Last year, the 37-year-old agricultural sales director from Post Falls, Idaho, noticed a throbbing sensation in this thumbs whenever he typed. He switched to tapping with his index finger, then his middle digit and finally his pinky. But his thumbs pained him to the point where he can't even press the buttons on his TV remote control.
After months of aching, Claypool took a break. Now he only uses his BlackBerry to send short messages, typing with the tip of a pencil eraser whenever his thumbs get sore.
"It affects business because I can't whack away on my BlackBerry like I used to," he said. "It's just too painful."
Repetitive motion injuries, which have long afflicted desktop and laptop computer users, are invading the mobile handheld world.
There's even an informal name for the malady: "BlackBerry Thumb," a catch-all phrase that describes a repetitive stress injury of the thumb as a result of overusing small gadget keypads.
Business executives and tech-savvy consumers are increasingly using BlackBerries, Treos, Sidekicks and other devices with miniature keyboards designed for thumb-tapping to stay connected while on the go.
And that has some ergonomic and hand experts worried about injuries from overexertion.
"If you're trying to type 'War and Peace' with your thumbs, then you're going to have a problem," warned Alan Hedge, director of the Human Factors and Ergonomics Laboratory at Cornell University in Ithaca, N.Y.
No national statistics exist on how many people suffer from this type of thumb ailment, but some doctors say they are seeing an upswing in related cases, said Dr. Stuart Hirsch, an orthopedist at St. Joseph's Hospital and Medical Center in Paterson, N.J.