The Hydration Profile of Female Cricket Players During Competition

Transcription

1 International Journal of Sport Nutrition and Exercise Metabolism, 2007, 17, Human Kinetics, Inc. The Hydration Profile of Female Cricket Players During Competition Karen Soo and Geraldine Naughton This study investigated the hydration profile of high-performance female cricket players competing at a national tournament. The profile comprised hydration monitoring (n = 18) and a questionnaire (n = 20). Our objectives were to 1) advance the understanding of fluid losses in cricket sessions across a tournament and 2) assess the hydration knowledge and practices in female cricket players. Body mass before and after each game inning was recorded in order to estimate sweat rate, sweat loss, and percentage body-mass loss. Comparisons were made between groups categorized according to level of activity during each inning. When sweat rates were estimated according to actual activity time, results were in the range of those in other female team sports but less than results from male cricket players. A range of knowledge of hydration issues was also observed. This study supports the need for individualized hydration recommendations and provides direction for further hydration education in womenʼs cricket. Key Words: health behavior, sport, nutrition, sweat, dehydration Cricket, from a physiological perspective, is a prolonged, variable-intensity team sport. The level of activity ranges from short bursts of sprinting, for example, during batting, to brief periods of low-intensity activity, including standing, while fielding. Because of the unpredictable nature of the game, factors influencing hydration state have a varying emphasis compared with those in the controlled-intensity activities of endurance sports. In cricket, environmental conditions, duration of batting and fielding, and rules regulating fluid intake are some factors contributing to hydration state, in addition to level of activity. In Australia, cricket is traditionally a popular summer sport in which players might compete for up to 6 h under, at times, hot conditions and often on repeated days. In addition, cricket uniforms and protective equipment are frequently composed of materials less than appropriate for effective sweat evaporation (12). Collectively, these playing conditions increase the potential risk for significant dehydration during competition. Incurring fluid deficits during exercise, detrimental effects of dehydration, and links with hyperthermia have a strong evidence base (4, 22, 23). In addition Soo is with Sports Medicine Programs, School of Medical Sciences, University of New South Wales, Sydney, Australia. Naughton is with the School of Exercise Science, Australian Catholic University, Sydney, Australia. 14

2 Hydration in Female Cricket Players 15 to potential adverse effects on the cardiovascular system (6, 9, 16) and skeletalmuscle metabolism (13), dehydration can compromise cognitive function. A feature of cricket and other team sports might be a greater reliance on cognitive skills; in unpredictable (open-loop) games such as cricket, decision making regarding optimal ball delivery and responding to scoring opportunities are frequently required. Decrements in psychomotor tests for cognitive function were reported with body-fluid losses of greater than 2% after exercise in the heat (10). Dehydration could therefore have a potential adverse effect on tactical choices and player effectiveness in cricket. Compared with the literature on endurance sports, relatively few studies have examined fluid balance in certain team sports and, in particular, with women. Motor soccer-skill performance was observed to deteriorate when male soccer players sustained a body-mass loss during exercise without fluid replacement compared with hydrated players (15). In cricket, only 2 studies have investigated issues related to fluid balance. Both assessed male players only. Sweat rates and dehydration levels were studied during simulated and actual cricket matches (11). The second study found an impairment of bowling accuracy with exercise-induced hypohydration (7). Our twofold objectives were to advance the understanding of fluid losses in cricket sessions across a tournament and assess the hydration knowledge and practices in high-performance female cricket players. This information could then be used to enhance education efforts on specific hydration guidelines and strategies for women in cricket. Our hypotheses were that 1) the more active players would incur greater sweat losses during exercise and 2) body-mass changes observed would be comparable to those in other female team sports. Materials and Methods Participants Eighteen female cricketers competing in the Cricket Australia Womenʼs Cup held in Sydney, Australia, in December 2003 volunteered to participate in this study. This annual round-robin cricket tournament was played between Australian State second 11 womenʼs cricket teams. These players were ranked among the top 20 female players in their respective states. At the time of publication of this study, the Australian womenʼs team were the World Cup champions. The tournament consisted of a series of 1-day limited-over cricket matches originally to be played over the course of 5 days; however, competition was restricted to 4 days because of rain on the final day. The odd number of teams participating permitted a rest day during the week for each of the 5 teams. The nature, object, and possible risks involved in the study were explained to players, and informed consent was obtained. The study was approved by the Human Research Ethics Committees of the University of New South Wales and the Australian Catholic University. The study consisted of 2 components: tournament-related body-mass and urine specific-gravity measurements and a questionnaire assessing hydration knowledge and habitual practices. Players were excluded from the analysis of body mass

