Movement Variability and Accuracy Within the Temporal and Spatial Domains When Provided a Vibrotactile Stimulus

Abstract

Different means of informing body movements can include visual, auditory, and vibrotactile (VT) stimuli. Each method may guide movements within the temporal (TEMP) and spatial (SPAT) domains in varying ways. As VT stimuli has become more accessible, it is important to understand how users interpret this method of instruction to promote patterned movements. PURPOSE: Determine the effects of VT stimulus pattern speed on TEMP and SPAT movement variability (VAR) and accuracy (ACC). METHODS: Sixteen young healthy subjects were recruited. Participants completed a continuous wrist flexion and extension activity. The task involved matching wrist motion with two different VT pattern speeds (FAST, SLOW) provided via motors attached to the forearm. An electrogoniometer captured wrist movement. Five 20s trials with 2min rest periods were completed for the two speeds. Flexion/extension movements were combined for further analysis. Absolute (STDEV) and relative (CV) VAR, and ACC (mean absolute error) for TEMP and SPAT domains were calculated within individuals. 5x2 linear mixed models accounting for repeated measures compared the variables across pattern speeds and trial numbers. Post-hoc Tukey HSDs identified differences for trial effects. RESULTS: No significant interactions were found in either domain. Significant pattern speed effects were observed in the TEMP domain for VAR (STDEV: FAST 0.07s, SLOW 0.13s, p < .05; CV: FAST 12.9%, SLOW 16.8%, p < .05), and ACC (FAST 0.05s, SLOW 0.10s, p < .05). VAR in the both domains and TEMP ACC changed significantly over the 5 trials (all, p < .05; ACC SPAT, p > .05). Post-hoc tests revealed trial 1 to be different from all subsequent trials for TEMP and SPAT VAR (STDEV TEMP: #1: 0.15s, #5: 0.08s, p < .05; STDEV SPAT: #1: 7.7deg, #5: 4.7deg, p < .05; CV TEMP: #1: 20.8%, #5: 13.2%, p < .05; CV SPAT: #1: 11.9%, #5: 5.9%, p < .05), and ACC TEMP (#1: 0.11s, #5: 0.07s, p < .05). CONCLUSIONS: VT stimulus appears capable of producing a desired continuous wrist movement at multiple pattern speeds. TEMP VAR was lower and TEMP ACC was higher for the FAST speed, while SPAT measures did not differ between speeds. Lower TEMP and SPAT VAR, and higher TEMP ACC were observed by trial 2, with improved performance maintained in the remaining trials. A lack of change in SPAT ACC may reflect limited SPAT guidance provided to subjects.