Physical activity fails to show link with chronic musculoskeletal pain

By Lucy Piper, Senior medwireNews Reporter

Neither little nor excessive physical activity contributes to chronic musculoskeletal pain (CMP) in people who are middle-aged or older, Japanese study findings suggest.

“[O]ur cross-sectional investigation did not detect any significant linear or quadratic associations of PA [physical activity] and CLBP [chronic low back pain] or CKP [chronic knee pain]”, the study researchers report in the Journal of Epidemiology

This null finding contradicts previous research suggesting non-linear or U-shaped relationships between PA and CMP and is at odds with PA being recommended as an intervention for the latter.

But the researchers, led by Masamitsu Kamada (National Institute of Health and Nutrition, Tokyo, Japan), say that the “potential benefits of PA on CMP still deserve discussion.”

They suggest that possible ways in which PA could reduce the risk of CMP include by decreasing mechanical stress, improving blood flow to painful areas, relieving psychological stress and increasing pain tolerance.

For the study, 4559 rural community-dwelling adults aged 40 to 79 years from Shimane in Japan completed a survey assessing their sociodemographic and health status, as well as the International Physical Activity Questionnaire and a modified version of the Knee Pain Screening Tool.

CLBP and CKP were prevalent, affecting 14.1% and 10.7% of participants, respectively.

The 55% of people who engaged in the recommended level of moderate-to-vigorous PA (≥8.25 MET-hours/week) were no more or less likely to have CLBP or CKP than the 25.6% who did not engage in moderate-to-vigorous PA.

Similarly, after taking into account confounding factors, such as self-rated health, depressive symptoms, smoking and chronic disease, the prevalence ratios for CKP and CLBP were a nonsignificant 1.12 and 0.93 for individuals with the lowest levels of PA and 1.26 and 1.10 for those with the highest levels.

There was also no indication that PA was associated with CMP through an interaction with body mass index (BMI) or prior injury, which were both significantly associated with CMP. And the prevalence ratios were further attenuated toward the null when the researchers adjusted for medication use and consultation with physicians.

“As seeking medications and undergoing outpatient treatment is directly associated with not only pain but also PA, these results are plausible”, say the researchers.

“Our findings thus emphasize that future research on the relationship between PA and CMP should consider effects of BMI, injury, and pain management factors.”

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