3 16 Soo and Naughton and urine if data collection coincided with a menstrual period (n = 2), prescribed medication affected fluid balance (n = 1), or they had a medical illness known to affect urine output, temperature regulation, or fluid balance. Measurements Urine specific gravity was determined using an optical refractometer (Uricon-NE, Atago, Japan), which was calibrated using 2 control standards before and after measurement each day (coefficient of variation 0.03%; Liquicheck, Bio-rad Laboratories Diagnostic Group, USA). Body mass was measured using digital scales accurate to 50 g (UC-321, A&D, Japan) and 100 g (Metropol, Soehnle-Waagen, Germany; and 1609N, Tanita, Japan). Players were weighed in undergarments, having towel-dried before weigh-in. Fluid intake was determined by measuring the difference in drink-bottle weight before and after fluid consumption or by determining drink weight minus cup weight, using digital food scales accurate to 0.01 g (HF-3000G, A&D, Japan). Ambient-temperature and humidity measurements were obtained from a Bureau of Meteorology weather station within 12 km of the study location. Protocol The daily research protocol was designed to minimize disruption to team routine during the tournament. Morning. On waking, each player emptied her bladder and provided a urine sample in a sterile collection container. Specific gravity of the sample was measured in order to assess morning hydration status. The specific gravity was assessed at this time of day because it would not generally be influenced by recent fluid ingestion (20). Because we did not monitor overnight fluid intake by players, however, the interpretation that these measurements were not altered by recent consumption of fluid is based on assumption rather than evidence. Body mass was then determined after the players had voided and before breakfast was consumed. During Game. We determined playersʼ body mass before and after each inning of play. Preinning mass was measured during the warm-up before the first inning and after lunch, before the second inning. If a player was batting, postexercise body mass was measured shortly after the playerʼs dismissal or at the close of the inning if they remained not out or did not bat. Water and carbohydrate-electrolyte beverages (Gatorade ), were available at scheduled drink intervals (usually every hour) or, if required, made available during unscheduled breaks in play by teammates or team support staff. The drinks schedule for each team followed usual game practices. Toilet losses, being urine and any fecal losses, were determined as the difference in body mass before and after going to the toilet. Sweat loss was estimated using the equation: Sweat loss (L) = preexercise body mass (kg) + fluid intake (L) postexercise body mass (kg) toilet loss (kg). Sweat rate was calculated by dividing the sweat loss by the testing time and expressed as liters per hour. Percentage body-mass loss was calculated as follows: Percentage body-mass loss = [(preexercise body mass postexercise body mass)/preexercise body mass] 100. The percentage body-mass loss was

4 Hydration in Female Cricket Players 17 designated as equivalent to level of (percentage) dehydration. Potential sources of error in this estimation of sweat loss, sweat rate, and percentage body-mass loss were that respiratory or metabolic water losses and fuel-mass changes were not corrected for, and urine and fecal losses could only be measured to the nearest 50 or 100 g. Postgame. Body mass was measured 2 h after the second inning as an indicator of postgame hydration recovery. Fluid intake was not recorded during the recovery period. Posttournament Questionnaire. A questionnaire assessing hydration practices, attitudes and knowledge, and factors affecting fluid intake was distributed to players. The questions were compiled with the use of a previous publication (21). Answers were required to be in a descriptive or Likert-scale format. Statistical Analysis After tests for normality, results were reported as mean ± SD. Continuous data that were deemed nonnormally distributed were log-transformed to normality before statistical analysis. Results were further analyzed to compare 2 groups of players, an active and less active group, during each inning. A process of critical appraisal involving the national coach and players determined criteria for activity grouping. The active group comprised players who scored 20 or more runs batting, bowled 5 or more overs, or played as wicketkeeper in an inning. Players in the less active group scored less than 20 runs batting or bowled less than 5 overs during the inning. To standardize performances for rest days, results were analyzed according to the number of games played. For example, players in a team with a bye on the first day of the tournament had their game-day-1 data entered after the second day of the tournament. Three games were used for analysis because only 2 participants were involved in 4 games. Morning measure of urine specific gravity and body mass were analyzed using a 1-way analysis of variance (ANOVA) with repeated measures. Comparisons between pre- and postinning body masses across game days were made with Studentʼs paired t-tests. Independent sample t-tests were used for comparison of the active and less active groups. Significance level was set at P < Statistical analysis was performed using commercially available software (SPSS for Windows, release ). Results The age of participants ranged from 16 to 38 years. Descriptive characteristics of the participants are presented in Table 1. Temperature and relative humidity for each tournament day are presented in Table 2. Hydration Status Most innings (69%) were characterized by body-mass losses, but there were some increases in body mass (28% of innings). Two players did not gain mass at any stage of the tournament, and most players (13 out of 18) increased their body mass over an inning on 1 or 2 occasions; the greatest number of times a player gained mass was in 4 innings, and this was seen in 1 player.

