## 4 Discussion  
The first aim of the present study was to investigate the feasibility and validity of the 5 STS test compared to the ISO test to assess maximum force, velocity, and power through F-v and P-v profiling in older adults. The second aim was to investigate the relationship between maximum force and power with markers of muscle mass and strength that are typically used in a clinical setting. The main findings of the present study are as follows: (i) 5 STS profiling is a feasible and valid alternative to isokinetic testing for the characterization of muscle function in healthy older adults of both sexes; (ii) while the absolute values of maximum force and maximal and optimal velocity are significantly different between the two tests, the maximum power values measured in 5 STS and ISO are similar and highly correlated; (iii) both maximal muscle strength and power are significantly and highly correlated with the most commonly used clinical markers of muscle mass and strength. In our study, the feasibility of the 5 STS test in terms of safety performing the protocol and building a proper F-v and P-v profile was verified. In fact, all participants completed all the trials for both ISO and 5 STS tests without experiencing any adverse outcomes. Furthermore, the R\({}^{2}\)mean of F-v profiling in 5 STS (0.97 \(\pm\) 0.03) was high and similar (\(p\) = 0.581) to the ISO (0.97 \(\pm\) 0.03). Moreover, the values for 5 STS are similar to the R\({}^{2}\)mean presented in the literature for other lower limb multi-joint exercises performed by older adults (e.g., leg press, R\({}^{2}\)mean from 0.95 to 1.00) of both sexes [10]. These results suggest that it is possible to use the 5 STS test not only as a generic screening tool but, in its modified version which includes the use of overloads, for the full characterization of muscle function. The values of F0 from ISO are typically presented in the literature in peak torque units [5; 26; 27]. However, as our study focused on the comparison of F0 between ISO and 5 STS tests, we used mean rather than peak data and converted torque and angular velocity from ISO into force and linear velocity [20; 28]. For these reasons, direct comparison with the literature data may be difficult. To the best of our knowledge, only [PERSON] et al. [20] presented F0 values for the isokinetic test in Newton units derived from both peak and mean values. The above study conducted in young females found F0 values (\(\sim\)350 N) similar to those observed in the present study (309 \(\pm\) 78N). When our F0 values are converted into torque units (by multiplying force by the mean lever arm) the values found in our study (309 N \(\times\) 0.34 m= 105 N \(\times\) m) are lower than the literature (\(\sim\)155 N \(\times\) m) in a comparable \begin{table}
\begin{tabular}{l c c c c c} \hline \hline  & \multicolumn{2}{c}{**F0 (N)**} & \multicolumn{2}{c}{**Pmax (W)**} & \multicolumn{2}{c}{**Handgrip**} \\ \cline{2-6}  & **ISO** & **5 STS** & **ISO** & **5 STS** & **Strength (kg)** \\ \hline
**WBLM (Kg)** & 0.75 & 0.73 & 0.84 & 0.81 & 0.74 \\
**d-LLM (Kg)** & 0.69 & 0.70 & 0.81 & 0.78 & 0.68 \\
**LLM (Kg)** & 0.71 & 0.71 & 0.82 & 0.79 & 0.68 \\
**SMI (kg \(\times\) m\({}^{-2}\))** & 0.66 & 0.69 & 0.74 & 0.65 & 0.50 \\
**Handgrip strength (kg)** & 0.70 & 0.53 & 0.74 & 0.75 & 1.00 \\ \hline \hline \end{tabular} Pearson’s correlation coefficients between the indicated variables as measured in the isokinetic strength test (ISO) and the 5 5t-to-Stand test (5 STS) are reported: F0, maximum force; Pmax, maximum power; WBLM, whole-body lean mass; d-LLM, dominant lean leg mass; LLM, lean legs mass; SMI, leg skeletal muscle index.  
\end{table} 
Table 4: Correlation coefficients between strength and power indexes and clinical markers of muscle mass and strength. population [5; 26; 27]. This may be due to the fact that we used mean rather than peak values for F-v profiling. To the best of our knowledge, only [PERSON] et al. investigated F0 derived from STS movement [12].