In the study, a total of 30,074 workers were asked to provide information on their jobs, including time spent on repeated strenuous physical activities (RSPA) and time spent on repeated bending, twisting or reaching (RBTR) on a typical job. The participating workers were asked to report the cause of back pain, which was defined as experiencing pain every day for a week or more during the past year. Researchers found that the prevalence of the discomfort increased as the number of working hours spent on RSPA and RBTR activities increased.

Other unmeasured factors were also said to play a part, the scientists who analyzed the data found. Of occupations studied, carpenters had the highest prevalence among men, and nursing aides and other healthcare workers had the highest rates among women.