William Whitson is a 21st century digital cowboy.

Instead of a six-shooter, he wears an electronic gizmo in a plastic holster on his belt. Instead of an index finger, he relies on a thumb. Both thumbs, actually.

Whitman, an assistant city manager in Port Orange, Fla., packs a wireless communicator that relies on thumb typing for composing e-mail.

"I can whip out a full-page memo pretty quick," says Whitson, who at first dreaded learning how to use the RIM BlackBerry. But he quickly developed a knack for using only his thumbs to compose and reply to electronic messages. Now he can't imagine getting through a busy day of meetings without his thumb-guided gadget.

"All thumbs" is no longer a synonym for "klutzy" but rather a necessary skill for using the tiny keyboards that help people communicate through cell phones and personal digital assistants.

As users peck out text messages and e-mails, they use the edges of their thumbs instead of their fingertips to strike keys the size of baby aspirin. Many who rely on "texting," or thumb-typing short messages, make every letter count. Example: "How r u?"

Sales representative Ted Bevalacqua uses his cell phone to send wireless messages to clients -- and to stay in touch with girlfriend Elizabeth Garcia. Using his thumbs, he types, "Thanks for making me smile." She replies with "Xo xo," meaning hugs and kisses.

RIM's BlackBerry launched the thumb revolution for e-mail and short messages when it was introduced three years ago, wireless industry analysts say. The keys on standard computer keyboards are square, but the BlackBerry's designers made the keys oval, a thumb-friendly shape that allowed for speed and typing comfort.

Before the BlackBerry and its tiny keyboard, users of handheld gadgets relied on handwriting recognition. These systems, with trade names such as Graffiti and Jot, required owners to use a stylus to enter text using a slightly modified alphabet that was easy for the computer to translate.

Many users who never became proficient enough with the stylus were quick to embrace typing with the edges of the thumb. In recent months, vendors have created add-on thumb boards for both Palm and Microsoft Windows Pocket PC devices.

Industry studies attest to the new power of the thumb. Text messaging has increased nearly 500 percent in the past year, says Lisa Jo Wilson-Knight, executive vice president of marketing for AT&T;'s mobile multimedia services.

"I think we're just on the cusp of greater growth," she says. "Text messaging has been very popular in Europe for several years, and there's a generation of thumb users in Japan."

Because many users rely on text messaging to help plan their social lives, it makes sense that people at the center of a social circle help spread thumb technology by demonstrating good technique to friends, says Wilson-Knight.

The primacy of the thumb comes as no surprise. After all, it gives humans the ability to grasp objects and separates us from other members of the animal kingdom.

The thumb seems surprisingly resistant to the pain brought on by repetitive use of keyboards, mice and other input devices. Dr. Jeff Darin, a hand surgeon at the Jewett Orthopedic Center in Orlando, Fla., says he has seen no patients with thumb injuries related to small keyboards. In contrast, a large number of his patients are individuals with injuries related to using a full-size keyboard and mouse.

"The thumb is the most mobile joint [on the hand] and can tolerate the most stress," he says.

But there's no telling whether thumbsters will develop injuries over time.

"The use of thumb keyboards only hit the big time recently," says Dr. Jerome McAndrews, national spoksman for the American Chiropractic Association in Arlington, Va. "We haven't seen injuries yet. It's too early to tell what impact there might be from sustained use of these devices.

"Besides, many individuals with PDAs have been typing on standard keyboards for years, so it will be difficult to determine the exact cause of pain or injuries."

A veteran BlackBerry user and observer of the PDA field agrees that thumb typing isn't physically painful -- just painfully slow.

When he receives an e-mail on his RIM BlackBerry, Tim Bajarin generally limits his responses to a simple yes, no or maybe.

"For me, typing more than a few words is difficult and time-consuming -- although in fairness, I know of people who can type about 35 words per minute with their thumbs," says Bajarin, president of Creative Strategies, a San Francisco Bay area marketing research firm.

Alternatives to thumb input include laptop computers and another class of keyboards made for PDAs that fold up like an accordion, yet spread out to the size of a standard keyboard.

Bajarin says he would like to see some form of folding keyboard incorporated into a cell phone or PDA.

Another improvement would be enabling keyboards to control the PDA, says Ed Suwanjindar, product manager of the Microsoft Mobility Group. Today's add-on keyboards are limited to typing, so users need a stylus to issue commands and select other programs, "and that's awkward," he says.

Chris Cobbs writes for the Orlando Sentinel, a Tribune Publishing newspaper.