## 3 Results  
The general characteristics of the subjects are shown in Table 1. The average age was 23.7 years old (21-31 years), average height was 169.4 cm (158-185 cm), average weight was 64.35 kg (50-100 kg), and average body mass index (BMI) was 22.3 (19.53-29.22 kg/m\({}^{2}\)).  
The position (ES = 3.03), sum distance (ES = 3.05), range (ES = 6.31), and max distance (ES = 5.39) significantly (\(p<0.05\) unless stated otherwise) differed among the three positions. The outcomes of the CoP in the HADF were all negative values; in contrast, the outcomes of the CoP in the HABF and HNEF were positive values. Judging from the size of the numbers, the HABF produced significantly higher CoP outcomes than the HADF and HNEF in terms of position, sum distance, range, and max distance. The HNEF showed significantly higher CoP outcomes than the HADF (Table 2) (Figure 3).  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Characteristics** & **Mean \(\pm\) SD 1** \\ \hline Age (yr) & \(23.7\pm 2.51\) \\ Height (cm) & \(169.4\pm 7.8\) \\ Weight (kg) & \(64.3\pm 12.7\) \\ Body mass index (kg/m\({}^{2}\)) & \(22.26\pm 2.48\) \\ \hline \hline \end{tabular} \({}^{1}\)Mean \(\pm\) standard deviation.  
\end{table}
Table 1: General characteristics of subjects.  
Figure 2: Measurement of CoP and muscle activity of VMO and VL: (**a**) hip abduction forward lunge; (**b**) hip neutral forward lunge; (**c**) hip adduction forward lunge.  
The movement trajectories of the CoP for the three postures within 5 s at intervals of 1 ms showed that most of the outcomes of the CoP in the HADF were negative numbers; on the contrary, most of the CoP outcomes in the HABF were positive numbers. The movement trajectories of the CoP in the HNEF first analysis showed negative numbers and then positive numbers (Figure 4).  
The VMO (ES = 1.71) and VL (ES = 0.53) muscle activity and the ratio of VMO/VL (ES = 1.27) significantly differed among the three positions. In the VMO, the HADF produced significantly higher muscle activity (58.30 \(\pm\) 14.42% MVIC) than the HABF and HNEF. The HABF (45.28 \(\pm\) 16.23% MVIC) showed significantly higher muscle activity than the HNEF (34.88 \(\pm\) 9.49% MVIC). In the VL, the HABF produced significantly higher muscle activity (48.44 \(\pm\) 16.19% MVIC) than the HADF and HNEF. The HADF (40.98 \(\pm\) 12.64% MVIC) showed significantly higher muscle activity than the HNEF (33.79 \(\pm\) 11.57% MVIC). In the ratio of VMO/VL, the HADF produced significantly higher muscle activity (1.48 \(\pm\) 0.31) than the HABF and HNEF. In addition, the HNEF (1.11 \(\pm\) 0.33) showed significantly higher muscle activity than the HABF (0.96 \(\pm\) 0.23) (Table 3) (Figure 5).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & **HADF 1** & **HNEF 2** & **HABF 3** & **F** & **_p_ & **ES 4** \\ \hline position (cm) & \(-0.85\)\(\pm\) 0.80 & \(0.02\)\(\pm\) 0.38 & \(0.98\)\(\pm\) 0.55 & 48.325 & \(0.001\) \({}^{\star}\) & 3.03 \\ sum distance (cm) & \(-428.34\)\(\pm\) 399.33 & \(10.44\)\(\pm\) 189.78 & \(488.97\)\(\pm\) 276.76 & \(48.739\) & \(0.001\) \({}^{\star}\) & 3.05 \\ range (cm) & \(-2.28\)\(\pm\) 0.62 & \(1.52\)\(\pm\) 0.77 & \(2.25\)\(\pm\) 0.75 & \(240.859\) & \(0.001\) \({}^{\star}\) & 6.31 \\ max distance (cm) & \(-1.85\)\(\pm\) 0.76 & \(0.66\)\(\pm\) 0.57 & \(1.89\)\(\pm\) 0.73 & \(158.708\) & \(0.001\) \({}^{\star}\) & 5.39 \\ \hline \end{tabular} \({}^{1}\) Hip aduction forward lunge. \({}^{2}\) Hip neutral forward lunge. \({}^{3}\) Hip abduction forward lunge. \({}^{4}\) Effect size.  
\({}^{\star}\) Significant difference between groups (_p_ < 0.05).  
\end{table}
Table 2: Comparison of variation in CoP between three positions.  
Figure 4: Example of movement trajectory of CoP within five seconds: (**a**) hip abduction forward lunge; (**b**) hip neutral forward lunge; (**c**) hip aduction forward lunge.  
Figure 3: Comparison of variation in CoP between three positions: (**a**) position; (**b**) sum distance; (**c**) range; (**d**) max distance. \({}^{\star}\) Significant difference between groups (_p_ < 0.05).