## 4 Discussion  
The results of this study revealed statistically significant differences in anthropometric measurements according to the position played and sex of competitive rugby players. Thus, forwards were taller, heavier and fatter than backs. In addition, forwards presented higher values for tricipital, subscapular, iliac crest, abdominal, front thigh and medial calf skinfolds and sum of six skinfolds. By sex, our results indicated lower values for height and weight in female competitive rugby players. As regards body composition assessed by anthropometry, we observed higher values for body fat and all skinfolds (except subscapular), whereas no differences in body composition were detected by BIA. Our results are in accordance with other studies that have reported a greater height and body weight in forwards compared to backs in competitive rugby players from New Zealand [33; 34], Australia [8] and Portugal [35], and in participants in the World Cup [36]. Having a higher weight correlates strongly with scrummaging force [12], a specific quality for forwards [37; 38]. Nevertheless, a higher body weight could also diminish sprint ability and endurance performance if there is increased body fat mass. In this study, we found that increased weight in male and female forwards was accompanied by increased body fat and skinfold thickness, confirming the results of previous studies on male competitive  
Figure 5: Bland-Altman graph of the muscle mass percentage in men. rugby players [8; 34; 39], and now confirming the same relationship in female competitive rugby players. This characteristic body composition (heavier and fatter) in forwards could enhance scrummaging force [12] and endow advantages when competing for the ball in scrums, trucks and mauils by attenuating the transfer of forces and reducing risk of injury [6; 10]. Nevertheless, the % body fat of male rugby players in this study was higher than that reported in competitive rugby players from countries that have obtained better results than Spain in international championships, such as New Zealand [33] and Australia [8]. Thus, this higher body mass that includes a higher fat mass in the Spanish players who participated in this study does not seem to provide additional benefits for specific abilities in rugby and could diminish tackling [23], acceleration and sprint [2] abilities. In contrast, the female rugby players in this study had less fat than South African competitive rugby players [40]. This lower body fat level might imply faster, higher acceleration in backs in Spanish competitive rugby, but could also result in a worse specific action that may contribute to Spain's moderate level of achievement in rugby. Regarding the sum of six skinfolds in Spanish elite rugby players, the mean in men was 75 mm in backs and 110 mm in forwards. In women, the mean was 60 mm in backs and 90 mm in forwards [41], and the average sum of six skinfolds was different in each sex. This finding has also been reported in other studies [33; 42]. The lower level of body fat and higher lean body mass in male backs compared with forwards reported in this study are consistent with results previously reported for Australian [8], Argentinian [7], Italian [10] and Spanish [41] competitive rugby players. This body composition endows backs with the potential to improve tackling ability [23], acceleration and speed, and enhances thermoregulation [2; 11], enabling them to cover a greater distance [5], increase acceleration during dynamic phases of the match and improve their role on the field [6; 40; 43]. One of the novelties of this study has been to confirm that these differences between positions observed previously in competitive male rugby players [7; 8; 10] and in the male participants in this study are also evidenced in female competitive rugby players.