5 18 Soo and Naughton Table 1 Female Cricket Players Descriptive Characteristics (N = 18) Variable Mean ± SD Age (years) 22.3 ± 6.7 Height (cm) ± 4.10 Mass (kg) 67.9 ± 13.8 Body-mass index (kg/m 2 ) 23.9 ± 4.6 Table 2 Temperature and Humidity During Each Inning for Days of Tournament Competition Tournament day Inning Maximum temperature ( C) Maximum relative humidity (%) 1 1st nd st nd st nd st nd The number of visits to the bathroom ranged from 0 to 3 times per inning, with most innings characterized by players not attending the bathroom (53%) or going once (40%). Mean toilet loss, including urine and feces, was 0.27 ± 0.28 kg in the first inning and 0.05 ± 0.09 kg in the second inning of game-day 1, 0.15 ± 0.18 kg in the first inning and 0.03 ± 0.08 kg in the second inning of game-day 2, and 0.15 ± 0.21 kg for the first inning and 0.05 ± 0.11 kg for the second inning of game-day 3. Mean sweat loss, sweat rate, fluid-intake rate, and percentage dehydration (relative to preinning mass) are summarized in Table 3. One player, a batter, had sweat losses yielding > 2% dehydration on 2 occasions; a wicketkeeper also exceeded 2% dehydration on 1 occasion. Values different from Table 3 emerged when the rate of sweat loss was calculated using actual time on the field, and playing times of less than 10 min were excluded. Mean sweat rates for batters, bowlers, and fielders combined were 0.78 ± 0.65 L/h in the first inning and 0.30 ± 0.31 L/h in the second inning of game-day 1, 0.57 ± 0.69 L/h in the first inning and 0.65 ± 0.35 L/h in the second inning of game-day 2, and 1.44 ± 1.25 L/h for the first inning and 0.64 ± 0.49 L/h for the second inning of game-day 3. Sweat rates between batters, bowlers, and fielders were not statistically different (P > 0.05). Body-mass decreases were observed between preinning and postinning mass in the first inning of game-day 2 (68.19 ± kg compared with ± 13.58

6 Hydration in Female Cricket Players 19 Table 3 Mean Sweat Loss, Sweat Rate, and Percentage Body-Mass Change Compared With Pregame Mass (% Body-Mass Loss), and Fluid-Intake Rate for Each Game-Day Inning (N = 18) Game-Day 1 Game-Day 2 Game-Day 3 1st Inning 2nd Inning 1st Inning 2nd Inning 1st Inning 2nd Inning Mean sweat loss (L) 0.88 ± 0.74 ( 2.27 to 0.65) 0.52 ± 0.48 ( 1.47 to 0.36) 0.98 ± 0.65 ( 1.94 to 0.28) 0.33 ± 0.64 ( 1.76 to 0.81) 0.97 ± 0.67 ( 2.33 to 0.30) 0.93 ± 0.61 ( 2.01 to 0.13) Mean sweat rate (L/h) 0.24 ± 0.21 ( 0.62 to 0.24) 0.21 ± 0.15 ( 0.50 to 0.10) 0.27 ± 0.19 ( 0.61 to 0.07) 0.14 ± 0.46 ( 0.73 to 1.08) 0.33 ± 0.21 ( 0.64 to 0.08) 0.40 ± 0.30 ( 1.19 to 0.12) % body mass change 0.30 ± 0.85 ( 3.00 to 1.02) 0.38 ± 0.60 ( 1.47 to 0.99) 0.56 ± 0.73 ( 1.75 to 0.69) 0.11 ± 0.73 ( 0.97 to 1.36) 0.44 ± 0.82 ( 2.46 to 0.81) 0.46 ± 0.73 ( 2.19 to 0.77) Fluid intake (L/h) 0.26 ± ± ± ± ± ± 0.21 A positive value for sweat loss, sweat rate, and percentage body-mass change indicates mass gain. Range of values given in parentheses.

