The minimum sit-to-stand height test: reliability, responsiveness and relationship to leg muscle strength

Objective: To determine the reliability of the minimum sit-to-stand height test, its responsiveness and its relationship to leg muscle strength among rehabilitation unit inpatients and outpatients. Design: Reliability study using two measurers and two test occasions. Secondary analysis of data from two clinical trials. Setting: Inpatient and outpatient rehabilitation services in three public hospitals. Subjects: Eighteen hospital patients and five others participated in the reliability study. Sevety-two rehabilitation unit inpatients and 80 outpatients participated in the clinical trials. Methods: The minimum sit-to-stand height test was assessed using a standard procedure. For the reliability study, a second tester repeated the minimum sit-to-stand height test on the same day. In the inpatient clinical trial the measures were repeated two weeks later. In the outpatient trial the measures were repeated five weeks later. Knee extensor muscle strength was assessed in the clinical trials using a hand-held dynamometer. Results: The reliability for the minimum sit-to-stand height test was excellent (intraclass correlation coefficient (ICC) 0.91, 95% confidence interval (CI) 0.81-0.96). The standard error of measurement was 34 mm. Responsiveness was moderate in the inpatient trial (effect size: 0.53) but small in the outpatient trial (effect size: 0.16). A small proportion (8-17%) of variability in minimum sit-to-stand height test was explained by knee extensor muscle strength. Conclusions: The minimum sit-to-stand height test has excellent reliability and moderate responsiveness in an inpatient rehabilitation setting. Responsiveness in an outpatient rehabilitation setting requires further investigation. Performance is influenced by factors other than knee extensor muscle strength.