# Bioelectrical Impedance Vector Analysis (BIVA) and Somatotype in Female Rugby Players
## 2 Materials and Methods  
A cross-sectional observational study was carried out on a sample of 19 women from a rugby team of the sub-elite Spanish National Rugby League. Athletes were studied as a total sample and classified by the player's position: forwards (\(n=8\)) and backs (\(n=11\)). The study was conducted according to the guidelines of the Declaration of Helsinki. Written informed consent was obtained from all volunteers that participated in the study. Approval was acquired from the Clinical Research Ethics Committee (CEIC) of Valladolid-East Health Area (protocol code: PI 16-512). Anthropometric measurements were taken according to standard procedures of the International Society for the Advancement of Kianthropometry (ISAK) [27]. An electronic scale and a stadiometer SEGA (Hamburg, Germany) were used for body mass (kg; precision: 100 g) and height measurements (m; precision: 0.1 cm). Body circumferences were determined with a flexible and non-extendible steel tape (to the nearest 1 cm). Skinfolds thicknesses (tricipital, bicipital, abdominal, suprailiac, subscapular, supraspinale, front thigh, and calf) were measured using a Holtain (Crymmych, UK) skinkold calliper (precision: 0.2 mm). Somatotype was calculated by the Heath-Carter method [12]. BMI was calculated and it was catalogued applying the cut-off points of the WHO [28]. Based on the Spanish Sports Medicine (Federacion Espanola de Medicina del Deporte) guidelines [9], the equations applied to estimate BC components were (1) fat mass percentage (FM%) using the Yuhasz and Carter model [29], (2) bone mass (kg) using the [PERSON] model [30], (3) residual mass (kg) using the [PERSON] model [31], and (4) skeletal muscle mass (SMM, kg) using the [PERSON] model [32]. Reference values for national sport populations were used to analyse anthropometric and BC results [33]. Whole body BIA was conducted in the mono-frequency mode (at 50 kHz, 400 \(\upmu\)ARMS) using a tetrapolar electrode configuration, with a BIA 101 AKERN-Srl bioimpedance measuring device (Florence, Italy). Measurement errors of the system, determined with a precision resistor and capacitor, were <1% for R and <2% for capacitance. R and Xc were measured using a standard protocol [34] and specific procedures for athletes [24]. FFM (kg) was estimated using the BIA equation developed by [PERSON] et al. for athletes [35]. Fat mass (FM, kg) was calculated as the difference between body mass and FFM. SMM (kg) was calculated by [PERSON] et al. 's formula [36]. For the classic BIVA, the components of the impedance vector (R and Xc) were standardised by the heights of the subjects (R/H (ohm/m) and Xc/H (ohm/m), respectively) and were represented on an R-Xc graph (abscissa axis: R/H; ordinate axis: Xc/H). The PA (degrees) was calculated as arc tangent (Xc/R). Individual impedance vectors were compared with the vector distribution from [PERSON] et al. 's reference sports population (tolerance ellipses at 50%, 75%, and 95%) [37]. For the BIVA-sp approach, R and Xc were corrected by multiplying by A/L (Rsp and Xcsp), where A is the cross-sectional area (m\({}^{2}\)) estimated as 0.45 upper arm area + 0.10 waist area + 0.45 calf area, and L is the height multiplied by 1.1 (m). The segment areas were calculated as C\({}^{2}\)/4\(\pi\), where C (m) is the circumference of the upper arm, waist, or calf. The length of the vector (Zsp) was calculated as (Rsp\({}^{2}\) + Xcsp\({}^{2}\))\({}^{0.5}\). Specific values were rescaled by a factor of 100 [20]. Individual specific impedance vectors were compared with the vector distribution from the reference sports population (tolerance ellipses at 50%, 75%, and 95%) [38]. Finally, to compare the subgroups, the 95% confidence ellipses for mean vectors of the groups (classic and specific BIVA) were drawn. Variables were described as means (SD) or medians (25 th-75 th percentiles). The normality of the distribution of the variables was checked by the Kolmogorov-Smirnov or the Shapiro-Wilk tests. Either Student t or Mann-Whitney U tests were used for pairwise comparisons.