NEW YORK (Reuters Health) - Being physically active outside of work may protect against work-related repetitive strain injury, researchers from Canada report.

Lead researcher Charles R. Ratzlaff told Reuters Health: Leisure-time physical activity may "facilitate better balance and nutrition to the musculoskeletal system," which may counter the repetitive or sedentary effects of many jobs.

Repetitive strain injuries (RSIs) are caused by repeating the same motions over and over at work, such as typing on a keyboard or assembling products in a factory line.

Ratzlaff, from the University of British Columbia, Vancouver and colleagues analyzed the prevalence and correlates of work-related RSI by analyzing data from the 2003 Canadian Community Health Survey for 58,622 full-time workers between the ages of 15 and 74 years.

The data show, reported Ratzlaff, that "RSI is a common problem in Canada, affecting more than 1 in 10 Canadians overall. Roughly half of all RSIs are work-related -- most injuries involve the upper body, such as the wrist/hand, shoulder and elbow. RSI often strikes in the prime working years (between age 30 and 49). Women are at higher risk for work-related RSI than men.

The increasing prevalence of RSI, Ratzlaff noted, "may be related to an increase in sedentary lifestyles and occupations due to many more office, computer, and technology-based jobs."

An inactive leisure life emerged as a risk factor for work-related RSIs. "Physical activity outside of the work place (in leisure time) may reduce a person's likelihood of sustaining an upper body RSI at work, as well as provide many other health benefits," Ratzlaff said.

And contrary to what some may think, participating at moderate levels in activities that place some force on the upper body, like tennis and baseball, does not increase the risk for work-related RSI.