SATURDAY, Sept. 9 (HealthDay News) -- You can now add "BlackBerry Thumb" to the list of workplace maladies, says the American Physical Therapy Association (APTA).

BlackBerry Thumb refers to an increasingly common, repetitive-stress injury stemming from use of the popular handheld electronic devices. This stress injury causes pain and/or numbness in the thumbs and joints of the hands.

The condition is caused by spending too much time on these devices -- checking and composing e-mails, instant messaging, and accessing the Internet.

"The use of PDAs (personal digital assistants) is no longer limited to the eight hours spent in the workplace," Margot Miller, president of the APTA's Occupational Health Special Interest Group, said in a prepared statement.

"More and more, people are depending on these devices to stay in touch with friends and family before and after the work day and on the weekends, as well as having access to work when they leave the office; that is where the heart of the problem lies," Miller said.

Many PDA users are middle-aged and overuse of the handheld devices can aggravate underlying arthritis.

"Because the keyboard of the PDA is so small, and because the thumb, which is the least dexterous part of the hand, is overtaxed (for faster typing), the risk of injury just skyrockets," Miller said.

The APTA offers the following tips on how to avoid BlackBerry Thumb:

• Take frequent breaks from your PDA. Don't type for more than a few minutes at a time.
• Write fewer and shorter messages. Learn to abbreviate your responses.
• Try to avoid thumb-typing. Use your other fingers to type.
• If possible, place a support in your lap when using a PDA, so that your wrists are in a more upright position and not flexed or bent.

The APTA also recommends the following simple exercises:

• Tap each finger with the thumb of the same hand. Repeat five times.
• Alternate tapping the palm of your hand and the back of your hand against your thigh as quickly as you can. Repeat 20 times.
• Open your hands and spread your fingers as far apart as possible. Hold for 10 seconds and repeat eight times.
• Fold your hands together, and turn your palms away from your body as you extend your arms forward. You should only feel a gentle stretch. Hold for 10 seconds and repeat eight times.
• Fold your hands together, turn your palms away from your body, and extend your arms overhead. You should feel the stretch in your upper torso and shoulders to hand. Hold for 10 seconds and repeat eight times.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about repetitive motion disorders.