# Effects of Toe-Out and Toe-In Gaits on Lower-Extremity Kinematics, Dynamics, and Electromyography
## 2 Methods  
### Experimental Data  
Twelve healthy participants (6 males and 6 females) were recruited in this study; the mean values of the participants are as follows: age \(24.3\pm 2.12\) years old, weight \(57.6\pm 11.58\) kg, height \(1.7\pm 0.07\) m, and BMI \(19.8\pm 2.67\) kg/m\({}^{2}\). All participants have no history of lower-extremity injury that required surgery and no joint instability phenomenon within the previous six months. The study was approved by the University Research Ethics Committee, Taiyuan University of Technology, and all participants agreed to and signed consent forms for the study.  
Three-dimensional body motion was recorded by using the 10-camera Vicon system and 16 light-reflecting skin markers of 14-mm diameter, with a sampling frequency of 100 Hz. The Vicon Plug-in Gait markers were attached at anatomical landmarks of the lower extremity; upper limb kinematic data were not collected. Detailed information on the markers and the surface EMG locations are shown in Figure 1a; the locations of the markers were selected based on the anatomical skeleton landmarks with the help of an orthopedist. Prior to attaching the markers, anthropometric measurements (leg length, knee width, and ankle width) were taken for scaling and establishing the lower-extremity model in the Vicon system. After attaching surface markers, EMG data of nine muscles (rectus femoris, vastus medialis, vastus lateralis, peroneus longus, tibialis anterior, semitendinosus, biceps femoris, gastrocnemius medialis, and gastrocnemius lateralis) surrounding the right knee were sampled at 1500 Hz using surface electrodes to qualitatively compare muscle activations that are directly related to muscle forces [28; 29]. EMG electrode locations of the muscles were identified from the muscle belly or muscle orientation; participants were asked to make specified postures and to touch the muscles by hand. Prior to application of electrodes, selected sites were shaven, abraded, and cleaned with alcohol based on published guidelines [30]. GRF data were collected synchronously at 1500 Hz using three AMTI force plates embedded in the laboratory floor during the gait trials and a metronome-controlled frequency of approximately 1.58 Hz (95 steps/min), which was chosen after measuring subjects' walking speed. Three gait patterns including natural, toe-in, and toe-out were selected and measured to understand their influence on lower-extremity joint kinematics, dynamics, and muscle forces [9; 10; 31]. To control the FPA of participants, prior to collecting each gait pattern data, the participants were asked to adapt their FPA to the required angles for the toe-in and toe-out gait patterns, which are shown Figure 2; the FPA were marked on the floor with white tapes. Five trials were conducted for each gait pattern. The study hypothesized that the FPAs of the five trials for each gait were consistent and would not affect the validity of the results.  
Figure 1: (**a**) Surface markers (blue circle) and electromyography (EMG) electrodes (red circle) used for trials and (**b**) musculoskeletal model of the lower extremity.