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Extending the time spent in moderate physical activity can reduce the risk of back pain among patients who are overweight or obese.
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AAOS Now

Published 12/1/2013
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Nicolle Heller

How Are Back Pain, Obesity, and Exercise Connected?

Study examines influence of exercise on the relationship between low back pain, obesity

Americans who are extremely obese have a four-fold increased risk of back pain, yet adding just 20 minutes of light exercise each day can lower that risk by a surprising 32 percent, according to an award-winning study presented at the North American Spine Society (NASS) 2013 annual meeting.

The study, “Does Physical Activity Influence the Relationship Between Low Back Pain and Obesity?” was recognized as the “Outstanding Paper” on medical and interventional science by The Spine Journal.

“Historically, based on anecdotal evidence and very limited studies, spine specialists have told overweight patients that losing a relatively modest amount of weight or even marginally increasing their exercise can help reduce their risk of back pain,” said Michael L. Reed, PT, DPT, OCS, MTC, NASS annual meeting program co-chair. “This large, precise study finally provides the hard data we need to back up those beliefs and really help to put weight behind our words as we make these recommendations to our patients.”

Population-based study
The researchers performed a cross-sectional U.S. population-based study of a cohort of 6,796 adults from the 2003–2004 National Health and Nutrition Examination Survey (NHANES). Lower back pain status was determined by the participant’s responses to a questionnaire. Body mass index (BMI) was calculated during a physical examination. Participants were divided into the following four groups:

  • normal weight—BMI less than 25
  • overweight—BMI of 25 to 30
  • obese—BMI of 31 to 35
  • extremely obese—BMI of 36 or higher

Summary measures of physical activity were computed based on intensity cut-offs, percentile intensities, and bout. Demographics, social history, and comorbid health conditions were used to build adjusted weighted logistic regression models using Akaike Information Criterion (AIC). Outcome measures included demographic information, an in-depth health questionnaire, physical examination details, and 7-day free-living physical activity monitoring using accelerometry.

The researchers concluded that, in the U.S. population, the risk of lower back pain increases as BMI increases. For individuals of normal weight, the risk of lower back pain was just 2.9 percent. That risk nearly doubled (to 5.2 percent) for those who were overweight. The risk of lower back pain was 7.7 percent among obese individuals, and was highest (11.6 percent) among those who were extremely obese.

The researchers also found that smoking was consistently the strongest predictor of lower back pain across the BMI spectrum.

The impact of exercise
The researchers also found that physical activity can temper these risks. In the overall model, the best physical activity predictors of low back pain were in the moderate- and high-intensity ranges, but these effects were small. When researchers looked at the BMI categories, they found that time spent in sedentary and moderate activity ranges had a more robust influence on back pain status in the overweight, obese, and extremely obese groups.

“Perhaps the best news out of this study is that people can make big gains with some incredibly modest changes in activity,” said lead author Matthew Smuck, MD, chief of physical medicine and rehabilitation and associate professor at the Stanford University School of Medicine.

For example, when the average, overweight person stops being sedentary and starts moving (including even very light activity such as folding clothes or walking slowly), he or she will remain active, on average, for 1 hour and 53 minutes. Simply extending this average by 7 minutes—to 2 hours—reduces the risk of back pain by 17 percent.

Overweight Americans who increase the amount of time they spend in moderate activity (walking briskly, water aerobics, riding a bike, ballroom dancing, and general gardening) by less than 20 minutes a day can reduce their risk of back pain by 32 percent.

Finally, noted the authors, simply pushing just a little harder during exercise is very beneficial. Although people who are extremely obese spend an average of just 1.3 minutes in moderately intensive activities, they can reduce their odds of having back pain by 38 percent simply by extending this average time at or above the moderate activity intensity range by less than one additional minute every time they exercise.

Dr. Smuck’s coauthors include Ming-Chih Kao, PhD, MD; Nikhraj Brar, MD; Agnes Martinez-Ith; Jongwoo Choi, MD; and Christy Tomkins-Lane, PhD.

Disclosure information: Dr. Smuck—ArthroCare; EMKinetics; Cytonics Corp.; International Spine Intervention Society; The Spine Journal. No information on the other authors is available.

Adapted from a press release by Nicolle Heller, media relations NASS.

Bottom Line

  • This award-winning study examined the relationship between low back pain and obesity, as well as the impact of exercise on reducing the risk of low back pain.
  • In the U.S. population, the risk of low back pain increases as body mass index (BMI) increases; the risk of low back pain among those who are extremely obese is four times greater than among people of normal weight.
  • Smoking is a predictor of low back pain, regardless of a person’s weight.
  • Researchers found that increasing the amount of time spent in moderate exercise by just 20 minutes a day can lower an overweight person’s risk of low back pain by 17 percent.