Electromyographic latency of postural evoked responses from the leg muscles during EquiTest Computerised Dynamic Posturography: Reference data on healthy subjects

Abstract

No normative data are available for the latencies of the EMG signals from the ankle muscles in response to sudden sagittal tilt (toes-UP or toes-DOWN) or shift (shift-FOR or shift-BACK) of the support surface during standing. In this study the postural evoked response (PER) paradigm on the EquiTest™ force platform was applied to 31 healthy adults (18 women and 13 men; mean age 29years). The EMG latencies (PEREMG) were computed both through the standard manual procedure and through a specially designed automated algorithm. The manually computed PEREMG onset yielded a 95% tolerance interval between 82ms and 148ms after toes-UP perturbation, between 93ms and 182ms after toes-DOWN perturbation, between 67ms and 107ms after shift-BACK perturbation, and between 73ms and 113ms after shift-FOR perturbation. When comparing the two methods, paired t-tests showed no significant mean difference (Bonferroni-adjusted p-values ranged from 0.440 to 1.000) and all Bland–Altman plots included zero difference within the limits of agreement. Therefore, the manual and the automated methods appear to be sufficiently consistent. These results foster the clinical application of PEREMG testing on the EquiTest platform.