## 2 Materials and Methods
### Data Analysis
#### 2.4.3 STS Test  
Vertical force, position, and velocity were extrapolated from kinetic and kinematics data of the SSTS test in each of the four different weight conditions (Figure 3a). The sampling rate was set at 1000 Hz and 100 Hz, and a second-order low-pass Butterworth filter was used for both signals (frequency cut = 7 Hz and 20 Hz, respectively). Vertical velocity was used to recognize the repetitions and each concentric and eccentric phase. Then, positive and negative peaks of vertical velocity were identified, and thresholds were calculated as 5% of the peaks. The start and end of repetition were found when the vertical velocity reached the positive and negative threshold, respectively. Finally, the end of the concentric phase was defined when vertical velocity crossed zero after a positive peak (Figure 3a) [22]. For our purpose, only the concentric phases (i.e., the standing phases) were considered to calculate mean concentric vertical velocity and mean concentric vertical force [10], and the five values obtained from repetitions were averaged [23]. As a linear equation was expected from the F-v relationship of multi-joint movement [21], when a mean concentric vertical velocity of a repetition differed by more than 0.03 m \(\times\) s\({}^{-1}\) from the estimated value (based on linear regression), the repetition was removed. If all five repetitions differed by more than 0.03 m \(\times\) s\({}^{-1}\), the trial was deleted [10].  
Figure 2: (**a**) Graph of the isokinetic knee-extension strength test at 1.05 rad \(\times\) s\({}^{-1}\) in a representative subject. Torque (N \(\times\) m; solid line — ), and angular velocity (rad \(\times\) s\({}^{-1}\); dotted line \(\cdots\)) are plotted in function on time (s). Knee extension (light grey area) and flexion (dark grey area) phases were identified when angular velocity was negative and positive, respectively. The start (\(\bullet\)) and the end (\(\blacksquare\)) of knee extension repetitions were reported where angular velocity crosses zero. Peaks of torque (\(\Circ\)) were found for each knee extension. In (**b**) force–velocity (\(\bullet\) F-v) and power–velocity (\(\Circ\) P-v) relationship of the 5 Sit-to-Stand test in a representative subject are reported. Maximum force (\(\blacklozenge\) F0) corresponds to the intercept with the y-axis where velocity is null; maximum velocity (\(\blacksquare\) V0) corresponds to the intercept with the x-axis where force is null; maximum power (\(\Diamond\) Pmax) represents the apex of the power–velocity curve; optimal velocity (\(\square\) Vopt) is the velocity at maximum power.  
Then, it was possible to fit the individual force-velocity and power-velocity relationships for each subject (Figure 3b). All parameters of interest (F0, V0, a, Pmax, and Vopt) were identified with the same method used for isokinetic strength measurements (see above). Finally, in order to facilitate the direct comparison between ISO and 5 STS tests, single-leg STS force and power were estimated by adding 23% and 20% of the total, respectively (to consider the bilateral deficit [8]), and then dividing by 2.  
All signal analyses of ISO and 5 STS tests were performed by MatLab (Version R2021B, MathWorks Inc., Natick, MA, USA) scripts, and the results were exported to an Excel (Microsoft 365, Version 16.0.16501.20228, Microsoft Corporation, WA, USA) spreadsheet with the anthropometric and body composition measures for subsequent calculations.