The science of hydration and refuelling for basketball

How much do basketball players sweat?

Scientists with the Australian Institute of Sport and the Gatorade Sports Science Institute undertook tests on the Australian Men’s Basketball (“Boomers”) squad at a practice session during a team camp.  The squad undertook a training session of more than 2 hours (warm-up, on-court drills, and scrimmages) in an indoor stadium during winter.  The average conditions on court were 12°C and 59% humidity. Players were able to drink from individual bottles during breaks in the practice, or as they rotated between scrimmages. The specific gravity of urine samples (USG) collected immediately after waking up that morning showed that 15 of 17 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 16 players who undertook the full training session (the results of one player who was injured were omitted). 

N = 16 players	Sweat loss (ml)	Sweat loss (ml/h)	Fluid intake (ml)	Fluid intake (ml/h)	Change in body weight (% BW)
Mean	2058	895	1086	472	1.3% loss
Range	1455-2660	635-1155	490-1685	210-730	0.8% to 1.8% gain

We found a wide variability in sweat losses and fluid intakes between players. While the average fluid deficit over the session was within the general target set for athletes, two players recorded a deficit greater than 2% of their body weight.  In addition, many players carried a fluid deficit from their previous day’s training – therefore, the total level of dehydration by the end of the session may have detracted from their performance at practice.  Monitoring weight changes over the sessions can help players to see how well their hydration practices keep pace with their sweat losses.  It can be hard during a two-day practice to stay well-hydrated – even during winter.
We collected information on the fluid intake strategies of the female and male players from the Australian Institute of Sport basketball teams during several training sessions and matches, during both winter and summer.  Although there was a clear difference in the weather between seasons, the sessions were carried out in an indoor stadium that helped to reduce the differences in playing conditions. The results of our observations are summarised below.

Fluid characteristics during on-court practice – AIS males 

	WINTER (20 °C)	Sweat loss (ml)	Sweat loss (ml/h)	Fluid intake (ml)	Fluid intake (ml/h)	Change in body weight (% BW)
Mean		2145	1040	1015	490	1.2
Range		1610-2680	870-1210	590-1440	315-665	0.8 to 1.6% loss
	SUMMER (28 °C)	Sweat loss (ml)	Sweat loss (ml/h)	Fluid intake (ml)	Fluid intake (ml/h)	Change in body weight (% BW)
Mean		2300	1370	1380	795	1.0
Range		1470-3130	1135-1605	740-2020	560-1030	0.5 to 1.5% loss

Fluid characteristics during games – AIS males 

	WINTER (19 °C)	Sweat loss (ml)	Sweat loss (ml/h)	Fluid intake (ml)	Fluid intake (ml/h)	Loss of body weight (% BW)
Mean		2200	1585	1260	915	1.0
Range		1590-2810	1225-1945	635-1885	455-1375	0.4 to 1.6% loss
	SUMMER (23 °C)	Sweat loss (ml)	Sweat loss (ml/h)	Fluid intake (ml)	Fluid intake (ml/h)	Change in body weight (% BW)
Mean		2310	1600	1515	1080	0.9
Range		1710-2910	1230-1970	875-2155	465-1695	0.2 to 1.6% loss

Fluid characteristics during on-court practice – AIS females

	WINTER (17 °C)	Sweat loss (ml)	Sweat loss (ml/h)	Fluid intake (ml)	Fluid intake (ml/h)	Change in body weight (% BW)
Mean		1320	685	655	330	1.0
Range		960-1680	570-800	290-1020	175-485	0.6 to 1.4% loss
	SUMMER (26 °C)	Sweat loss (ml)	Sweat loss (ml/h)	Fluid intake (ml)	Fluid intake (ml/h)	Change in body weight (% BW)
Mean		1240	680	760	410	0.7
Range		1015-1465	540-820	450-1070	250-570	0.3 to 1.1% loss

Fluid characteristics during games – AIS females

	WINTER (17 °C)	Sweat loss (ml)	Sweat loss (ml/h)	Fluid intake (ml)	Fluid intake (ml/h)	Loss of body weight (% BW)
Mean		1320	975	810	600	0.7
Range		920-1720	720-1230	565-1055	435-765	0.2 to 1.2% loss
	SUMMER (26 °C)	Sweat loss (ml)	Sweat loss (ml/h)	Fluid intake (ml)	Fluid intake (ml/h)	Change in body weight (% BW)
Mean		1420	915	930	600	0.7
Range		1035-1805	660-1170	665-1195	430-770	0.2 to 1.2% loss

We found that sweat rates and fluid intakes of males were greater than females, reflecting their larger size. Sweat rates during games were higher than in practice, which matches the observation that time spent at high work intensities is greater during competition. Although we recommended that each player find a comfortable fluid intake plan that suits their rates of sweat loss, we noted that a typical fluid intake for junior elite basketball players during active training sessions and games might be ~ 600-1000 ml per hour.  On this basis, the coach or team manager would need to ensure that 20 litres of fluid are available on court for a 2 hour training session or match for a squad of 10-12 players (Broad et al. 1996).

