###### Abstract  
The majority of BIA parameters have been investigated in relation to post-stroke recovery, except for body cell mass (BCM), which measures the body's cellular components involved in oxygen consumption and nutritional status. The aim of this longitudinal prospective study was to investigate in a cohort of subacute post-stroke patients undergoing rehabilitation the body composition parameters from BIA and the relationship between these parameters, in particular BCM, with both the performance in activity of daily living (ADL), measured by Barthel's Index at admission (BI T0), and the recovery in ADL, measured by change in BI from baseline (\(\Delta\)BI). We analyzed 66 patients, before and after a six-week rehabilitation program and we found that patients' body composition after the rehabilitation protocol did not change. All lean mass and muscle quality parameters measured by BIA are positively correlated with BI T0. Moreover, patients with better recovery had higher values of BCM, such as other lean mass parameters and their related height-adjusted indices. Furthermore, BCM was independently associated both with ADL performance at admission, and most notably with recovery. These results suggest that assessing BCM at admission not only would improve the valuation of the nutritional status in post-stroke patients but would also potentially predict their recovery. bioelectrical impedance analysis; BIA; body cell mass; body composition; post-stroke; rehabilitation; fat-free mass; muscle mass; muscle quality; phase angle +
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In fact, neurological disorders, inflammation, and immobility related to stroke could lead to progressive muscle atrophy [12; 16]. This condition, known as \"stroke-related sarcopenia\", could contribute to worse recovery after rehabilitation [17; 18; 19], whereas an improvement corresponds to a better functional outcome [20]. There are several methods to assess body composition: among them, computed tomography (CT) and dual-energy X-ray absorptiometry (DEXA) are considered the gold standard. However, these devices are expensive, are not transportable, and need highly qualified personnel for the analysis, and they also expose patients to ionizing radiation of diverse intensities [21]. On the other hand, bioelectrical impedance analysis (BIA) is commonly used to analyze body mass compartments due to its low cost, simplicity, safety, and non-invasiveness. BIA measures the electrical properties of the tissues and indirectly evaluates the body composition compartments [22]. Different body composition parameters can then be estimated by means of predictive equations including BIA variables, sex, age, stature, and weight. Recently, there has been a rapid increase of studies on body composition in terms of the BIA parameters in relation to functional and clinical outcomes after stroke [17; 23; 24; 25; 26; 27; 28; 29; 30]. In particular, muscle mass and muscle quality parameters have been shown to be associated with functional independence measure at discharge [24; 30], modified ranking score at discharge [17], and the Fugl-Meyer of upper limb at discharge [25]. In addition, the results of a recent retrospective multiple linear regression analysis demonstrated that the phase angle (Pha) and muscle mass were independently associated with better recovery after acute stroke [27]. Moreover, the skeletal muscle index (SMI) estimated with BIA together with muscle-strength assessment is employed for sarcopenia diagnosis according to the revised European Consensus, from the European Working Group of Sarcoma in Older People 2 (EWGSOP2) [31]. In this context, the study of body composition appears essential to better characterize the general health status of patients admitted to a rehabilitation unit after a stroke injury. Noteworthy, some BIA-derived parameters were not sufficiently explored in post-stroke patients, especially in relationship to recovery outcome after a rehabilitation treatment.