Global positioning system tracking and kinanthropometrical profiling of Zimbabwean National Rugby Sevens players

Abstract

Rugby sevens has continuously increased in popularity around the world, receiving Olympic status in 2009 to be included as an event at the 2016 Olympic Games. This status will probably motivate international teams participating in this event to pursue performance even more in their quest to win an Olympic medal. Coaches, sport scientists and selectors are known for placing strong emphasis on certain physiological characteristics of rugby players such as distance covered, speed and work rate, as well as certain morphological characteristics when recruiting, selecting and training rugby players. However, significantly less scientific research studies have been done on the physiological and morphological characteristics of rugby sevens compared to studies done on rugby union. The scarcity of scientific research on rugby sevens is difficult to understand when the evidential status and popularity of this sport code is considered. The following three objectives of the study were achieved through an ex post facto research design. Firstly, a comparison of the different player position subgroups of elite, national, rugby sevens players with regard to time-motion analyses and kinanthropometric profiles was done. This was followed by an examination of the physiological demands rugby sevens places on its players with regard to different levels of tournaments. Finally, the effect of fatigue on the percentage of time sevens rugby players spend on the movement activities during the two different halves of match-play and the percentage time starter and substitute players spend on high and low-intensity movement activities were compared. Players were clustered into two positional subgroups, namely forward and backline players. One hundred and eleven sets of time-motion analysis data of elite male, senior, Zimbabwean national rugby sevens players with a mean age of 27.2 years were gathered. Time-motion analysis data sets were acquired by means of a GPS device at 10 Hz (Catapult Innovation, Melbourne, Australia) during match play. Kinanthropometry data such as stature, body mass, skinfolds, girths and breadths were measured following the standard procedures as described by the International Standard for the Advancement of Kinanthropometry. Body mass and stature were then used to calculate the Body Mass Index, and the different somatotypes were calculated to the nearest 0.1. Kinanthropometric results indicated that an average Zimbabwean rugby sevens player is 178.4 cm tall and has a body mass of 84.2 kg. The forward players had a practically significantly higher body mass and stature than the backline players. The backline players also differed from the forward players with significantly less muscle mass and percentage muscle mass respectively. Forward players revealed a practically significantly larger forearm girth value compared to that of backline players, as well as a practically significantly bigger femur breadth value. The forward players had a practically significantly higher mesomorphy value compared to the backline players. However, both positional subgroups tend to be dominant mesomorphic in nature with the average somatotype for the total group as endomorphic mesomorph. The kinanthropometry data highlighted that rugby sevens requires players with different types of body composition to adhere to the responsibilities set for the different player position subgroups despite the players exhibiting homogenous somatotype and BMI values. Time-motion analysis suggested that the elite rugby sevens players travelled an average distance of 1 073 meters (m) at an average work-to-rest ratio of 1:4.7. Forward players spent a moderate, practically significant percentage of time more on walking and less on sprinting than backline players. The work-to-rest ratio of the players indicated that the backline players had moderately practically significantly less rest during a match than forward players. Again, rugby sevens players seem to requires different playing positions to adhere to different responsibilities set for the respective player position. Rugby sevens players spend a practically significant percentage more time standing during international tournaments than during national and district tournaments. The players also spend a practically significant percentage less time on high intensity running during international tournaments than during national and district tournaments. The only practically significant difference (moderate) found between the national and district tournaments were the larger percentage of time players jogged during the district tournament. Finally, players exhibited work-to-rest ratios during international matches inferior to the work-to-rest ratios exhibited during district and national tournaments. Stronger opponents at international tournaments, crowd support and travel fatigue during international tournaments may explain the time-motion analyses differences found. Rugby sevens players travel an average of 548.1 meters a half and a significantly further distance in the second half compared to distance travelled in the first half. Players spend a moderately practically significant percentage less time on standing in the second half than in the first half. The players did, however, spend a significantly percentage time more on slow jogging and medium-intensity running in the second half than during the first half. No practically significant differences were found between the percentage of time players had spent on high-intensity running and sprinting between the two halves of rugby sevens match play suggesting that fatigue did not affect the players' movement activities. Starter players covered a significantly greater distance than substitute players, but substitute players covered a significantly greater relative distance than the starter players. The starter players had spent significantly percentage more time walking than substitute players and the starter players recorded significantly lower work-to-rest ratios than the substitute players. The results therefore suggest that the use of substitute players may support the ability of teams to increase the percentage of time the players spend on high-intensity activities. To the knowledge of the current research team, no literature could be found that offers such a comprehensive positional kinanthropometric profile of national rugby sevens players. Furthermore, this is the first study that compared the time-motion analyses data between the player positional subgroups and the movement activities of three different levels of rugby sevens tournaments.