# Bioelectrical Impedance Vector Analysis (BIVA) and Somatotype in Female Rugby Players
## 4 Discussion  
The present study analysed the morphological characteristics and BC of a female sub-elite rugby team by two methods: anthropometry and BIA. Body mass and BC in rugby are directly related to the physical abilities of the players and their position in the field [2]. In this way, back players perform a greater amount of high speed running, involving a high heart rate, while forward players execute more medium speed running and moments with maximal demands of power and strength [40]. Given these physical demands, rugby players usually have a higher body mass and muscle mass than athletes of other sports such as soccer or hockey [2; 41]. In the present study, statistically significant differences in body mass, BMI, and FM% were found depending on each player's position; the forwards presented higher values of these variables than the backs (Tables 1 and 2). These results are similar to other studies conducted on rugby players [1; 42; 43; 44; 45]. In forward players, a higher body mass and muscle mass give them more momentum and strength when making contact, more ability to soften the impacts, and more power in scrums or rucks [1; 3]. Similarly, backs' characteristics make them faster, more agile, and with greater relative strength than forwards, which allows them to better perform their functions on the field [46]. The BC characteristics of the Spanish sub-elite rugby players studied are very similar in BMI and FM% to other elite female rugby teams from South Africa [47] and England [46; 48], despite the fact that the FM% of the Spaniards were lower. In terms of somatotype, both backs and forwards were classified as mesomorph endomorph, with the endomorphy and mesomorphy components equally dominant for each position. Endomorphy represents relative adiposity, mesomorphy represents musculoskeletal robustness, and ectomorphy represents the relative linearity of the human body [12]. Although all the studied players were classified under the same terminology, statistically significant differences were found between positions, i.e., forwards vs. backs. These results agree with other studies conducted in Spanish rugby players; forwards were represented on the somatotype chart as endo-mesomorphic [45] or meso-endomorphs [49], and backs as mesomorphic-endomorphic [45] or balanced endomorphs [49]. In the present study, agreement between anthropometry and BIA for FM estimation by using predictive equations developed in athletes was moderate (ICC = 0.626; CI 95%: 0.028-0.856). The anthropometric Yuhasz equation is widely applied to athletes and several studies have proven its reliability [9]. However, rugby players present a very different BC than other athletes, having a higher FM% and a distribution of FM not exclusively or mostly at subcutaneous level, but widespread through other parts of the body [2]. Taking into account that the Yuhasz model is based on the summatory of six skinfolds, it could not estimate accurately the BC of ruby players. Considering the BIA, the need for further development of BIA equations for athletes from different sports has become apparent [24; 35]; thus, we selected the equation of [PERSON] et al. because it is the only one specific for sports populations [35]. This predictive model was developed and validated in an athlete sample of 142 subjects (105 males and 37 females) from various individual and team sports, including rugby. [PERSON] et al. recently analysed BC in a group of both male and female rugby players [45]. This study regarded anthropometry to be better than BIA for BC estimation. However, the authors used the BC values provided by the commercial BIA device, even though this is not recommended due to the lack of information offered about the equation applied [13; 24; 50; 51]. This is possibly the reason why [PERSON] et al. demonstrated a reduced agreement due to the use of an inadequate equation for their population rather than the inaccuracy of the method [45].