# Biomechanical Analysis of Running in Shoes with Different Heel-to-Toe Drops
## 3 Results  
The average speed of running across all participants was 4.0 \(\pm\) 0.2 m/s. No significant differences in step length or step frequency were detected when wearing shoes with different drops (\(p\) = 0.088, \(\mathrm{n_{p}}^{2}\) = 0.12; \(p\) = 0.563, \(\mathrm{n_{p}}^{2}\) = 0.04) (Table 1). A significant main effect of the drop of running shoes on the foot inclination angle at initial contact was detected (\(p\) = 0.001, \(\mathrm{n_{p}}^{2}\) = 0.36) (Table 1). Post hoc paired \(t\)-tests revealed that the foot inclination angle at initial contact was significantly greater when running in shoes with 15 mm, 10 mm, and 5 mm drops compared with running in shoes without a drop (\(p\) = 0.001; \(p\) = 0.001; \(p\) = 0.004). No significant differences in the knee flexion angle or ankle plantar flexion angle at initial contact were detected when running in shoes with different drops (\(p\) = 0.617, \(\mathrm{n_{p}}^{2}\) = 0.04; \(p\) = 0.418, \(\mathrm{n_{p}}^{2}\) = 0.05) (Table 1). No significant differences in the vertical impact peak or the vertical active peak were detected (\(p\) = 0.933, \(\mathrm{n_{p}}^{2}\) = 0.01; \(p\) = 0.506, \(\mathrm{n_{p}}^{2}\) = 0.04) (Table 1). A significant main effect of the drop of running shoes on the vertical loading rate was detected (\(p\) = 0.002, \(\mathrm{n_{p}}^{2}\) = 0.32) (Table 1). Post hoc paired \(t\)-tests revealed that the vertical loading rate was significantly lower when running in shoes with 15-mm and 10-mm drops compared with running in shoes without a drop (\(p\) = 0.005; \(p\) = 0.001). No significant difference in the vertical loading rate was detected between running in shoes with a 5-mm drop and without a drop (\(p\) = 0.030). A significant main effect of the drop of running shoes on the peak knee flexion angle was detected (\(p\) = 0.007, \(\mathrm{n_{p}}^{2}\) = 0.27) (Table 2). Post hoc paired \(t\)-tests revealed that the peak knee flexion angle was greater when running in shoes with 15-mm, 10-mm, and 5-mm drops compared with running in shoes without a drop (\(p\) = 0.012; \(p\) = 0.001; \(p\) = 0.003). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Variable**} & \multicolumn{4}{c}{**Heel-to-Toe Drop (mm)**} \\ \cline{2-5}  & **15** & **10** & **5** & **0** \\ \hline Running speed (m/s) & 4.0 \(\pm\) 0.1 & 4.0 \(\pm\) 0.2 & 4.0 \(\pm\) 0.2 & 4.0 \(\pm\) 0.1 \\ Step length (m) & 1.52 \(\pm\) 0.02 & 1.50 \(\pm\) 0.03 & 1.47 \(\pm\) 0.02 & 1.47 \(\pm\) 0.02 \\ Step frequency (steps/min) & 163.2 \(\pm\) 7.5 & 161.7 \(\pm\) 9.6 & 164.4 \(\pm\) 10.4 & 164.1 \(\pm\) 12.6 \\ Foot inclination angle at & 28.8 \(\pm\) 6.9 * & 28.3 \(\pm\) 7.6 * & 27.2 \(\pm\) 7.7 * & 22.6 \(\pm\) 8.5 \\ Vertical impact peak (BW) & 2.01 \(\pm\) 0.35 & 2.03 \(\pm\) 0.35 & 2.02 \(\pm\) 0.39 & 2.05 \(\pm\) 0.40 \\ Vertical loading rate & 67.1 \(\pm\) 15.2 * & 68.9 \(\pm\) 12.5 * & 72.9 \(\pm\) 14.2 & 85.2 \(\pm\) 19.1 \\ Vertical active peak (BW) & 2.73 \(\pm\) 0.32 & 2.70 \(\pm\) 0.33 & 2.69 \(\pm\) 0.28 & 2.75 \(\pm\) 0.33 \\ \hline \hline \end{tabular} Note: BW = body weight. * \(p\) < 0.017, significantly different from no heel-to-too drop.  
\end{table} 
Table 1: Comparison of spatiotemporal parameters and impact force among the four shoe conditions. A significant main effect of the drop of running shoes on the peak knee extension moment was detected (\(p\) = 0.002, \(\eta_{\mathrm{p}}\)\({}^{2}\) = 0.27) (Table 2). Post hoc paired \(t\)-tests revealed that the peak knee extension moment was greater when running in shoes with 15-mm and 10-mm drops compared with running in shoes without a drop (\(p\) = 0.015; \(p\) = 0.003). No significant difference in the peak knee extension moment was detected between the running shoes with a 5-mm drop and those without a drop (\(p\) = 0.072). A significant main effect of the drop of running shoes on the peak ankle version angle was detected (\(p\) = 0.002, \(\eta_{\mathrm{p}}\)\({}^{2}\) = 0.29) (Table 2).