Physical fitness, rather than self-reported physical activities, is more strongly associated with low back pain: evidence from a working population

Physical activity is suggested to be important for low back pain (LBP) but a major problem is the limited validity of the measurement of physical activities, which is usually based on questionnaires. Physical fitness can be viewed as a more objective measurement and our question was how physical activity based on self-reports and objective measured levels of physical fitness were associated with LBP. We analyzed cross-sectional data of 1,723 police employees. Physical activity was assessed by questionnaire (SQUASH) measuring type of activity, intensity, and time spent on these activities. Physical fitness was based on muscular dynamic endurance capacity and peak oxygen uptake (VO2 peak). Severe LBP, interfering with functioning, was defined by pain ratings a parts per thousand yen4 on a scale of 0-10. Higher levels of physical fitness, both muscular and aerobic, were associated with less LBP (OR: 0.54; 95% CI: 0.34-0.86, respectively, 0.59: 95%CI: 0.35-0.99). For self-reported physical activity, both a low and a high level of the total physical activity pattern were associated with an increase of LBP (OR: 1.52; 95%CI: 1.00-2.31, respectively, 1.60; 95%CI: 1.05-2.44). These findings suggest that physical activity of an intensity that improves physical fitness may be important in the prevention of LBP.