## 4 Discussion  
The purpose of this study was to assess the mechanical properties of two subjective categories of running shoe--minimalist and cushioned--and then to compare the spatiotemporal and kinetic variables of gait in habituated female runners at treadmill speeds of 6, 10, and 14 km\(\cdot\)h\({}^{-1}\). The key findings indicate that the cushioned shoe exhibited \begin{table}
\begin{tabular}{l c c c c c c} \hline
**Shoe** & **Minimalist** & **Cushion** & **Minimalist** & **Cushion** & **Minimalist** & **Cushion** \\ \hline Speed (km\(\cdot\)h\({}^{-1}\)) & 6 & 6 & 10 & 10 & 14 & 14 \\ \hline Stride Duration & \(1.2\pm 0.3\) & \(1.1\pm 0.3\) & \(1.0\pm 0.2\) & \(1.2\pm 0.4\) & \(1.1\pm 0.3\) & \(1.1\pm 0.3\) \\ \hline Stride Frequency & \(1.3\pm 0.3\) & \(1.3\pm 0.4\) & \(1.0\pm 0.2\) & \(1.2\pm 0.4\) & \(1.1\pm 0.3\) & \(1.1\pm 0.3\) \\ \hline Ground Contact Time & \(1.7\pm 0.5\) & \(2.4\pm 1.3\) & \(4.6\pm 0.7\) & \(4.6\pm 0.8\) & \(4.6\pm 1.7\) & \(5.0\pm 1.2\) \\ \hline Swing Time & \(3.8\pm 0.7\) & \(4.3\pm 1.4\) & \(3.5\pm 0.6\) & \(3.2\pm 0.8\) & \(3.8\pm 2.0\) & \(3.7\pm 1.4\) \\ \hline Peak Impact Force & \(3.5\pm 1.4\) & \(3.2\pm 0.8\) & \(7.1\pm 1.0\) & \(7.0\pm 2.1\) & \(6.8\pm 1.8\) & \(6.5\pm 1.1\) \\ \hline Loading Rate & \(13.6\pm 4.8\) & \(11.2\pm 2.3\) & \(10.1\pm 2.4\) & \(11.4\pm 3.0\) & \(8.4\pm 1.9\) & \(7.4\pm 0.9\) \\ \hline Active Peak Force & \(2.9\pm 1.7\) & \(2.8\pm 0.8\) & \(1.6\pm 0.4\) & \(2.2\pm 0.5\) & \(1.9\pm 0.4\) & \(2.6\pm 0.7\) \\ \hline Time to Active Peak Force & \(2.3\pm 0.6\) & \(5.7\pm 0.5\) & \(6.1\pm 1.8\) & \(7.3\pm 2.4\) & \(5.7\pm 1.5\) & \(6.3\pm 2.4\) \\ \hline Impulse & \(2.4\pm 0.6\) & \(2.7\pm 1.0\) & \(3.1\pm 0.4\) & \(2.8\pm 0.4\) & \(2.7\pm 1.0\) & \(2.8\pm 0.9\) \\ \hline \end{tabular}
\end{table} 
Table 1: The overall mean \(\pm\) SD for the CV(%) for each trial (speed*shoe) for all dependent variables. Figure 4: Mean \(\pm\) SD data for each treadmill speed (6, 10, and 14 km\(\cdot\)h\({}^{-1}\)) whilst wearing minimalist and modern-day cushioned shoes for (**A**) stride duration (s), (**B**) ground contact time (s), (**C**) midstance time (s), and (**D**) swing time (s), where is the minimalist shoe and is the cushioned shoe. * Indicates significant interaction (speed*shoe), and indicates post hoc significance between shoes. Symbol number indicates significance level, e.g., * \(p\) \(<\) 0.05, *** \(p\)\(<\) 0.0001, \(\bigstar\)\(\bigstar\)\(\bigstar\)\(p\)\(<\) 0.0001.  
greater energy absorption (690%), recovered energy (920%), and heat dissipation (350%). These mechanical property differences resulted in the cushioned shoes significantly reducing the peak vertical impact (\(\sim\)12%) and average loading rate (\(\sim\)11%) at running speeds of 10-14 km\(\cdot\)h\({}^{-1}\), while not affecting peak active force, impulse, stride duration, ground contact or swing time during walking or running. As expected (Figure 4) and supported by prior research, increased speed led to higher running cadence [54] due to decreased ground contact time, time to mid-stance, and swing time [55]. Additionally (Figure 3), higher speeds resulted in increases in peak vertical impact, average loading rate, and active vertical peak force, along with a decreased time to active vertical peak force [9; 11; 13; 56]. These kinetic variables have also been associated with running-related injuries [5; 7], implicating running speed as a factor in injury aetiology [57]. Understanding strategies to attenuate impact-related metrics is crucial as walkers and runners increase their speed [12]. One such strategy involves the mechanical properties of shoe midsoles, particularly energy absorption (cushioning) and energy recovery [58; 59]. The data presented in Figure 2 shows two very different shoe types acquired during 2023 (Figure 1). Although there is no standardised classification for shoe cushioning, the 690% difference in energy absorption capability suggests that one of the shoes used provides much greater cushioning compared to the other.