Association between the 30-s chair stand test and peak oxygen uptake in patients undergoing cardiopulmonary exercise testing: A large retrospective internal and external validation study

Background Peak oxygen uptake (peak VO 2 ) assessed by cardiopulmonary exercise testing (CPET) is the gold standard for evaluating exercise capacity, but its routine use is limited in many clinical settings. This retrospective study investigated the association between 30-s chair stand test (CS-30) performance and peak VO 2 and developed a prediction model with internal (Facility A) and external (Facility B) validation. Methods This study initially included 3652 patients who underwent CPET and physical function assessments between January 2020 and December 2025. After excluding 75 patients with a respiratory exchange ratio ≤ 1.04, 3577 patients were included in the analysis. A multivariable linear regression model including CS-30 performance, age, sex, and body mass index was developed using Facility A data and externally validated using Facility B data. Results CS-30 performance was independently associated with peak VO 2 after multivariable adjustment. In the external validation cohort, predicted peak VO 2 showed a moderate correlation with observed peak VO 2 ( r = 0.654, p < 0.001), with a root mean square error of 4.73 mL/kg/min and a mean bias of −2.23 mL/kg/min. Conclusions CS-30 performance was independently associated with peak VO 2 . Although the prediction model showed moderate performance in the external validation cohort, CS-30 may serve as a simple complementary functional assessment associated with exercise capacity in clinical settings where CPET is not readily available.