7 20 Soo and Naughton kg, P = 0.005) and in both innings of game-day 3 (first inning ± kg compared with ± kg, P = 0.046; second inning ± kg compared with ± kg, P = 0.018). Pre-first-inning masses and 2-h-postgame masses on game days were not statistically different (P > 0.05). No differences were observed in the morning body-mass measurements of participants across tournament days. Activity-State Comparisons Sweat rates for the active and less active groups are shown in Table 4. Differences in the percentage body-mass change between active and less active groups are shown in Figure 1. Urine Specific Gravity The mean urine specific gravity for the morning of the first day of the tournament was ± 0.006, with a range of individual values for the first day of to Urine specific-gravity values did not differ across tournament days. The lowest recorded value for the tournament was 1.009, and the highest was Questionnaire Seventeen of the 18 players (94.4%) returned the hydration-knowledge questionnaire. In addition, the 3 players excluded from the body-mass and urine results returned questionnaires. This provided a total of 20 questionnaires for analysis. Hydration Knowledge A range of opinions regarding hydration issues was observed. Ten percent of participants stated that the amount of fluid required to maintain hydration during sport was ml/h, and 65% stated that ml/h was the most appropriate amount. In addition, 25% rated hydration during cricket games as important, and 75% rated it as very important. Pregame hydration was rated important by 45% of players and very important by 55% of players. Twenty percent of players rated postgame hydration as important, and 80% rated it very important. Knowledge of the signs of dehydration during cricket was also explored. Seventy percent of players had not previously used a change in body weight to monitor their state of hydration. Hydration Practices All players consumed at least some water during training and games. Twenty-five percent of players consumed carbohydrate-electrolyte beverages in addition to water during training, and 70% stated that they consumed both during games. Self-reported amounts of fluid consumed by players during scheduled intervals are shown in Table 5. When questioned about factors that could affect fluid intake during a game, 70% of players stated that they would increase fluid intake according to the intensity of game demands sometimes or many times, and 30% stated they would always

8 Hydration in Female Cricket Players 21 Table 4 Mean Sweat Rates for the Active and Less Active Groups for Each Game-Day Inning (N = 18) Game-Day 1 Game-Day 2 Game-Day 3 1st Inning 2nd Inning 1st Inning 2nd Inning 1st Inning 2nd Inning Active mean sweat rate (L/h) 0.29 ± ± 0.12* 0.40 ± ± 0.09* 0.53 ± 0.04* 0.61 ± 0.06* Less active mean sweat rate (L/h) 0.22 ± ± ± ± ± ± 0.31 *Indicates significant difference between active and less active groups (P < 0.05).

9 22 Soo and Naughton Figure 1 Percentage body-mass change in active and less active female cricket players (N = 18). *Indicates significant difference between active and less active group in the same inning for P < Table 5 Percentage of Players Consuming Specific Amounts of Fluid at Scheduled Intervals During Cricket Matches (Self-Reported; N = 20) Amount of fluid consumed <2500 ml ml ml >750 ml Morning-session drinks interval 15% 60% 15% 10% Afternoon-session drinks interval 20% 55% 15% 10% Lunch interval 10% 30% 40% 20% increase fluids if the game intensity increased. If players were feeling ill leading up to a game, 35% of them stated that their fluid intake would mostly or always be increased. Weather conditions were perceived to influence fluid intake for all players completing the questionnaire. In assessing factors limiting fluid intake during a game, attempts to avoid abdominal discomfort were reported to alter fluid-consumption patterns by 75% of players. To avoid going to the toilet during the game, 60% of players would sometimes or always consider limiting fluid intake. The type of drink offered limited drinking intentions of only 25% of players; the type of drink was not specified. When players were questioned about whether they would request a drink while batting, in addition to scheduled drinks, if they felt it was needed, 35% replied

