Employees who exercise to manage high job stress may actually have reduced levels of work productivity, suggests a study in the October Journal of Occupational and Environmental Medicine, official publication of the American College of Occupational and Environmental Medicine (ACOEM).

Led by Jeffrey J. VanWormer, PhD, of Marshfield Clinic Research Foundation, Marshfield, Wis., the researchers analyzed the relationship between stress levels, physical activity, and productivity in a sample of 2,823 Minnesota workers. In general, higher stress levels were linked to greater productivity loss. Workers with higher body mass index were less productive, regardless of other factors.

After adjustment for body mass index, there was a significant interaction between physical activity and stress level. For highly stressed workers, a high level of physical activity was linked to significant productivity loss. In contrast, for workers with relatively low stress levels, physical activity had less effect on productivity.

For example, for overweight employees who exercised seven hours per week, estimated productivity loss was 11 percent for workers who were highly stressed, compared to two percent for those with lower stress levels.

Worksite wellness programs that improve employee health generally lead to increased productivity. The study provides new insights into how stress affects productivity, particularly in combination with exercise and other lifestyle factors.

The results suggest that, when stress levels are high, increased physical activity is linked to decreased productivity. The researchers write, "This may indicate that some individuals essentially cope with high levels of stress by exercising more and working less."

Stress management is "at least as economically relevant" to promoting worker health and productivity, compared to more traditional lifestyle factors, Dr. VanWormer and colleagues add. They call for more research to identify the best approaches to reducing stress in the workplace.