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The purpose of this study was to investigate longitudinal body composition of professional rugby 2 union players over one competitive season. Given the potential for variability in changes, and as the 3 first to do so, we conducted individual analysis in addition to analysis of group means. Thirty-five 4 professional rugby union players from one English Premiership team (forwards: n=20, age: 25.5±4.7 5 years; backs: n=15, age: 26.1±4.5 years) received one total-body dual-energy X-ray absorptiometry 6 (DXA) scan at preseason (August), midseason (January) and endseason (May), enabling 7 quantification of body mass, total and regional fat mass, lean mass, percentage tissue fat mass 8 (%TFM) and bone mineral content (BMC). Individual analysis was conducted by applying least 9 significant change (LSC), derived from our previously published precision data and in accordance 10 with International Society for Clinical Densitometry (ISCD) guidelines. Mean body mass remained 11 stable throughout the season (p>0.05), but total fat mass and %TFM increased from pre to endseason, 12 and mid to endseason (p<0.05). There were also statistically significant increases in total-body BMC 13 across the season (p<0.05). In both groups, there was a loss of lean mass between mid and endseason 14

Body composition analysis using dual-energy X-ray absorptiometry (DXA) is becoming increasingly popular in both clinical and sports science settings. Obesity, characterized by high fat mass (FM), is associated with larger precision errors; however, precision error for athletic groups with high levels of lean mass (LM) are unclear. Total (TB) and regional (limbs and trunk) body composition were determined from 2 consecutive total body scans (GE Lunar iDXA) with re-positioning in 45 elite male rugby league players (age: 21.8 ± 5.4 yr; body mass index: 27.8 ± 2.5 kg m(-1)). The root mean squared standard deviation (percentage co-efficient of variation) were TB bone mineral content: 24g (1.7%), TB LM: 321 g (1.6%), and TB FM: 280 g (2.3%). Regional precision values were superior for measurements of bone mineral content: 4.7-16.3 g (1.7-2.1%) and LM: 137-402 g (2.0-2.4%), than for FM: 63-299 g (3.1-4.1%). Precision error of DXA body composition measurements in elite male rugby players is higher than those reported elsewhere for normal adult populations and similar to those reported in those who are obese. It is advised that caution is applied when interpreting longitudinal DXA-derived body composition measurements in male rugby players and population-specific least significant change should be adopted.

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The use of global positioning systems (GPS) technology within referees of any sport is limited. Therefore, the purpose of the current study was to evaluate the movement and physiological demands of professional rugby league referees using GPS tracking analysis. Time-motion analysis was undertaken on 8 referees using 5-Hz GPS devices and heart rate monitors throughout a series of Super League matches. 44 data sets were obtained with results identifying similar total distance covered between first and second half periods with a significant (P=0.004) reduction in the number of high velocity efforts performed between 5.51?7.0?m.s?1 (1st=21?8, 2nd=18?8). Mean distance covered from greatest to least distance, was 3?717?432?m, 3?009?402?m, 1?411?231?m, 395?133?m and 120?97?m for the following 5 absolute velocity classifications, respectively; 0.51?2.0?m.s?1; 2.1?4.0?m.s?1: 4.01?5.5?m.s?1; 5.51?7.0?m.s?1; <7.01?m.s?1. Heart rate was significantly (P<0.001) greater in the first (85.5?3.4% maxHR) compared to the second (82.9?3.8% maxHR) half. This highlights the intermittent nature of rugby league refereeing, consisting of low velocity activity interspersed with high velocity efforts and frequent changes of velocity. Training should incorporate interval training interspersing high velocity efforts of varying distances with low velocity activity while trying to achieve average heart rates of ~?84% maxHR to replicate the physiological demands.