Long-Term Resistance Training and Risk of Type 2 Diabetes.

Importance: The optimal long-term patterns of resistance training, including volume, consistency, and integration with other lifestyle behaviors, remain unclear. Objective: To examine the association of long-term resistance training with risk of incident type 2 diabetes (T2D) and to assess joint associations with aerobic physical activity and sedentary behavior. Design, Setting, and Participants: This prospective cohort study assessed the data from 3 ongoing US studies: the Nurses' Health Study (June 30, 2002, to June 30, 2021), the Nurses' Health Study II (June 30, 2003, to June 30, 2021), and the Health Professionals Follow-up Study (June 30, 1992, to June 30, 2021). Follow-up was completed June 30, 2021. Participants included adult health care professionals who had undergone at least 3 assessments of resistance training between 40 and 60 years of age for trajectory analysis. Data were analyzed from April 30 to September 30, 2025. Exposure: Time spent in resistance training was assessed every 2 to 4 years and categorized into 5 groups: consistently low, high to low, low to high, fluctuating, and consistently high. Long-term resistance training was characterized using cumulative means and trajectory patterns between ages 40 and 60 years in the Nurses' Health Study II. Main Outcomes and Measures: The main outcome was incident T2D. Multivariable-adjusted hazard ratios (HRs) and 95% CIs were estimated using Cox proportional hazards regression models with time-varying resistance training. Results: Among 143 715 adults included in the analysis (mean [SD] age, 56.0 [10.5] years; 78.3% women), 10 038 incident T2D cases occurred during a mean (SD) follow-up of 19.2 (5.0) years. Compared with no resistance training, engaging in 2 or more hours per week of resistance training was associated with a lower T2D risk (HR, 0.73; 95% CI, 0.66-0.81). In trajectory analyses, participants with consistently high levels of resistance training (≥0.5 h/wk across midlife) had a 42% lower T2D risk (HR, 0.58; 95% CI, 0.45-0.74), and a low to high pattern was associated with a 21% lower risk (HR, 0.79; 95% CI, 0.66-0.94), compared with consistently low levels of resistance training. Participants who met recommendations for both aerobic activity (≥15 total metabolic equivalent h/wk) and resistance training (≥1 h/wk) and limited television viewing (<2 h/d) had the lowest T2D risk (HR, 0.38; 95% CI, 0.34-0.42) compared with those meeting none of the recommendations. Conclusions and Relevance: In this prospective cohort study, resistance training among US adult health care professionals was associated with substantially lower T2D risk, particularly when performed consistently over midlife and combined with adequate aerobic activity and limited sedentary television viewing. These findings support the inclusion of resistance training as a key component of lifestyle recommendations for diabetes prevention.