Study highlights role of physical activity in the relationship of BMI, low back pain

NEW ORLEANS — A study presented at the North American Spine Society Annual Meeting indicated that small increases in moderate physical activity can reduce the risk of back pain in Americans with higher body mass indices.

“We demonstrated that modest reductions in sedentary time and increases in moderate physical activity have a greater impact on low back pain risk in overweight Americans than on the general population,” Matthew Smuck, MD, said during his presentation.

The research won The Spine Journal Outstanding Paper Award for Medical and Interventional Science.


Matthew Smuck

To confirm and quantify the relationship between body mass index and low back pain (LBP) and to describe the role of physical activity in this relationship, Smuck and colleagues used the NHANES database to identify nearly 6,800 subjects. The investigators analyzed subjects’ self reports of low back pain, body mass index (BMI) determined by physical examination and physical activity, which was determined by accelerometry or a continuous activity monitor for 7 days.

The investigators found a step-wise increase in LBP risk with increased BMI, and Smuck noted “a four-fold overall increased risk from normal weight to morbidly obese.”

Looking at overall BMI, the researchers initially discovered weak associations between activity and the odds ratios for LBP with the greatest predictors being vigorous and moderate activity levels. However, when they stratified their findings by BMI, the investigators found moderate sustained activity and sedentary activity were stronger predictors of back pain status.

They discovered that for each population standard deviation increase in the number of minutes in sustained, nonsedentary activity, the odds of having low back pain in overweight subjects decreased by 17%.

“To put that in other terms, the mean sustained, nonsedentary activity time in this cohort was 114 minutes. [By] increasing that by just 7 minutes, they reduce their back pain risk by 17%,” Smuck said.

In that same group, increasing moderate activity by less than 20 minutes a day reduced the risk of LBP by 32%. The researchers found similar results for morbidly obese subjects.

Smuck cited the use of a pre-existing dataset and inability to stratify back pain severity among the weaknesses of the study.


Smuck M. Does physical activity influence the relationship between low back pain and obesity? Presented at: North American Spine Society Annual Meeting; Oct. 9-12; New Orleans.

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