The role of sexual intercourse in the etiology of carpal tunnel syndrome. "The etiology of non-occupational carpal tunnel syndrome is not well understood. It is proposed that carpal tunnel syndrome can develop during sexual intercourse when the hands become repeatedly extended while under pressure from the weight of the upper body. Of the eight risk factors associated with non-occupational carpal tunnel syndrome, age, marital status, pregnancy and use of hormonal agents can be explained by changes in the frequency of sexual intercourse. On the other hand, obesity, macromastia and large chest circumference can be explained by the increased pressure imposed on the wrists by the heavier upper body associated with such conditions. The bilaterality of carpal tunnel syndrome can be explained by the fact that both hands are needed to support the upper body during sexual intercourse. A parallel decrease in the frequency of sexual intercourse and the incidence of carpal tunnel syndrome between the sixth and the seventh decades of life suggests a possible cause and effect relationship between sexual intercourse and carpal tunnel syndrome."