## 3 Results
### CNV Characteristics under Different Movement Conditions  
The grand-average CNV for each condition is shown in Figure 2. For PN latency (Table 1), there was a significant main effect of 'cue' (\(p\) = 0.002). Post-hoc tests revealed that PN latency during sit-to-stand was significantly later with the audio-visual cue compared with the visual cue (\(p\) = 0.027). This is illustrated in Figure 3. PN latency during ankle dorsiflexion was also later with the audio-visual cue compared with the visual cue, but this was not statistically significant (\(p\) = 0.067). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Movement Condition** & \multicolumn{2}{c}{**Group Mean (SD)**} & \multicolumn{2}{c}{**Post-Hoc Tests**} & \multicolumn{1}{c}{**Estimated Difference**} \\  & **ms** & & **Mean (95\% CI)** \\ \hline DF\({}_{\text{visual}}\) & 128 (226) & & \\ DF\({}_{\text{audovisual}}\) & 271 (214) & DF\({}_{\text{audovisual}}\) & 143 (\(-\)8, 294) \\ DF\({}_{\text{auditory}}\) & 205 (336) & & \\ STS\({}_{\text{visual}}\) & 168 (244) & & \\ STS\({}_{\text{audovisual}}\) & 334 (223) & STS\({}_{\text{audovisual}}\) & 166 (15, 317) * \\ \hline \hline \end{tabular}  
* \(p\) < 0.05. Group mean = mean of the mean PN latency from each participant’s averaged CNV.  
\end{table} 
Table 1: Descriptive statistics and pairwise comparisons for PN latency. Figure 3: Box and whisker plots showing comparison of CNV PN latency with visual versus audio-visual cues during ankle dorsiflexion (DF) and sit-to-stand (STS) movements. Individual datapoints are linked with light grey lines. * represents statistically significant differences (\(p\) < 0.05). to be vital to the efficacy of the intervention [21]. In the ePAS intervention, peripheral electrical stimulation is delivered just prior to the PN in order to generate an afferent volley that arrives in the motor cortex to coincide with the PN; this pairing of afferent stimulation with endogenous motor activation increases corticomotor plasticity [21] and voluntary neuromuscular activation [18]. Changes in the timing of the PN may alter the efficacy of the intervention [21; 22] and researchers should be aware that the PN latency could be altered when movement preparation is guided by a more complex cue or when additional sensory stimuli are present. It is noted that the audio-visual cue altered PN latency during sit-to-stand, but not ankle dorsiflexion (\(p=0.067\)). As shown in Figure 3, there was more variability in PN latency across the sample in the ankle dorsiflexion condition, which may have influenced the lack of significant findings for PN latency in this task. This may relate to participants being more distractable during this very simple task, as effort level is known to alter CNV characteristics [37]. The audio-visual cue did not alter the amplitude of the CNV. Therefore, regardless of the delay in motor planning described above for sit-to-stand tasks, the magnitude of cortical activation appeared unaffected. Previous studies have shown that increased complexity of the cue and movement sequence [36], or the addition of a secondary movement task [38], reduces the CNV amplitude. Thus, it is promising that the audio-visual cue in the present study was not complex enough to reduce the magnitude of neural activation for the target movement. However, it may also be important to consider the effect of the audio-visual cue when performing different types of movements or tasks. For example, it may have a different effect on upper-limb movements compared to lower-limb movements, or on complex tasks requiring increased attention compared to simple tasks. Moreover, it should be emphasized that our study was limited to healthy adults, and that the effect of different movement cues on the CNV may be different in the stroke population and may vary according to the stroke-related impairments. For example, in an individual with sensory or perceptual issues, the attentional demands of the audio-visual cue may be more significant.