“…Several studies that perform a stratified by gender analysis [ 16 , 17 , 21 , 22 , 25 , 29 ] reveal gender differences on the effects of socioeconomic factors on PA. In addition, most studies find that participation in PA increases with income [ 16 , 22 , 25 , 27 , 30 ], but declines with age [ 17 , 19 , 21 , 23 , 25 , 28 , 30 , 31 ]. Generally, being married is negatively associated with PA participation [ 16 , 19 , 21 , 23 , 25 , 27 , 29 ], although some find the opposite effect [ 20 , 28 , 31 ].…”