Occupational physical activity is related to physical fitness in young workers

We evaluated the association between occupational physical activity and fitness in young workers, taking into account leisure-time physical activity, body size, and smoking. The study population comprised 2188 men and 1987 women, members of the Northern Finland birth cohort 1966, who participated in the 1997-1998 follow-up survey and were employed at the time of the survey. Cardiorespiratory fitness was measured by a 4-min step test and muscular fitness by tests of maximal isometric handgrip and isometric trunk extension. Information on occupational and leisure-time physical activity and smoking was obtained by questionnaire, and body height and weight were measured during medical examination. The data were analyzed by analysis of variance and Cox regression. Men doing heavy physical work scored better in cardiorespiratory fitness, handgrip strength, and trunk muscle endurance than men doing lighter work; the finding for cardiorespiratory fitness was similar in women. The associations were independent of leisure-time physical activity, body weight and height, and smoking. A positive association was found between heavy physical work and a high level of fitness in young workers. Due to limitations of the study setting, causality cannot be asserted, but a training effect of heavy work would not seem unreasonable. Previous studies have suggested a reversal of the positive effect of heavy work on fitness with advancing age. Therefore, regular monitoring of workers' fitness at an early phase is justified to enable assessment of workers' capacity for heavy jobs and any possible need for fitness-improving activities.