Abstract

Objective: To describe age-related differences in Sit-to-Stand Test (STST) performance (5 repetitions, 30 s, and 1 min) and their association with PA levels. Design: We estimated age-related trajectories for 3 STST across physical activity (PA) strata defined by self-reported IPAQ-SF (low, moderate, high) and quantified the PA effects. In a multicenter cross-sectional study from 12 cities in three BLINDED countries (n=1283; 56% women; 18 to 80 y), performance was assessed with 5rep-STST (seconds), 30s-STST (repetitions), and 1min-STST (repetitions). Primary analyses used generalized additive models with a common age spline, adjusted for sex, BMI, and smoking; multiplicity-adjusted pairwise contrasts were computed. An age-equivalent advantage (high vs. low PA) was derived using a parametric bootstrap; distribution-aware models were tested for robustness. STST performance declined nonlinearly with age. Results: Higher PA was associated with better performance in repetition-based tests; 5rep-STST effects were small. In 1min-STST, high exceeded low by similar to 2.5 repetitions, yielding an age-equivalent advantage of similar to 5 to 7 years; for 30s-STST, advantages were similar to 3 to 5 years. Sensitivity analyses corroborated these findings. Conclusions: In this Latin American cohort, STST performance declined nonlinearly with age but was consistently better in those with higher habitual PA, regardless of sex, BMI, or smoking.