The science of hydration and refuelling for cricket

How much do cricket players sweat?

Scientists with the Australian Cricket team, Gatorade Sports Science Institute and the Australian Institute of Sport undertook tests on the Australian squad during a 2.5 hour training session (warm-up and drills, followed by bowling and batting practice in nets). The weather during the morning training session was hot, averaging 29°C and 50% humidity. Players had access to “drink stations”, with eskies of cold Gatorade and bottled water provided on the cricket ground, and near to the cricket nets. The specific gravity of urine samples (USG) collected immediately after waking up that morning showed that 5 of the 12 players were dehydrated from their previous day’s activities.  The following table summarises the estimated losses of fluid and sodium during the session for the 11 players who undertook the full training session (the results of one player who was injured were omitted). 

n=11 players	Sweat loss (ml)	Sweat loss (ml/h)	Fluid intake (ml)	Fluid intake (ml/h)	Change in body weight (% BW)	Sweat sodium concentration (mg/l)	Total sodium loss (mg)
Mean	3004	1202	2172	869	1% loss	763	2255
Range	913-4429	364-1772	1413-3034	565-1214	2% loss to 4% gain	434-1073	963-4260

The average figures suggest that the cricketers generally looked after themselves well. They made use of the available fluids to drink at a rate that replaced ~ 72% of their sweat losses.  On average, the players sweated at a rate of 1200 ml/hour, which is similar to findings from other team sports.  At the individual level, there was a different story due to the large range in results. There was a four-fold difference in the rates of sweat loss between players.  Fluid intakes also varied, although there was a trend for the “bigger sweaters” to drink more fluid during the session. Four players incurred a weight loss of more than 1.5% BW over the session.  One player gained a small amount of weight over the session, by drinking at a rate slightly higher than his sweat losses.  This player had shown a morning urinary sample consistent with dehydration, and had a lower rate of sweat loss during the session.  Replacing a little more than his sweat losses was useful in allowing him to “make up some ground” in removing his fluid deficit.  This is not to be confused with the problem of substantial over-drinking that has been reported among the slower competitors in marathons and ultra-endurance events. In these situations, athletes expose themselves to the risk of hyponatremia (low blood sodium levels) by drinking several litres of fluid in excess of their sweat rates and showing a substantial weight gain over the exercise session.
The only published study of fluid losses during cricket play found that fast bowlers were unable to main good hydration by drinking during the formal breaks in cricket on a hot day. In fact, after two sessions of play (2 x 2 hr), players had lost an average of 4.3% of body weight (BW). Generally, athletes are advised to follow hydration strategies that keep their fluid losses to less than 2% BW (Gore et al. 1993).

How does hydration and refueling affect cricket?

A study of sub-elite cricket players found that a fluid deficit of just under 3% of body weight impaired their ability to undertake a shuttle run in moderate weather conditions. The fluid deficit was also associated with a reduction in the line and length of accuracy of bowling by ~15%, although bowling speed was not affected.  In contrast, bowling skills and endurance were maintained when players drank sufficient fluid over the session to keep the deficit to ~ 1% of body weight. The negative effects of a fluid deficit on performance are generally higher when exercising in hot conditions. (Devlin et al. 2001). 

Fluid Guidelines for Cricket Players

Monitoring hydration status

Monitoring body weight changes over a selection of training and match scenarios will provide a quick check of how well your fluid practices track your sweat losses in a variety of exercise scenarios.  You should weigh yourself in minimal clothing before the session. After the session, you should towel yourself dry and weigh again in the same clothes. It is assumed that the difference in weight is predominantly due to changes in fluid balance.  If you are also able to keep track of how much you drink and eat (in grams) during the session, and any weight changes due to toilet stops during the session, this will allow you to estimate your total sweat losses:

Sweat loss (ml)  = weight change over the session (g) + weight of fluid/food consumed (g) – weight change due to a toilet stop (g)

Information collected first thing in the morning can provide a cricketer with an indication of day-to-day hydration practices, and specific hydration status on the morning of a training session or match. It is useful to track morning body weight from day to day, by weighing yourself after waking up and going to the toilet.  A sudden loss of > 0.5 kg may indicate a fluid deficit from the previous day(s) fluid intake practices.  Of course, other conditions that affect body weight need to be taken into account (clothing, using the same set of reliable scales, emptying bladder/bowel on waking, sudden reduction in food intake, or a general weight loss program).  When these factors are kept constant, a sudden substantial change in weight usually indicates a fluid deficit.
Some cricket players have access to monitoring the characteristics of their first urine sample of the day – for example, the Specific Gravity of their urine (USG). A morning USG reading > 1.020 confirms other evidence of a fluid deficit and suggests that fluid practices of the previous day(s) have fallen behind fluid needs.

