechanics generated more stressful forces on the elbow and shoulder of his pitchers than the traditional pitching motion, while generating less pitching velocity. A true lose-lose situation.

Now, I don’t have any idea how seriously engineers and scientists may take your Web version, but I assure you, publishing Mike Marshall’s foolish assertions without peer-review or critical analysis won’t help your reputation any.

LEE A. FLIPPIN
SAN FRANCISCO, CALIF.

Editor’s note: A summary of results of Glenn Fleisig’s study is available online at http://asmiforum.proboards.com/index.cgi?board=general&action=display&thread=608. Mike Marshall’s article, “The Three Laws of Force Application for Baseball Pitchers,” is an ME Online Exclusive for April 2009 at www.memagazine.org. Fleisig was interviewed for a companion article, “Engineering Baseball,” also available online.

To the Editor: In the article by Steven Kerno on the mechanics of a pitched baseball, the author has omitted a key element: all pitchers, except knuckleballers, release the ball with a great deal of spin. Thus some of the energy supplied by the arm’s force must go into the ball’s rotation, leaving less available for linear velocity.

The author acknowledges omission of this element when he states, “the forces that act upon a baseball after it is released—downward gravitational force and air resistance.” The ball’s rotation creates another force, usually referred to as the Magnus effect. This is what makes curve balls curve and fastballs rise.

It would also have helped if diagrams were included in the article to help explain the principles.

MAURICE BLUESTEIN
POMPANO BEACH, FLA.

To the editor: The article “Coached by Newton” was fascinating and praiseworthy.

Nevertheless, there was a serious omission. In the discussion, it was in effect assumed that the mass of the baseball (about 5 ounces or 0.146 kg) is the only mass to be accelerated by the thrower. The mass of the thrower’s hand and arm was ignored altogether.

To do a very crude check, I put my hand on a postal scale, while supporting at the elbow with my other arm. As it is difficult to go totally limp, the result is not very accurate. It was in the range of 4 to 5 ounces, about the same as the mass of a baseball.

The mass of the thrower’s arm, and indeed of the rest of the body, can reasonably be only ignored in case of heavy events, such as shot-put, or caber toss as in Highland Games. The other extreme, throwing a pebble of negligible mass, has essentially all the thrower’s energy going into accelerating his throwing arm and hand.

All significant effects need to be considered.

ANDRES PEEKNA
WATERFORD, WIS.

EVERY BREATH YOU TAKE

To the Editor: The article “Carbon Loaded” (April 2007) has intrigued me for some time, because I wondered how the CO₂ emissions that were portrayed compared with the human population’s exhalations. None of the articles in the media address that question.

I recently got motivated enough to figure it out. One adult human puts out about 1.2 liters of CO₂ per minute at light work, which equals 1.374 tons per year. Since we sleep one third of the time, and rest half of the awake time, round that off to half a ton per year. If the U.S. population is somewhat over 300 million, then we can say that people are exhaling 150 million tons per year. The total represented by a chart with the article is 7.26 billion tons of CO₂ per year, if I read it right.

Derived from a 2007 U.S. EPA report, this chart breaks down the annual U.S. emissions of greenhouse gases by source. Each of the 726 squares represents the equivalent of 10 million tons of CO₂.

A paper, “The Human Carbon Budget,” published by Springer (http://www.springerlink.com/content/k2676q72n6802084/) contains these estimates: “In 2000, an estimated 17.2 Tg C were consumed by the U.S. population and 15.2 Tg C were expired to the atmosphere as CO₂.” 15.2 Tg is just under 17 million tons of carbon, which converts to more than 61 million tons of CO₂ per year. Let’s assume more detailed analysis would give a number between 61 and 150 for yearly human CO₂ exhalation.

Since humans might already be globally emitting the same order of magnitude of CO₂ as all of their mechanical and agricultural activities combined, it looks like we should give equal effort to reducing human CO₂ emissions as we give to other sources. How about recommending one child per family for a while? Or, stunting body growth by whatever means?

Practically speaking, focusing a lot of effort on any but the biggest four blocks on that chart looks like a waste of resources if population control is not feasible. A friend suggested planting a tree for every child born.

DOUG CULY
TEMPE, ARIZ.

CORRECTION

Due to an editing error, a picture on page 30 of the July 2009 issue was misidentified. The picture showed controllers during the unmanned SA-6 mission, not Apollo 6.