## 4 Discussion  
The study aimed to investigate the test-retest reliability of knee HAs dispersion indexes during walking in healthy subjects and assess the effects of maximal versus resistant strength training on knee HAs dispersion during walking in healthy subjects. In our study, knee HAs dispersion indexes revealed moderate to excellent test-retest reliability on the sagittal plane, whereas reliability decreased for HAs parameters on the transverse and frontal planes. Moreover, a 2-week maximal or resistant strength training of the quadriceps and hamstring muscles induced no knee HAs dispersion changes during walking in healthy subjects. This was the first study addressed to investigate the reliability of knee HAs dispersion parameters during walking, showing higher reliability on the sagittal plane. The current findings may be related to larger knee excursion along the sagittal plane during walking, which resulted in a large number of computed HAs and high reliability in the estimation of the dispersion indexes [30; 31]. In fact, in agreement with previous studies, HAs were computed every 10\({}^{\circ}\) of knee motion along the sagittal plane, in order to adopt an angle step able to provide a good compromise between movement analysis resolution and error in HAs estimation [9; 26]. Consequently, this technique implied the assignment of a limited number of HAs to the frontal and transverse planes, where the range of motion is limited. In fact, it is worth noting that reliability consistently decreased according to the percentage of \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **RT Group (\(n\) = 15)** & **MT Group (\(n\) = 15)** & \(p\)**-Value** \\ \hline \multicolumn{4}{c}{Variables} \\ \hline Age (years) & 22.5 \(\pm\) 1.4 & 22.8 \(\pm\) 2.7 & 0.739 \\ Weight (kg) & 66.3 \(\pm\) 15.2 & 63.0 \(\pm\) 12.4 & 0.524 \\ Height (cm) & 173.5 \(\pm\) 12.1 & 173.0 \(\pm\) 8.8 & 0.905 \\ Gender (M/F) & 7 M/8 F & 7 M/8 F & 1.000 \\ Dominant limb (R/L) & 15 R/0 L & 15 R/0 L & 1.000 \\ \hline \multicolumn{4}{c}{**Abbreviations: M: male, F: female, R: right, L: left.**} \\ \end{tabular}
\end{table} 
Table 2: Participants’ characteristics for RT and MT groups (independent sample t-tests and chi square tests). Data are shown as the mean \(\pm\) the standard deviation. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & & & & & & & & & & & & & \\ \cline{3-13} \multirow{-2}{*}{**Outcome**} & \multirow{-2}{*}{**Phase**} &  
computed HAs, where higher HAs percentage on a plane seems to lead to higher accuracy in HAs parameters estimation (sagittal \(>\) transverse \(>\) frontal) [31]. Moreover, higher intra-subject variability in terms of knee kinematics has been described in healthy subjects on the frontal and transverse planes, when compared to the sagittal plane. This phenomenon may represent an additional influencing factor on the reliability of HAs dispersion parameters, especially when a limited number of steps are considered [30,32,33]. Based on reliability results, HAs assigned to the sagittal plane were exclusively considered to investigate the effects of maximal versus resistant strength training on knee HAs dispersion. No between-groups differences in terms of HAs dispersion were found during walking in healthy subjects, except for MA, which was lower in the MT group after the first training session and at training end in the first phase of the gait cycle. During this gait phase, knee is slightly flexed and a horizontal component of the ground reaction force results in considerable translational external moment [34]. This timeframe is particularly demanding in terms of neuromuscular control, which plays a key role in contrasting this moment and ensuring stability [34,35]. When considering our results, higher controlled knee kinematics seemed to occur in the MT group after a single training session and at the training end.