Sit-to-Stand Power Across Adulthood in Three Latin American Countries: Sex-Specific Relative and Allometric Reference Values From a Multicenter Study.

Sit-to-stand (STS) power is a practical field-based indicator of lower-limb muscle power and functional performance across adulthood, yet reference values have been derived mainly from European cohorts, and allometric STS power remains scarcely described in Latin America. This multicenter cross-sectional study developed sex- and age-specific descriptive reference benchmarks for relative and allometric STS power in adults from Chile, Colombia, and Ecuador, and examined age- and country-related variation. A total of 1254 healthy adults aged 18-80 years performed a standardized five-repetition STS test. Relative STS power was estimated using established biomechanical equations, and allometric STS power was calculated by normalizing absolute power to height squared. Sex-specific empirical percentiles were generated across 10-year age bands, and generalized additive models were used to characterize cross-sectional age-related patterns and assess country-specific heterogeneity. Relative STS power was lower in older age groups in both sexes, with median values ranging from 4.50 to 2.40 W·kg-1 in women and from 5.20 to 2.80 W·kg-1 in men between the 18-29 and 70-80 year groups. Allometric STS power showed a similar cross-sectional pattern, with median values ranging from 114.35 to 61.30 W·m-2 in women and from 126.70 to 74.10 W·m-2 in men. Ecuador showed higher distributions of relative STS power than Chile and Colombia, and cross-sectional age-related patterns differed across countries. Exploratory physical activity gradients were attenuated after adjustment. These pooled, equation-derived percentiles are regional summary benchmarks rather than country-specific reference values and should be interpreted cautiously in younger adults and smaller strata.