10 Hydration in Female Cricket Players 23 sometimes, 35% replied many times, and 30% replied always. Eighty percent of players had encountered this situation previously. When players were questioned about whether they would ask for a drink while fielding or bowling in addition to scheduled drinks, if they felt it was needed, 30% replied never, 50% replied sometimes, and 20% replied many times or always. Forty percent of players had been in this situation before. Discussion Body-mass change and urine specific gravity were used as indices of hydration state and were examined in high-performance female cricket players. A wide range of fluid losses was observed, and some players demonstrated body-mass gains. Endurance-exercise performance might be compromised when dehydration levels exceed a certain threshold (for example, body-mass loss of 2%) (4, 8), but this has not been as well studied during the intermittent activity of team sports. When sweat rate was estimated based on actual activity time, sweat-rate values were in the range of those reported for other female team athletes (2) but less than in male cricketers (11). Field research, however, restricts the more precise timing of data collections possible under rigorous laboratory conditions. In our study, preinning body masses were recorded before the start of play and were used in data analyses regardless of when players became the most active in fielding or batting. For example, pre-first-inning body mass would be recorded at 9:00 AM, before warm-up, and the match commenced at 10:00 AM, but a player waiting to bat might not have commenced activity in the game until 11:00 AM. Sweat rate for the first inning of game-day 1 was calculated as 0.24 ± 0.21 L/h, but, as already presented in the Results section, when the total sweat loss was divided by actual time on the field, a value of 0.78 ± 0.65 L/h resulted. Therefore, the results are likely to underestimate the true losses incurred during actual competitive play in cricket, because they included the time of lower intensity exercise or no activity at all. Field hydration data collected in this way might be equally important for practical purposes. Information collected in this manner would be valuable to each player to ascertain individual fluid-balance responses. Results using these methods could then also be applied practically for individualized fluid-replacement regimes. We had hypothesized that fluid loss, measured in terms of sweat rate, relative body-mass loss, and absolute sweat-loss values, would be greater in the more active players. Differences in all fluid-loss parameters were greater in the more active players in the first inning of game-day 3 only. Male bowlers have recorded sweat rates as high as 1.67 kg/h (11), but we did not establish differences in sweat-loss parameters between bowlers and batters. The reasons for the general inability to find differences between active and less active players, and bowlers compared with batters, might have been associated with a small sample size and individual physiological variations in sweating, heat tolerance, or cardiorespiratory fitness, or maybe there simply were no differences. The body-mass measurements 2 h postgame were taken to assess postgame recovery. Body masses after recovery were not significantly different than pregame values. Therefore, with a minimal body-mass loss, hydration strategies employed after games might have been sufficiently effective in restoring fluid balance to

