## 3 Experiment
### Measurement and Evaluation  
The physiological data were set as the sEMG of the tibialis anterior, measured by a TrignoTM Wireless System (Delsys Inc., Natick, MA, USA) sampled at 2000 Hz. The data were analyzed by EMG works (Delsys Inc., Natick, MA, USA). According to the studies on lower-limb sEMG processing and analysis [35; 36], the collected data were filtered with a fourth-order Butterworth bandpass filter, and cut-off frequencies were set between 20 and 450 Hz. Before the experiment, each participant's maximum voluntary contraction (MVC) was collected. After filtering, the MVC data were processed by root mean square with a 300 ms movable window. The collected data in the experiment were filtered and processed by amplitude analysis, and the evaluation index was set as the maximum percentage referencing the processed MVC data during the swing phase. The index was regarded as the extent of voluntary dorsiflexion.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Participant** & **Gender** & **Age (Years)** & **Height (cm)** & **Weight (kg)** \\ \hline A & Male & 26 & 170 & 70 \\ B & Female & 24 & 163 & 53 \\ C & Male & 24 & 172 & 102 \\ D & Female & 23 & 166.5 & 50.5 \\ E & Male & 25 & 175 & 100 \\ F & Male & 32 & 172 & 76 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Information of the participants.  
Figure 5: The dorsiflexion-restricted orthosis.  
The kinematic data were measured and collected with a motion capture system (MAC3D, NAC Inc., Japan) consisting of eight high-speed cameras. The sampling rate for data collection was set at 200 Hz. Figure 5(a) shows a photo of the reflection markers placed on a participant's body, and Figure 5(b) illustrates the marker setting:  
* RHEEL, LHEEL: Heels on both feet;
* RMT1, LMT1: First metatarsal bones in both feet;
* RMT5, LMT5: Fifth metatarsal bones in both feet;
* RTIB, LTIB: Middle of tibias of both legs;
* RFIB, LFIB: Middle of fibulas of both legs;
* RKNE, LKNE: Patellas of both legs;
* RTHI, LTHI: Middle of lateral thighs of both legs;
* RHIP, LTHI: Greater trochanter of both legs;
* RCRE, LCRE: Iliac crests of both sides;
* RASIS, LASIS: Anterior superior iliac spines of both sides;
* SACR: Sacrum.  
After low-pass filtering with a cut-off frequency at 6 Hz, the recorded data were analyzed by nMotion musculus (NAC Inc., Tokyo, Japan) to derive gait parameters including lower-limb joint angles. Due to the placement of the dorsiflexion-restricted AFO, the markers could not be placed at the ankle joints. With nMotion musculus's lower-limb model, the ankle joint angles could still be calculated with the markers set from toe to knee.  
Evaluation indices for kinematic data include swing-phase dorsiflexion angle, limb shortening in the swing phase, swing width, and hip hike. Swing-phase dorsiflexion angles were calculated by nMotion musculus. The other indices are illustrated in Figure 7. Limb shortening was defined as the decrease in distance between the hip joint to the forefoot in the swing phase compared with that in a standing posture, calculated as the distance between the RHIP and RMT5 markers. Extent of circumduction and hip hiking was evaluated by swing width and hip hike, which are the expected compensatory movements if ankle dorsiflexion or limb shortening in the swing phase is insufficient. Swing width was defined as the RMT1 marker's lateral swing distance in the swing phase, and hip hiking was defined as the RHIP marker's ascent in the swing phase.  
Figure 6: (a) A photograph of markers placed on a participant; (b) the marker set in this research.