Supplementary Material for: Test-retest reliability of movement displacement during a 20-sec stepping-in-place test in community-dwelling older adults with and without supportive care

Introduction: Our recent reports have shown that movement pattern and displacement assessed with an infrared depth sensor during a 20-sec stepping in-place test (ST) correaltes with measures of balance and need for assistance in older individuals. This study investigated ST test-retest reliability in community-dwelling older adults with and without supportive care. Methods: Two groups were included: those not participating (HO: n= 25, 74.7 ± 5.2 yr) and those participating (DSU: n= 41, 78.8 ± 5.8 yr) in regular senior day services (supportive care). HO completed three ST trials, separated by 1 week, while DSU completed two ST trials during the same half-day supportive care visit. Testing was conducted with eyes open. ST measures included head movement path distance [TMD], maximum movement displacement [MMD], knee movement pathlength [KMD], and stepping rate (STEP). TMD•KMD-1 ratio indicated upper-body sway relative to lower-body. Test-retest reliability (Intra-class correlation coefficients; ICC) and between-trial and between group differences (ANCOVA, adjusting for age) were assessed. Results: After adjusting for age, TMD, KMD, TMD•KMD-1 were lesser and STEP was greater in HO than DUS. HO ST variables did not differ across testing days. HO ICC (1, 3) for TMD (0.911 (95% confidence interval: 0.827-0.958)), MMD (0.918 (0.814-0.961)), KMD (0.838 (0.685-0.923)), and TMD•KMD-1 (0.940 (0.884-0.872)) showed strong to very strong reliability. Similaraly, DSU ST variables did not differ across same day trials and ICC (1, 2) for TMD, KMD, and TMD•KMD-1 displayed very strong reliability. Conclusion: These ST variables exhibited excellent test-retest reliability of discriminating between community-dwelling older adults with and without supportive care.