Hydration status of high performance New Zealand Rugby Union players in a match context : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Nutritional Science, Massey University, Albany, Auckland, New Zealand

Abstract

The changes in body mass and urinary specific gravity of 24 rugby union players in the New Zealand Super12 development championship, were measured during five actual matches. The climatic conditions measured were ambient temperature, relative humidity and wind speed. All subjects participating in this study regardless of playing time showed a loss in body mass after each game. Fluid was available from bottles during formal breaks in play and during the ten-minute break at half time. The mean percentage of drink breaks utilised was only 48%, however this varied between games. The average change in body mass, or fluid deficit, of participants playing 60 minutes of rugby or more was calculated to be 1.87% ± 0.19% (SEM), and the range was 0.10% to 4.61%. Urine analysis for specific gravity supported the fluid deficit data, as the average urine specific gravity for players participating in 60 minutes of rugby was 1.025 and therefore considered to be dehydrated. Final hydration status is related to the length of time a player is on the field, however even reserve players showed a loss of body mass between the pre-match to the post-match weigh-in. The level of fluid deficit varied between players and for positional groups between games. However, It was observed that some players were consistently dehydrated to a high level. This indicates individual fluid ingestion strategies are required to meet the needs of each player in a team. Given the limited opportunities to replace fluid losses during rugby union, there is potential for heat stress and related illnesses to occur, however serious illness is unlikely. Dehydration can also cause impairment of both physical and mental performance, a reduced exercise capacity and impairment in temperature regulation. Rugby union players in this study were dehydrated to a level where performance may have been impaired, although future research is required to determine the level of fluid deficit at which performance impairment occurs during a rugby union match.