Muscle strength in adolescent men and future musculoskeletal pain: a cohort study with 17 years of follow-up.

OBJECTIVES: Musculoskeletal pain is highly prevalent throughout adulthood with a major impact on health, function and participation in the society. Still, the association between muscle strength and development of musculoskeletal pain is unclear. We aimed to study whether overall muscle strength in adolescent men is inversely associated with self-reported musculoskeletal pain in adulthood. DESIGN: Cohort study with baseline data from the Swedish Conscription Register and outcome information from the random population-based Swedish Living Conditions Surveys. SETTING: Sweden, 1970-2005. PARTICIPANTS: 5489 men who at age 17-19 years tested their isometric muscle strength (hand grip, arm flexion and knee extension) during the compulsory conscription. OUTCOME MEASURES: The men were surveyed regarding self-reported musculoskeletal pain; mean follow-up time of 17 (range 1-35) years. Our primary outcome was a self-report of musculoskeletal pain, and secondary outcomes were a report of 'severe pain', 'pain in back/hips', 'pain in neck/shoulders' or 'pain in arms/legs', respectively. We categorised muscle strength into three groups: low, average and high, using the 25th-75th percentile to define the reference category (average). We estimated relative risks using log binomial regression with adjustment for smoking, body mass index, education and physical activity. RESULTS: In the adjusted model, men with low overall muscle strength had decreased risk of self-reported musculoskeletal pain (0.93, 95% CI 0.87 to 0.99). We observed no such association in men with high strength (0.99, 0.93 to 1.05). Furthermore, no statistically significant increase or decrease in risk was observed for any of the secondary outcomes. CONCLUSIONS: In men, low overall isometric muscle strength in youth was not associated with an increased risk of future musculoskeletal pain. Contrarily, we observed a slightly decreased risk of self-reported musculoskeletal pain in adulthood. Our results do not support a model in which low muscle strength is a risk factor for future musculoskeletal pain.