Competition drinking strategies for players

• Sweat rates and fluid needs vary according to your role in the team (e.g. batting, bowling), your playing style and the weather.  You should have a fluid intake plan based on your individual needs, rather than a “one size fits all” approach for all players in the team.  The general advice for fluid intake during exercise is to try to drink to replace most of your sweat losses, at least to the level that is practical and comfortable.  Typically, athletes are advised to try to keep fluid deficits to less than 2% of body weight.
• Warm-up, drinks and meal breaks provide good opportunities to drink fluid during a match, but in most situations, you will be unable to achieve adequate hydration by relying only on these opportunities alone.
• When sweat losses are high, you should take advantage of the opportunity to drink from the side-line during over changes and the fall of wickets. Of course, you can also drink when your team is batting, and you are not on the field.  It is usually not possible to drink at a rate that replaces all sweat losses incurred during the game; however you should drink at a rate that is comfortable and keeps pace with sweat losses as well as possible.
• Be wary of drinking at a rate that exceeds your sweat losses, so that you gain body mass over a match.  It may be useful if it helps you to turn around a fluid deficit that you carried into the session. However, over-consumption of fluids can lead to gastrointestinal discomfort.  If carried out to extremes, it can also cause a medical problem called hyponatremia, where blood sodium concentrations fall to a dangerous level.
• Having your own drink bottles avoids the hygiene problems associated with sharing drinking vessels. It also allows you to keep track of how much you have consumed over the match.
• Sports drinks provide opportunities for intake of fuel as well as fluid during training, and during matches when fielding or batting  Research shows that carbohydrate intake may enhance performance during matches by increasing endurance and delaying the onset of fatigue.  In comparison to water, sports drinks may help you to perform for longer and at a higher intensity for the duration of the match, and to maintain skills and decision-making capability at an optimum level. Sports drinks would not be necessary for the remainder of the batting team during a match as they have access to food in the change rooms.

Training drinking strategies for players

• Training sessions often provide the most practical opportunity to undertake monitoring of your typical sweat losses in different cricket activities.  Monitoring changes in body weight over the session, adjusted for toilet breaks and intake of food and drinks, can provide a picture of your sweat losses, success in replacing fluid during the session and the remaining fluid deficit at the end of the session.  This information can help you to develop a fluid intake plan for training and matches, and to monitor the results from time to time.
• Make use of scheduled breaks in team and individual training sessions to achieve your fluid intake plan.
• Take a drink bottle and have a fluid intake plan for all training sessions, regardless of the weather or perceived need to drink.  Even in cool weather or an indoor environment, it is possible that sweat losses can be substantial.
• Sports drinks provide opportunities for intake of fuel as well as fluid during training.  This may help to sustain skills and work output right to the end of lengthy sessions.
• Be wary of drinking at a rate that exceeds your sweat losses, so that you gain body mass over the training session.  It may be useful if it helps you to turn around a fluid deficit that you carried into the session. However, over-consumption of fluids can lead to gastrointestinal discomfort.  If carried out to extremes, it can also cause a medical problem called hyponatremia, where blood sodium concentrations fall to a dangerous level.
• When you are training more than once in a day, you will need a careful fluid intake plan for each session, and for full rehydration between sessions.

Issues for team management/coaches

• A professional approach is to have a “team drinking plan” that incorporates the range in needs of all players, rather than relying on “good luck” practices of individual players or “one size fits all” for the team.
• It is good to encourage individual or team “fluid monitoring” activities. Monitoring changes in body weight and fluid intake over training sessions and matches will provide each player with a feel for their typical sweat losses in different situations.  It will also provide each player with some feedback of how well their present practices meet their needs.  Players who continually fail to hydrate appropriately during training or matches should be referred for specific advice.
• There should be an adequate supply of fluids available to players, especially when matches are played at a remote location away from a water supply, or in countries where the local water supply is unsuitable for consumption.  Calculations should be made to supply a volume of fluid that is adequate to cover the needs of each player.
• Best practice is to provide team supplies of sports drink and water in insulated drink coolers.  This ensures that players have access to suitable and palatable drinks, but also provides an education message that hydration practices are important.
• Provision of separate drink bottles to each player provides further opportunity and education regarding fluid intake during the match.
• Issues of drink availability (provision of coolers and bottles) are also important in the training situation.  The coach should schedule regular drink breaks in the training program according to the likely fluid needs of the players.  This may need to be adjusted according to the weather and the intensity of training. Players should receive encouragement and education messages about suitable hydration practices during training sessions at each break.

References
Devlin L.H., Fraser, S. F., Barras, M. S. and Hawley, J. A. Moderate levels of hypohydration impairs bowling accuracy but not bowling velocity in skilled cricket players. J Sci Med Sport 2001; 4: 179-187. 
Gore, C. J., Bourdon, P. C., Woolford, S. M. and Pederson, D. G. Involuntary dehydration during cricket. Int J Sports Med 1993; 14: 387-395.

Written by AIS Sports Nutrition, last updated December 2009. © Australian Sports Commission.