## 2 Materials and Methods
### Data Analysis
#### 2.4.2 Isokinetic Strength Test  
Angular velocity (rad \(\times\) s\({}^{-1}\)) and torque (N \(\times\) m) were obtained from the isokinetic knee-extension strength test (ISO) (Figure 2a). The sampling rate was set at 1000 Hz. The torque signal was filtered using a second-order low-pass Butterworth filter with a cut-off frequency of 15 Hz. Zero-crossings of the angular velocity signal were used to identify the beginning and the end of each extension phase (Figure 2a). The mean torque for each repetition was subsequently calculated and the three values obtained were averaged. In order to assess the F-v relationship, torque (N \(\times\) m) and angular velocity (rad \(\times\) s\({}^{-1}\)) were converted into force (N) and linear velocity (m \(\times\) s\({}^{-1}\)). To do this, torque was divided by the length of individual lever arms and angular velocity was converted in rad \(\times\) s\({}^{-1}\) and multiplied by the length of individual lever arms [20]. Since the force-velocity relationship of single-joint tasks is considered to be approximately linear [20], the individual F-v relationship was assessed by fitting a linear regression  
\begin{table}
\begin{tabular}{l c c c c c c c c c} \hline  & \multicolumn{2}{c}{**Female**} & \multicolumn{2}{c}{**Male**} & \multicolumn{2}{c}{**Total**} & \multicolumn{2}{c}{_p-Value_} \\ \hline \# & & 21 & & & 25 & & 46 & & \\ Age (yrs) & 63.8 & \(\pm\) & 3.9 & 68.1 & \(\pm\) & 6.3 & 66.1 & \(\pm\) & 5.7 & 0.009 \({}^{*}\) \\ Weight (kg) & 65.7 & \(\pm\) & 12.1 & 81.2 & \(\pm\) & 16.6 & 74.1 & \(\pm\) & 16.5 & 0.001 \({}^{*}\) \\ Height (m) & 1.61 & \(\pm\) & 0.05 & 1.74 & \(\pm\) & 0.06 & 1.68 & \(\pm\) & 0.09 & \(<\)0.001 \({}^{*}\) \\ BMI (kg \(\times\) m\({}^{-2}\)) & 25.3 & \(\pm\) & 4.1 & 27.0 & \(\pm\) & 5.9 & 26.3 & \(\pm\) & 5.2 & 0.286 \\ WBLM (kg) & 39.4 & \(\pm\) & 5.0 & 55.1 & \(\pm\) & 8.9 & 48.4 & \(\pm\) & 10.8 & \(<\)0.001 \({}^{*}\) \\ d-LLM (kg) & 4.6 & \(\pm\) & 0.9 & 6.3 & \(\pm\) & 1.1 & 5.6 & \(\pm\) & 1.3 & \(<\)0.001 \({}^{*}\) \\ nd-LLM (kg) & 4.5 & \(\pm\) & 0.6 & 6.2 & \(\pm\) & 1.2 & 5.5 & \(\pm\) & 1.3 & \(<\)0.001 \({}^{*}\) \\ LLM (kg) & 9.1 & \(\pm\) & 1.5 & 12.5 & \(\pm\) & 2.3 & 11.0 & \(\pm\) & 2.6 & \(<\)0.001 \({}^{*}\) \\ SMI (kg \(\times\) m\({}^{-2}\)) & 4.9 & \(\pm\) & 0.6 & 5.9 & \(\pm\) & 1.0 & 5.4 & \(\pm\) & 1.0 & \(<\)0.001 \({}^{*}\) \\ Handgrip strength (kg) & 27.3 & \(\pm\) & 5.6 & 41.2 & \(\pm\) & 6.9 & 34.8 & \(\pm\) & 9.4 & \(<\)0.001 \({}^{*}\) \\ \hline \end{tabular} Mean \(\pm\) SD values of anagraphic, anthropometric, and strength variables, in females, males, and in the total group, BMI, body mass index; WBLM, whole-body lean mass; d-LLM, dominant lean leg mass; nd-LLM, non-dominant lean leg mass; LLM, lean leg mass; SMI, leg skeletal muscle index. The _p_-value of the unpaired t-test is displayed on the right side. * indicates a significant difference with females (F).  
\end{table}
Table 1: Anthropometrics, body composition, and clinical markers of muscle mass and strength of the sample.  
through the force and velocity data obtained from the five angular velocities tested (linear regression method) for each subject (Figure 2b). Maximum force (F0; force-intercept), maximum velocity (V0; velocity-intercept), and slope of the relationship (a = F0/V0) were detected. Finally, power and velocity values were fitted with a parabolic function (i.e., y = ax\({}^{2}\) + bx + c) for the computation of maximum power as the apex of the parabola (i.e., Pmax= \(-\) (b\({}^{2}\) - 4 ac) \(\times\) 4a\({}^{-1}\)) and the corresponding optimal velocity (Vopt= \(-\)b \(\times\) 2a\({}^{-1}\)). To fix the power-velocity relationship, the points of intersection of the parabola with the x-axis were added (at null velocity and V0, the power corresponds to zero) [21].