Tendons in the hand can thicken abnormally and develop tendinitis in people who text frequently using their thumbs, says a study published online in the American Journal of Physical Medicine & Rehabilitation.
Even when texting with two thumbs, most people tend to put greater stress on the thumb of their dominant hand, the study found. Repetitive joint movements are a common cause of chronic tendon injuries in large joints, such as the shoulder, but overuse injuries of the small tendons have received little attention, it said.
Researchers in Turkey recruited 149 people, ranging from 18 to 40 years old, for the study. About half the participants were ranked as frequent texters and they used a texting style that involved repeatedly flexing the joint closest to the tip of the thumb, called the interphalangeal joint. The rest sent relatively fewer texts, and also used the thumbs.
Ultrasound imaging measured the thickness of the tendon that travels through the carpal tunnel to the tip of the thumb. The researchers found this tendon was significantly larger on the dominant texting side of participants who texted frequently. Tendon thickness was associated with the number of text messages sent per day: The greater the number of texts, the thicker the tendon.
Frequent texters also reported greater thumb pain in the dominant texting hand than infrequent texters. Frequent texters sent an average of 1,209 text messages a month compared with 50 by infrequent texters.