"In every obvious way, Randy Johnson and Tim Lincecum are the polar opposites of pitching. Separated by 20 years in age, nearly a foot in height and 270 victories, they embody contrast: Johnson as the older, taller, surly left-hander; Lincecum as his younger, shorter, right-handed, more personable counterpoint.

Yet for all their differences, these San Francisco starters and Cy Young Award winners have each flung fastballs in excess of 100 miles an hour, a rarity even in the rarefied air of the major leagues.

The question, then, is how? How can Johnson, the towering lefty with the intimidating scowl, and Lincecum, the marvel of motion who has been mistaken for a batboy, accomplish the same feat in such different ways?

"It's similar to how a Corvette and a Porsche look so different and drive so fast," said Rick Peterson, the biomechanics expert and former pitching coach for the Oakland Athletics and the Mets. "Under the hood there are so many similarities."

The differences are easier to spot. Johnson, 45, rises like a smokestack from the pitching mound, and he throws with a lower, almost sidearm arm angle, longer arm action and fewer moving body parts than Lincecum.

Lincecum, 25, learned his mechanics from his father, Chris, who works at Boeing and doubles as a pitching guru. His power comes from constant and harmonious motion, from his old-fashioned windup to a Luis Tiant-like body turn, then uncoiling into an unusually long stride. Lincecum likes to say that he uses every body part from his ankles to his ears.

"Short righty and supertall lefty," the 5-foot-11 Lincecum said in Washington this month. "With our deliveries, that's about as opposite as you can get."

The similarities lie beneath the surface, rooted in biomechanics - the physics of fastballs, if you will.

A lifelong philosopher of pitching, Chris Lincecum has a frame similar to his son's and still hit 88 m.p.h. on a radar gun when he was in his 50s. In his son, as well as in the 6-10 Johnson, he sees the same creation of leverage, the same generation of power from the ground up."