Measuring quadriceps strength in adults with severe or moderate intellectual and visual disabilities: feasibility and reliability

Background: A feasible and reliable instrument to measure strength in persons with severe intellectual and visual disabilities (SIVD) is lacking. The aim of our study was to determine feasibility, learning period and reliability of three strength tests.
Methods: Twenty-nine participants with SIVD performed the Minimum Sit-to-Stand Height test (MSST), the Leg Extension test (LE) and the 30 seconds Chair-Stand test (30sCS), once per week for 5 weeks. Feasibility was determined by the percentage of successful measurements; learning effect by using paired t test between two consecutive measurements; test–retest reliability by intraclass correlation coefficient and Limits of Agreement and, correlations by Pearson correlations.
Results: A sufficient feasibility and learning period of the tests was shown. The methods had sufficient test–retest reliability and moderate-to-sufficient correlations.
Conclusion: The MSST, the LE, and the 30sCS are feasible tests for measuring muscle strength in persons with SIVD, having sufficient test re-test reliability.