Extra size and strength equals extra bat speed.
Robert Adair wrote the book on baseball physics. Literally. His "The Physics of Baseball" has enjoyed multiple editions and is considered the classic text in its field.
On page 139, Adair provides an equation relating bat speed (that is, the speed of the bat's sweet spot at the moment it makes contact with the ball) to player weight:
V = k sqrt(M/(m+M/81))
(Note: V is the velocity of the bat in miles per hour, m is the bat weight in pounds, M is the player's weight in pounds, sqrt means square root and k is a constant, 10, in mph. Phew!)
According to Adair's formula -- and don't worry, we asked him to double-check the calculations, since our last math class came in high school -- the 206-pound Bonds generates a bat speed of 67.34 mph, while the 228-pound Bonds swings the same 32-ounce bat at 68.81 mph, an increase of 1.48 mph.
Trust us: That's more impressive than it sounds.
Bat speed is the key to power hitting.
Jack Mankin is an electrical engineer. He also is a youth baseball coach and something of a baseball swing junkie.
Way back in 1986, Mankin bought a VCR that featured frame-by-frame replay, a rare and exotic luxury at the time. He taped about 100 major league games, then set out to chart the swing mechanics that separated great hitters from average ones.
Mankin taped plastic strips to his television screen. He used a grease pencil to trace body movement. He plugged his findings into computer spreadsheets. He's still at it today.
Recently, Mankin looked over clips of Bonds, from 1988 and the present. Conclusion?
"There's absolutely no change," said Mankin, who runs a Web site devoted to bat speed. "The only difference is that back then, most of his home runs were just enough to clear a 360-foot fence. Now, he's up to 400-some with the same dang swing."
The same dang swing. Only faster. In an excellent 2005 San Diego Union-Tribune article detailing the effects of steroid use on power hitting, major league scouts claim Bonds' bat speed not only stopped declining but also increased during the time he worked with Anderson -- an observation consistent with Adair's weight-to-bat speed formula.
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More on confidence: "Game of Shadows" reports that performance enhancers improved Bonds' eyesight, helping him track pitches. Coincidence? Not necessarily. Extra bat speed means extra time to differentiate between a fastball and a slider.
Moreover, a 2002 University of California San Francisco study found that older men with higher testosterone levels performed better on cognition tests than men with lower levels. Two years later, Harvard researchers discovered that men with higher testosterone levels are quicker to solve spatial-relationship problems.
Really, what is spotting and crushing a major league fastball if not a spatial-relationship problem ... played out at warp speed?
"People talk about bat speed, but nobody talks about [Bonds'] eyesight," said the major league scout. "He sees a pitch so quick, so early. He can see it and relay that information to his muscles faster than anyone else. That's what all good hitters do. They know what the ball is when it has been out of the pitcher's hand for just 10, 15 feet. Only special people do this."