Journal Title (Medline/Pubmed accepted abbreviation): Appl. Physiol. Nutr. Metabol.
Page numbers: 790-796
doi (if applicable): 10.1139/H10-077
Summary of Background and Research Design
Background:Rugby is a physically demanding sport, with an estimate that players can expend 24 kcal/min. Sweating is a mechanism of heat dissipation during high intensity exercise and, if sweat loss is not balanced with fluid intake, performance can suffer.
Research Goal:To assess the hydration status of rugby league players with body mass loss (attributed to water loss), urine volume, fluid intake, and urine osmolality during the 2008 Super League season (February-August 2008).
Subjects:Fourteen professional rugby league players from 2 English Super League clubs; age 26.0 ± 4.1 from club A (n = 7) and 26.0 ± 3.3 from club B (n = 7).
Body mass, urine output, and fluid intake was measured at the beginning and the end of all of the home games. The number of observations from each player varied due to time of recruitment, but 36 observations was made from each of the 2 teams.
Two hrs prior to the game, a urine sample was acquired to assess osmolality. After the bladder void, body mass was measured. Fluid intake and excretion habits were monitored prior to the match and at half time for both teams. Fluid intake during the game was possible for club B but not club A. At the end of each match body mass and urine samples were acquired before any post-match beverages were consumed.
Summary of research findings:
On average, players lost 1.28 ± 0.7 kg during a match (1.31% of body mass). There was notable intra-individual variation between games in regard to both absolute and relative change in body mass. The mean fluid intake for club B, between arrival and post-match, was 1.56 ± 0.6 L (range 0.4 – 3.5 L). The greatest amount of fluid was consumed between arrival and kick-off. It was calculated that 67% of fluid consumed was retained overall with 84% of fluid consumed at half time being retained. Total fluid intake was not correlated with urine osmolality on arrival.
Interpretation of findings/Key practice applications:
The main highlight from this study was the large intra- and inter-individual variation in players’ hydration practices. The American College of Sports Medicine recommends players consume 0.4-0.9 L of fluid during 66 min of running; some rugby players consumed practically no fluids while some consumed up to 2.4 L. (The average fluid intake exceeded this recommendation at 1.56 L.) The large fluid intake noted before the event illustrated that players anticipated the large fluid losses. On average, players were dehydrated 1.31% after the game. Although euhydration is optimal, this amount of dehydration is less than the 2.0% that is likely to cause a reduction in performance.