Reliability Of The Gallon Jug Shelf Transfer Test: An Object Transfer Test For Older Individuals

Abstract

The declines in power during the performance of daily activities are associated with a reduced ability to perform basic and instrumented activities of daily living. The Gallon Jug Shelf Transfer Test (GJST) is a validated upper body muscle function test that can be used to quantify power and monitor functional changes in older persons. PURPOSE: Although the validity of the GJST and its predictive equations for transfer power has been established, the reliabilities of the GJST power equations need to be assessed if they are to be used in clinical or research environments. Therefore, this study aims to evaluate the intra-rater and test-retest reliabilities of the GJST. METHODS: 40 independently-living seniors between the ages of 50-90 performed two sets of 3 repetitions of the GJST separated by 48 hours on Day 1 and the same pattern of testing on Day 2. Using the predictive equations developed in our laboratory, the values for peak power (PP) and average power (AP) were then computed. Statistical analyses to assess various forms of reliability included calculating intraclass correlation coefficient (ICC), confidence intervals (CI), coefficient of variation (CV), standard error of measurement (SEM), and minimal detectable change (MDC) values. Further Bland-Altman plots evaluate the agreement among the tests. RESULTS: Intraclass correlation coefficients (ICC > .90, p < .0001), Cronbach’s alpha, and Bland-Altman analyses of between-trial and between-day test-retest reliability for peak and average power indicated excellent reliability. Cronbach’s α and ICC for trial 2 (days 1 & 2) and day 2 (trials 1 & 2) slightly increased, compared to trial 1 (days 1 & 2), and day 1 (trials 1 & 2). The lines of equality for all Bland-Altman plots, whether showing between-day or between-trial comparisons, fell within the LOA showing that there was no significance for the difference scores (p < .05). Bias, SD, LOA, CV, SEM, and MDC, slightly decreased for trial 2 (days 1 & 2) and day 2 (trials 1 & 2) compared to trial 1 (days 1 & 2), and day 1 (trials 1 & 2) for peak and average power. CONCLUSIONS: Based on our statistical analyses, the GJST has proven to be a safe, easy to administer, ADL- specific, and highly reliable assessment for determining upper body power for healthy older adults.