Resistance training and total and site-specific cancer risk: a prospective cohort study of 33,787 US men

Background: Muscle-strengthening activities have been recommended for health benefits. However, it is unclear whether resistance training is associated with cancer risk, independent of total physical activity. Methods: A prospective cohort study followed 33,787 men from the Health Professionals Follow-up Study (1992–2014). Cumulative average of resistance training (hours/week) was assessed through biennial questionnaires up to 2 years before cancer diagnosis. Cox regression model was used to estimate the hazard ratio (HR) and 95% confidence intervals (CI). Results: During 521,221 person-years of follow-up, we documented 5,158 cancer cases. Resistance training was not associated with total cancer risk (HR per 1-h/week increase: 1.01; 95% CI 0.97, 1.05). We found an inverse association between resistance training and bladder cancer (HR per 1-h/week increase: 0.80; 95% CI 0.66, 0.96) and kidney cancer (HR per 1-h/week increase 0.77; 95% CI 0.58, 1.03; P_trend = 0.06), but the association was marginal for the latter after adjustment for confounders and total physical activity. Compared to participants engaging in aerobic activities only, combined resistance training and aerobic activities showed stronger inverse associations with kidney cancer risk. Conclusions: Resistance training was associated with lower risk of bladder and kidney cancers. Future studies are warranted to confirm our findings.