Using the Active Movement Extent Discrimination Apparatus to Test Individual Proprioception Acuity: Implications for Test Design

The Active Movement Extent Discrimination Apparatus (AMEDA) has been used for measuring proprioception at various joints in the body for more than two decades. The utility of this instrument for discriminating groups has been reported in terms of an area under the curve (AUC) derived from an absolute identification test. This metric has supported statistically significant group differences, but it is not clear whether the AMEDA’s testing protocol is suitable for measuring individual proprioception acuity changes. This study aimed to test the reliability, variance and absolute AUC scores obtained with the AMEDA with reference to other studies that have tested absolute identification acuity in other domains and the theoretical underpinnings of the testing protocol. We re-analyzed raw data from a 2013 study involving 65 people, most of whom were tested three times over two separate sessions on the ankle AMEDA by now assessing the accuracy of individual responses and calculating the sensitivity index, d’, in addition to the AUC. To assess reliability, we calculated the intraclass correlation coefficient (ICC) and standard error of measurement (SEM) for those who completed all three tests. Fewer than 50% of presented stimuli were accurately identified and relatively poor discrimination was achieved between adjacent stimuli (in only one case was the median d’ value greater than 1). The ICC of AUC scores across the three tests was poor (0.47). The SEM was 0.04, while 90% of participants’ AUC scores fell between 0.59 and 0.76. The variation in performance at the individual level was substantial, producing a large SEM relative to the population spread of scores. We considered potential theoretical factors that may be affecting these results and concluded that an alternative approach will be needed in order for the apparatus to be used to explore individual proprioceptive performance.