# Bioelectrical Impedance Vector Analysis (BIVA) and Somatotype in Female Rugby Players
## 1 Introduction  
Rugby is a field-based team sport that requires qualities such as endurance, speed, agility, power, and flexibility [1, 2, 3]. Similar to other team sports, some of a player's abilities will predominate depending on their position in the field. Thus, in rugby players, it is essential to establish their positions as accurately as possible and design training strategies to optimise a player's competitive performance. Currently, body composition (BC) is considered a determinant of athletic performance [4]. Therefore, a BC assessment, in addition to anthropometric characteristics and somatotype, helps to (1) select the athlete, (2) determine their playing position, and (3) optimise both the personal and team performance [1, 2, 3]. Over the last few years, the number of studies on athletes' anthropometric characteristics, BC, and somatotype has increased. Moreover, specific profiles have been proposed as reference models for many sports [5]. However, there are few studies focused on rugby, especially female rugby. Body composition can be determined at different levels and by applying various models and methods [6]. Firstly, an assessment settling a level and a model is recommended,and then one can estimate each body component by using the corresponding reference technique [7; 8]. Reference techniques are expensive, require a qualified technician, present potential side effects, and are not suitable for use in \"on-site work\". Thus, daily sport practice requires simple, fast, inexpensive, non-invasive, and accurate methods for the study of BC. The most widely used method for BC assessment in sport is anthropometry [9]. Although this technique is commonly accepted in sports, it has low precision and requires a certain measurement time and a well-trained anthropometrist. Moreover, it does not detect changes in both BC and the hydration state on a short-term basis (before and after competition, during a sport season, etc.) [10]. It has been demonstrated that using specific predictive equations for athletes increases the accuracy of this method [11]. Additionally, this technique allows the identification of the athlete's morphological conformation using the somatotype calculated by the Heath-Carter method [12]. Bioelectrical impedance analysis (BIA) is a fast, safe, accurate, and non-invasive indirect technique for estimating BC, and its use is increasing in both clinical and sport practice. This method determines the opposition of a tissue to an alternating current with very low intensity and a specific frequency [13]. Single-frequency BIA (SF-BIA) or conventional BIA at 50 kHz is the most used modality of BIA for BC assessment. It presupposes (1) a two-compartment model of BC; (2) non-hydration alterations [14; 15; 16]; and (3) as in anthropometry, the use of predictive equations is required to quantify body volumes (fat free mass (FFM) and total body water (TBW)). These predictive models should be developed in a similar population to the studied one (in terms of sex, age, race, physiological situation, pathology, etc.). Nowadays, the study of raw electrical values of BIA at 50 kHz, such as the bioelectrical impedance vector analysis (BIVA) [17] and phase angle (PA) (quantified as the arctangent of reactance (Xc)/resistance (R)), has been encouraged to avoid a dependency on mathematical models to quantify body volumes [15; 18]. The BIVA (classic BIVA) is a semiquantitative analysis method that also allows the determination of changes in body fluids, hydration status, and body cell mass. It is based on the analysis of the impedance vectors, normalised to standing height (R/H and Xc/H). These vectors are represented in an RXc graph (in terms of age, race, and sex), which is made up of three concentric ellipses corresponding to the 50 th, 75 th, and 95 th percentiles of the normal distribution of the values of the reference population (tolerance ellipses) [19].