## 4 Discussion  
The results presented herein confirmed the well-known relationship between muscle mass and muscle quality parameters measured by BIA with rehabilitation outcome in post-stroke patients. Additionally, we found that BCM measured at admission may be a novel biomarker for the evaluation of post-stroke rehabilitation treatment. In fact, BCM T0 is not only positively correlated with baseline ADL performance, but it is also positively associated with patients' recovery, regardless of their performance at admission. After a stroke insult, there could be an impairment in body composition [12], so the BIA analysis may be helpful in determining the proper rehabilitation and nutrition management in post-stroke patients [13]. As recently published, lean body mass at admission, especially muscular tissue, plays a role in surviving from stroke [13]. A muscle healthy condition is crucial for the recovery: muscle mass deficit, in terms of lower value of skeletal muscle index (SMI), has been proven to be an independent poor outcome predictor in acute stroke patients [17]. Moreover, stroke-related sarcopenia, which is a condition characterized by loss of muscle strength, mass, and function, had a negative effect on functional recovery [19, 23], whereas its improvement corresponds to a better functional outcome [20]. Another commonly measured BIA-derived parameter is PhA, which it is associated with cell membrane integrity, cells function, and hydration [39]. Recent research examined the importance of PhA as a biomarker for the evaluation for the diagnosis of malnutrition/undernutrition [42] and of the effectiveness of rehabilitation treatment in post-stroke patients [24, 26, 27]. Our study confirmed the actual link between lean and muscle mass and muscle quality and functional status at baseline in subacute post-stroke patients admitted to rehabilitation. In fact, the FFM, ASMM, and their relative indices (height-squared-adjusted: FFMI, SMI), as well as PhA were positively correlated with the ADL at baseline. On the other hand, there was no correlation between the baseline ADL and any of the fat mass-related measurements. Even though PhA between two groups is not significantly different, it is important to note that the PhA mean values in both groups were under the normal range, indicating a muscle quality impairment. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**BI T0**} & \multirow{2}{*}{\(B\)} & \multicolumn{3}{c}{**95\% CI**} & \multirow{2}{*}{\(\mathbf{SE}\ B\)} & \multirow{2}{*}{\(P\)} & \multirow{2}{*}{\(\mathbf{R^{2}}\)} & \multirow{2}{*}{\(\Delta\mathbf{R^{2}}\)} \\ \cline{5-6}  & & & \(LL\) & & & & \\ \hline  & & & & & & 0.23 & 0.24 \\ BCM T0 & 0.78 & 0.03 & 1.52 & 0.37 & **0.041 \({}^{\star}\)** & & \\ Age & \(-0.38\) & \(-0.77\) & 0.02 & 0.20 & 0.060 & & \\ Sex & \(-6.15\) & \(-16.16\) & 3.87 & 5.01 & 0.224 & & \\ \hline \hline \end{tabular} B: unstandardized regression coefficient; CI: confidence interval; LL: lower limit; UL: upper limit; SE B: standard error of the coefficient; R\({}^{2}\): coefficient of determination; AR\({}^{2}\): adjusted R\({}^{2}\). \({}^{\star}\)\(p\)-value \(<0.05\)  
\end{table} 
Table 4: Linear regression results for Barthel index at baseline (BI T0).