11 24 Soo and Naughton pregame levels. Fluid and food ingested during recovery remaining in the gastrointestinal tract, however, might have also contributed to observed restoration of body mass. The daily morning body-mass measurements taken after an overnight fast did not differ across tournament days. This suggests that postgame hydration and recovery techniques continued through late afternoons and evenings each day and were sufficient to recover body mass to pretournament values. Additional support for the stability of hydrated states of the female cricket players under tournament conditions was found in the stable values for urine specific gravity. Mean urine specific gravity was on the first day and demonstrated minimal changes on subsequent days. This value is considered by some to represent the upper end of a euhydrated state (1) or the lower limit of dehydration by others (18, 19, 20). The level of found in our study might reflect the mild hypohydration of the players during a standard cricket season. Some players competed in matches in the few days before the tournament, and their specific-gravity values might have represented insufficient daily fluid-balance maintenance leading up to the event. In addition, the elevated value might have reflected inadequate hydration while traveling to the tournament (in many cases from another state). A range of knowledge of appropriate hydration practices was demonstrated. Most players believed hydration during games to be very important, and approximately half of the survey participants rated pregame hydration as important. Athletes are generally advised to offset the sweat losses sustained during activity with a matching fluid-intake rate during exercise (3, 5). With the sweat rates demonstrated in our study, this would mostly be achievable. Fluid losses not replaced during activity would then have to be restored after the game to avoid compromising performance in the next match. Athletes are also encouraged to have a preexercise hydration plan to delay or avoid the detrimental effects of dehydration during exercise. Approximately ml of fluid 2 h before exercise is suggested by the ACSM to promote euhydration before competition and to allow time for regulation of fluid balance (5). Adequate pregame hydration is important in cricket because the benefits of fluid ingestion might not be realized until min after consumption (17), and the first scheduled drinks interval might not occur until 1 h of elapsed match time. Results from the hydration-knowledge and -practices survey should provide direction for further education of female cricket players on the importance of hydration for optimal sports performance. Hydration before competition, the risk of being underhydrated when ill, and factors influencing fluid intake during games were issues explored in the questionnaire and are all salient issues for future athlete and coach education. Methods of self-monitoring fluid-balance status and strategies to maximize fluid balance and minimize inconvenience can be explored. Hydration education for cricket players is important, but it should also target umpires, coaches, and, when appropriate, parents. Of interest was the number of players recalling situations in which they had perceived a need for additional fluid intake (80% while batting, 40% fielding or bowling), compared with the number who indicated that they would always actually ask for a drink if required (30% while batting, 10% fielding or bowling). One drinks interval per session of play is generally permitted in cricket matches (except in

12 Hydration in Female Cricket Players 25 1-day international matches, where 2 per session are allowed). This usually results in a drinks interval after an hour of play. International Cricket Council rules allow international games extra drinks intervals under conditions of extreme heat and permit individual players to be given a drink on the field if required (14). With better education and inclusion of additional local competition rules regarding drinks intervals, cricketers at all levels would be able to access fluid when required. This could avoid possible hydration-related compromise to skill execution. Although there has not been a case of heat stroke in cricket reported in the literature, significant sweat losses have been sustained by male bowlers under hot conditions in Australia (1.67 ± 0.08 kg/h and 4.3% dehydration) (11). There might be a potential for some individuals to be at risk for heat illness under extreme circumstances, with dehydration being one of many factors contributing. This is the first study to profile hydration practices and knowledge of highperformance female cricket players. Sweat-rate and percentage-body-mass-change results were modest because of the calculations, including time of low-level or no activity (e.g., waiting to bat, warm-up), small sample size, mild to very warm environmental conditions, and variability in activity level both between players and in the same players on different days. The study demonstrated, however, that female cricket players are capable of incurring disturbances in their fluid-balance state during competition. Self-monitoring body-mass changes at different times during match days and under different environmental conditions would allow players to more accurately assess their individual fluid requirements in a variety of situations. Increased education of players, coaches, and umpires at all levels and local competition-rule additions could minimize potential risk of hydration-related performance compromise or, on rare occasions, serious medical consequences. A reporting system for heat- and dehydration-related illnesses would help establish the incidence of such events to assist with future policy and rules planning. Acknowledgments The authors wish to thank Peter Murphy, Jennie Lane, Alex Blackwell, Rebecca Enright, Haylie Bennett, and Patrick Price for their research assistance; Belinda Clark and Stephen Jenkin from Cricket Australia for their assistance with organization of the project; Kenneth Graham from the NSW Institute of Sport for loan of equipment; Greg Cox and Helen OʼConnor for their advice in preparation of the manuscript; and the cricket players and their support staff who participated in this study. No external sources of funds were used to conduct this project. References 1. Armstrong, L.E., C.M. Maresh, J.W. Castellani, M.F. Bergeron, R.W. Kenefick, K.E. LaGasse, and D. Riebe. Urinary indices of hydration status. Int. J. Sport Nutr. 4: , Broad, E.M., L.M. Burke, G.R. Cox, P. Heeley, and M. Riley. Body weight changes and voluntary fluid intake during training and competition sessions in team sports. Int. J. Sport Nutr. 3: , Casa, D.J., P.M. Clarkson, and W.O. Roberts. American College of Sports Medicine roundtable on hydration and physical activity: consensus statements. Curr. Sports Med. Rep. 4: , 2005.

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