## 2 Materials and Methods
### Data Collection  
First, the experimental process was explained to the participants and they signed the relevant questionnaire and informed consent. The same uniform sportswear was replaced, and forty infrared retroreflective markers (diameter: 14.0 mm) were attached bilaterally to both of the lower extremities to define hip, knee, and ankle joints according to the plug-in gait marker set [12]. Before the experiment, the participants performed a 5-min warm-up on a treadmill at an optional running speed only with cushioned shoes, followed by a 1-minute 3.33 m/s experimental speed adaptation. Meanwhile, it was the first time that they had worn minimalist shoes, which was considered as \"immediately\". After completing the preparation, the participants began the formal experimental tests.  
Two \(90\times 60\times 10\) cm Kistler 3D force platforms (9287B, Kistler Corporation, Switzerland) were used to collect ground reaction force (GRF) data at a sampling rate of 1000 Hz. A 10-camera infrared 3D motion capture system (Vicon T40, Oxford Metrics, UK) was used to collect the trajectory markers (14.0 mm in diameter) of the bone landmarks of the lower extremities to define the knee joint at a sampling rate of 100 Hz (Figure 2). The participants randomly wore one of the shoes. A 5-10 minute break was provided between two shoe tests to eliminate the potential interference. Three running trials were collected per condition at 3.33 m/s (\(\pm\)5%). This target speed was common for recreational runners and all participants completed running trials without any discomfort. Running speed was monitored by the use of a Witty-Manual grating timing system (Micro gate, Italy) positioned 4 m apart along a 20 m runway. Meanwhile, the participants were required to run back and forth until three successful steps (trials) in which the foot of the dominant lower extremity (defined as preferred kicking  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Shoe** & **Weight (g)** & \begin{tabular}{c} **Stack Height** \\ **(mm)** \\ \end{tabular} & \
\begin{tabular}{c} **Heel-to-Toe** \\ **Drop (mm)** \\ \end{tabular} &
\begin{tabular}{c} **Stability and Motion** \\ **Control Technologies** \\ \end{tabular} & **Flexibility** & **MI (\%)** \\ \hline INOV-8 Bare-XF & & & & & & \\
210 V2 & & & & & & \\ Subscore & 2 & 5 & 5 & 5 & 4.5 & \\ \hline Nike Air Zoom & & & & & & \\ Pegasus 34 & & & & & & \\ Subscore & 1 & 1 & 2 & 1 & 1.5 & \\ \hline \hline \end{tabular}  
* Notes: Four stability and motion control technologies of the Nike Air Zoom Pegasus 34: multi-density midsole, rigid heel counter, supportive tensioned medial upper and medial flare. MI = sum of subsocre \(\times\) 4 \(\times\) 100%.  
\end{table}
Table 1: Detailed comparison of the Minimalist Index (MI) of the two shoes.  
Figure 1: Shoes used in the experiment. Minimalist shoe: INOV-8 Bare-XF 210 V2 (**left**). Cushioned shoe: Nike Air Zoom Pegasus 34 (**right**).  
leg [13]) was completely on the force plate were collected for each shoe condition. Each trial that met the following criteria was deemed successful: 1) The speed was 3.33 m/s (\(\pm\)5%) within the capture volume; 2) no relative sliding occurred between the shoes and the force plate.