## 3 Results
### Changes in Muscle Activity According to the Local Vibratory Stimulation Conditions  
Figures 2 and 3 show patterns of muscle activity according to the local vibratory stimulation conditions. Tables S1 and S2 show the mean and standard deviations of the vibrational stimulus conditions according to the gait phase, and the statistical significance between the conditions (See Supplementary Material).  
At the threshold intensity, TA showed that Min was lowest at 16.4% in the PU phase (Table S1), and that the amplitude of Max and Min decreased in the swing phase (FC and FP phase) faster than that of None. GL showed that Min had the highest peaks at 87.6% compared with other vibratory conditions in FCN phase, and for GM and SOL we could not confirm a difference due to vibratory conditions.  
\begin{table}
\begin{tabular}{c|c|c|c|c|c|c|c|c|c|c|c|c} \hline
**Frequencies** & **100 Hz** & **120 Hz** & **140 Hz** & **160 Hz** & **180 Hz** & **190 Hz** & **200 Hz** & **210 Hz** & **220 Hz** & **240 Hz** & **250 Hz** & **260 Hz** \\ \hline
**100 Hz** & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & & & & & & & & \\ \hline
120 Hz & & & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & & & & & \({}^{*}\) \\ \hline
140 Hz & & & & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) \\ \hline
**160 Hz** & & & & & & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) \\ \hline
**180 Hz** & & & & & & & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & & \\ \hline
190 Hz & & & & & & & \({}^{*}\) & \({}^{*}\) & & & \\ \hline
200 Hz & & & & & & & & \({}^{*}\) & & & & \\ \hline
210 Hz & & & & & & & & & & & \({}^{*}\) & \({}^{*}\) \\ \hline
220 Hz & & & & & & & & & & & & \\ \hline
240 Hz & & & & & & & & & & & & \\ \hline
250 Hz & & & & & & & & & & & & \\ \hline
260 Hz & & & & & & & & & & & & \\ \hline \end{tabular} \({}^{*}\) Indicates statistical significance between vibration frequencies (\(p<0.05\)).  
\end{table}
Table 1: Result of paired \(t\)-test of the mu rhythm reduction rate, \({}^{*}\) indicates a statistical significance between vibrational frequencies (\(p<0.05\)).  
Figure 1: Mean (\(\pm\) standard deviation) of mu rhythm reduction rate (through paired \(t\)-test) according to localized vibration frequencies.  
At sub-threshold intensity, Tibialis anterior muscle (TA) showed lower activity in Max (15%) and Min (13.4%) than in None during the PU phase (Table S2). The maximum peak appeared in the FC phase (Figure 3a). Early decreases in the EMG activity were observed in the FP phase. The triceps muscle of the calf (i.e., GL, GM, and SOL) showed enhanced peak activity under all vibratory conditions, and muscle activity was increased between the PU and the FCN phases (Figure 3a-c).  
Figure 2: Mean of electromyogram (EMG) activity of all participants in the vibrational stimulation conditions at the threshold intensity: (**a**) Tibialis Anterior (TA), (**b**) Gastrocnemius Lateralis (**c**) Gastrocnemius Medialis (GM), (**d**) Soleus (SOL). ’Th-Max’ means a vibration of 140 Hz was applied at the threshold intensity, while ’Th-Min’ means a vibration of 210 Hz was applied at the threshold intensity. The solid line indicates the gait phase (Weight Acceptance (WA, 0%-14%), Pull-Up (PU, 15%-32%), Forward Continuance (FCN, 33%-64%), Foot Clearance (FC, 65%-82%), Foot Placement (FP, 83%-100%)).