Physiological responses and clinical associations of the one-minute sit-to-stand test and the six-minute walk test in systemic sclerosis

BACKGROUND: The One-Minute Sit-To-Stand Test (1-STST) is a simple alternative to the Six-Minute Walk Test (6MWT), but its clinical utility in systemic sclerosis (SSc) remains insufficiently characterized. This study evaluated the convergent validity of the 1-STST with the 6MWT and their associations with clinical characteristics in patients with SSc. METHODS: In this cross-sectional study, 80 adults with SSc performed both tests on the same day; 40 repeated testing after one week to assess test-retest reliability. Clinical characteristics, lung function, imaging, comorbidities, patient-reported outcomes, and physiological responses were collected. Associations were assessed using Spearman correlation analyses, and multivariable regression identified independent determinants of performance. RESULTS: The 1-STST correlated strongly with 6MWT distance (ρ = 0.78; p < 0.001) and showed good test-retest reliability (ICC 0.85). It elicited less desaturation and heart rate increase than the 6MWT. Muscular pain was more frequently reported during the 1-STST (34.2% vs. 13.8%; p < 0.005). Both tests showed moderate correlations with dyspnea and weak correlations with lung function. After excluding patients with musculoskeletal limitations, correlations between 1-STST and pulmonary function strengthened. In multivariable analyses, 1-STST performance was independently associated with age and Scleroderma HAQ, whereas 6MWT distance was associated with age and DLCO. CONCLUSIONS: The 1-STST is a valid, reliable, and pragmatic tool for assessing functional capacity in SSc. It reflects a composite functional signal influenced by musculoskeletal and cardiopulmonary factors, whereas the 6MWT more consistently reflects cardiopulmonary capacity. The 1-STST may serve as a complementary tool to the 6MWT in clinical assessment of SSc.