## 3 Results
### Results from the Human Subjects Testing
#### 3.2.5 Stance Phase  
The properties of prosthetic feet must promote early flat foot [97; 116]: this means that, the shorter the duration of the early stance, the sooner the flat foot phase begins. In order to calculate the length of the early stance, it is necessary to determine when the toe strike occurs. In fact, the early stance begins at 0% of the gait cycle and ends when the toe strike occurs. From the kinematic data, it is possible to determine when the toe strike occurs by determining when the inversion of the rotation of the foot around the ankle occurs, from plantarflexion to dorsiflexion. To understand how long the flat foot phase lasts, and therefore how long the stage in which the prosthetic foot performs a rotation of dorsiflexion accumulating elastic energy with its elastic elements, it is necessary to determine when the flat foot ends, i.e., when the heel-off takes place. As was the case for the determination of the end of the early stance (toe strike), the end of the midstance (heel-off) was found by determining the change of rotation of the foot from dorsiflexion to plantarflexion. Once \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Participant 1**} & \multicolumn{2}{c}{**Participant 2**} & \multicolumn{2}{c}{**Participant 3**} \\ \hline \hline \multicolumn{6}{c}{Step Length} \\ \hline Leg and prosthesis used & mean & std & mean & std & mean & std \\ \hline Healthy leg, own prosthesis & 0.534 m & 0.014 m & 0.357 m & 0.027 m & 0.554 m & 0.046 m \\ Healthy leg, MyFlex-\(\delta\) & 0.535 m & 0.015 m & 0.358 m & 0.020 m & 0.562 m & 0.018 m \\ Prosthetic leg, own prosthesis & 0.478 m & 0.022 m & 0.256 m & 0.019 m & 0.646 m & 0.030 m \\ Prosthetic leg, MyFlex-\(\delta\) & 0.471 m & 0.015 m & 0.242 m & 0.018 m & 0.624 m & 0.016 m \\ \hline \multicolumn{6}{c}{Prosthetic Leg Ankle Range of Motion/Healthy Leg Step Length} \\ \hline \hline \multicolumn{6}{c}{Prosthesis used} & mean & std & mean & std & mean & std \\ \hline Own prosthesis & 89.3\% & 4.8\% & 72.0\% & 7.9\% & 117.9\% & 17.3\% \\ MyFlex-\(\delta\) & 88.1\% & 3.2\% & 67.7\% & 6.6\% & 111.2\% & 4.7\% \\ \hline \multicolumn{6}{c}{Step Length Using MyFlex-\(\delta\)/Using their Own Prosthesis} \\ \hline Leg side & mean & std & mean & std & mean & std \\ \hline Healthy leg & 100.2\% & 3.7\% & 100.9\% & 10.0\% & 102.5\% & 15.3\% \\ Prosthetic leg & 99.0\% & 5.6\% & 94.9\% & 9.5\% & 96.7\% & 4.6\% \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Step Length. Mean values (mean) and standard deviations (std) are calculated from 50 gait cycles. Figure 15: Procedures for the calculation of: **(a)** the ratio between the step length measured from the prosthetic leg and the healthy leg; **(b)** the ratio between the step length measured while using MyFlex-\(\delta\) and while using a participant’s own prosthesis. again, the kinematic data in the sagittal plane were exploited. The end of the stance phase (toe-off) was determined in two ways: by calculating the ratio of contact time (parameter measured during human subjects testing) to stride time (also measured), or by determining the moment when the ground reaction force becomes zero (which means that the foot is no longer in contact with the ground). Toe strike, heel-off and toe-off events were calculated for each cycle. Once calculated, mean values and standard deviations were calculated for each of them. The calculated values are given in Table 8.  
Knowing that the early stance starts at 0% of the gait cycle and ends when the toe strike occurs, and already knowing when the toe strike occurs, it is easy to deduce how to calculate the duration of the early stance. Knowing for each cycle when the toe strike occurs and when the heel-off occurs, it is easy to also calculate the duration of the midstance. For each cycle, as well as for the early stance, the duration of the midstance was calculated, and subsequently mean values and standard deviations were calculated.