# Bioelectrical Impedance Vector Analysis (BIVA) and Somatotype in Female Rugby Players
## 4 Discussion
That is why in BIVA-sp, a correction in R and Xc values for cross-sectional areas is made in order to reduce the differences related to size and body shape. This modality is more sensitive to the bioelectrical properties of the tissues and evaluates BC in a more reliable way [20]. In fact, BIVA-sp showed, in a statistically significant way, the BC differences between forwards and backs (Figure 4b). In forward players, as other authors have documented, the length of mean impedance vectors is higher than in backs, which indicates a higher FM% [21; 54; 56]. Most of the players presented a similar specific individual impedance vector distribution in the tolerance ellipses of BIVA-sp (Figure 3) compared to the reference values in sports populations. The vectors of five players were allocated out of the ellipses at 75%, within the left upper quadrant (players number 7, 10, 13, 18, and 19). These players (all forwards) registered the highest values for BMI and FM%; therefore, their position in the BIVA-sp graph agrees with other studies [57]. However, player number 9, who is placed in the right upper quadrant in the BIVA graph, is in the centre of the ellipse in the BIVA-sp graph, which shows the normality of her BC. Additionally, there is a player out of the ellipse at 75% within the right lower quadrant, with a reduced length of the Zsp vector (subject 12). She is a back player with a BMI of 18.0 kg/m\({}^{2}\) and a low FM. Finally, the back player (number 15) was situated out of ellipse at 75%, in the left at the limit of upper and lower quadrants. Shepresented a BMI of 21.5 kg/m\({}^{2}\) with a moderate FM and a high SMM, as indicated by PA, and was the highest of the team (great body cell mass and lower ECW/ICW relationship, due to the higher ICW). The somatotype analysis corroborates many of these BC characteristics. As an example, Figure 1b shows that player number 12 is the only one with an ectomorphic somatotype. Players with a high body mass and FM% are allocated in the mesomorph endomorph axis, but out of the somatochart (the values of players number 13 and 19 were so extreme for X and Y that they cannot be drawn on the somatochart). Little research has been conducted to analyse impedance vector distribution according to athlete somatotype [26; 53; 58; 59]. Statistically significant correlations between impedance vector and PA and some components of somatotype have been found; however, the studied samples were reduced (only from sports such as soccer) and mainly in male athletes [26; 53; 58; 59]. This study presents some limitations. On one hand, there was a reduced sample size; the subjects studied were only the players from a sub-elite rugby team who voluntarily wanted to participate, but it was a small team. Ideally, the sample size would be increased by including players from rugby and other sports, individual and team sports, and with sub-elite and elite athletes. Additionally, on the other hand, the obtained results can only be extrapolated to other research works that use similar BIA devices at 50 kHz with the same protocol and in similar populations. In sports, where fast, accurate, and simple measurements are required, the application of BIVA, in both classic and specific modalities, can be a very helpful strategy for BC analysis [60]. Both conventional BIA and BIVA techniques do not present anthropometry limitations such as errors derived from predictive models, a high inter- and intra-observer variability, and a specific measurement time. Classic BIVA could be useful to evaluate hydration variations, while BIVA-sp could be employed to monitor changes in FM% during seasons or according to different training strategies in order to improve BC and competitive performance. Given the particularities of this sport and the physiological characteristics of women, this could be particularly important in rugby female players. Moreover, the use of BIVA to assess BC in semi-professional teams would assist in improving the physical condition and performance of the players.