Association between self-reported resistance-exercise frequency and abdominal adiposity among Chinese adults: a cross-sectional study

Background Resistance exercise is included in adult physical activity recommendations, but the weekly frequency associated with abdominal adiposity in free-living adults remains unknown. We examined the association between self-reported weekly resistance-exercise frequency and abdominal adiposity; an exploratory secondary analysis compared ≥3 days/week with 2 days/week. Methods This single-center cross-sectional study analyzed 913 Chinese adults selected from the 3,411 adults consecutively screened at the Health Examination Center of Taizhou People’s Hospital Affiliated to Nanjing Medical University between November 2025 and July 2026. Self-reported resistance exercise was grouped as 0, 1, 2, or ≥3 days/week. Body roundness index (BRI) was the primary outcome, with waist circumference, body mass index (BMI), and waist-to-height ratio (WHtR) as the secondary outcomes. Multivariable linear regression analyses with heteroskedasticity-robust standard errors were adjusted for age, sex, aerobic moderate-to-vigorous physical activity (MVPA), sedentary time, smoking history, and alcohol consumption. The primary analysis used complete cases; multiple imputation was used to evaluate robustness in the 2,958 participants remaining after clinical exclusions, alongside additional sensitivity analyses. Results Of the 913 participants, 613 (67.14%) reported no weekly resistance exercise, 90 (9.86%) reported 1 day/week, 96 (10.51%) reported 2 days/week, and 114 (12.49%) reported ≥3 days/week. In the fully adjusted model, BRI was lower among participants reporting 2 days/week (β, −0.24; 95% CI, −0.46 to −0.03; p = 0.03) and ≥3 days/week (β, −0.39; 95% CI, −0.58 to −0.20; p < 0.01) than among those reporting 0 days/week; the association for 1 day/week was not statistically significant ( p = 0.16). The exploratory comparison of ≥3 versus 2 days/week yielded an estimated difference of −0.15 BRI units (95% CI, −0.40 to 0.11; p = 0.26). Waist circumference and the WHtR showed similar patterns, whereas the association with BMI was weaker. Multiple-imputation estimates remained inverse, while estimates in the smaller extended-covariate subset were attenuated and imprecise. Conclusion In this cross-sectional sample, self-reported resistance exercise on 2 and ≥3 days/week was associated with lower BRI and waist-based anthropometric measures than 0 days/week. The complete-case estimate comparing ≥3 with 2 days/week was imprecise, and sensitivity analyses yielded variable estimates. The substantially higher reported aerobic activity among participants reporting more frequent resistance exercise may limit the extent to which the observed association can be attributed to resistance exercise alone. These data do not establish a causal or frequency-specific effect, an optimal resistance-exercise frequency, or an additional benefit of exercising more than 2 days/week.