How does hydration and refueling affect basketball?

Several studies involving prolonged intermittent exercise protocols or “stop-start” sports (e.g. tennis, soccer and cricket) show that dehydration and inadequate fuel cause fatigue over the course of the exercise session.  By contrast, when subjects consume fluid and carbohydrate during the session, this fatigue is reduced.  Benefits include better maintenance of activity patterns (greater distances covered at higher speeds in the later parts of a game) and better maintenance of skill and concentration.  The studies summarised below have been conducted on the specific outcomes or issues of basketball.  The duration and intensity of a single game may not be sufficiently challenging to cause nutritional fatigue in all players.  This may need to be judged for each individual.  Tournament play is likely to involve the greatest risk of nutritional fatigue since players may experience difficulty in fully rehydrating and refueling between games.  However, some studies show that players may not fully rehydrate between practice sessions during intensive training periods. Fatigue will occur earlier if fluid balance and fuel stores are not ideal at the start of a new game or practice.
Adolescent male basketball players undertook two simulated “2 on 2” full court basketball games over 40 minutes in which a series of skills and physical tests were repeated.  On one occasion players consumed water to replace their sweat losses.  In the other game, where no fluid was consumed, a fluid deficit of ~2% body weight was accumulated by the end of play.  Dehydration did not alter vertical jump height scores. However, there was a strong trend to reduced performance of a 30 second jump test (19% drop) and the accuracy of field goals (8% drop) in the dehydration trial.  These differences could affect the outcome of a real game. (Hoffman et al. 1995).
Drills and skills simulating a basketball game were undertaken over 4 x 12 min quarters on three occasions by skilled adolescent male players. On one occasion, players started the game with a fluid deficit of 2% body weight, while in other games they consumed water or a sports drink to remain in fluid balance. Shooting percentages were different between trials – 45% in the dehydration trial, 53% on the water trial and 60% with sports drink. Similarly, on-court sprinting performance was reduced by dehydration and enhanced by the addition of the carbohydrate in the sports drink. Changes in the performance of other skills and drills also showed the damaging effects of a fluid deficit and the additional benefits of consuming a sports drink compared with water (Dougherty et al. 2006).
College aged male basketball players undertook exercise in the heat on five separate occasions with various levels of fluid replacement so that they achieved a fluid deficit equal to 0, 1, 2, 3 and 4% of body weight.  Following a short recovery, they undertook a game simulation of basketball skills and drills.  The results showed that as the degree of fluid deficit increased, there was a progressive decrease in the performance of on-court sprints and shooting in comparison to the full hydration trial (Baker et al. 2006). 

Fluid Guidelines for Basketball Players

Monitoring hydration status

Monitoring body weight changes over a selection of training sessions and games 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 player with an indication of day-to-day hydration practices, and specific hydration status on the morning of a practice or game. 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 be an indication of 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 basketball 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 basketball players

• Sweat rates and fluid needs vary according to your playing style, playing conditions 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.  Monitoring body weight changes over a selection of exercise sessions will provide you with a quick check of how well your fluid practices track your sweat losses in a variety of game scenarios.
• 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, time outs, bench time and quarter/half time breaks provide opportunities to drink fluid during a game. With a good plan you should be able to use these occasions to maintain your hydration over the game. 
• In some conditions, some players will not be able 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. 
• Your fluid intake plan should not require you to drink excessive amounts of fluid, so that a substantial weight gain occurs over the game. 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 bottle avoids the hygiene problems associated with sharing drinking vessels. It also allows you to keep track of how much you have consumed over the game.
• Sports drinks provide opportunities for intake of fuel as well as fluid during games and practice.  Research shows that carbohydrate intake may enhance performance during games by increasing endurance and delaying the onset of fatigue.  It may also assist in helping to maintain concentration.  In comparison to water, sports drinks may help you to perform for longer and at higher intensity for the duration of the game, and to maintain skills and decision-making capability at an optimum level. 
• The maintenance of carbohydrate stores over the length of a tournament is also important.  Using sports drinks during a game and in recovery will assist in the maintenance of glycogen stores so that optimum energy levels are available at the finals end of the tournament.

Training strategies for basketball players

• Training sessions often provide the most practical opportunity to undertake monitoring of your typical sweat losses in different basketball activities.  Monitoring changes in body weight over a practice, 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 practice and games, and to monitor the results from time to time
• Make use of scheduled breaks in team and individual practice 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. 
• You should generally avoid drinking at a rate that exceeds your sweat losses, leading to a gain in body mass over a training session.  Of course, this might not be a problem if fluid intake helps to overturn a fluid deficit 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. 
• Sports drinks provide opportunities for intake of fuel as well as fluid during practice.  This may help to sustain skills and work output right to the end of lengthy sessions.
• When you are training more than once per 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 practice sessions and games 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 practice or games should be referred to a Sports Dietitian for specific advice.
• There should be an adequate supply of fluids available to players, especially when games 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 game.
• Issues of drink availability (provision of coolers and bottles) are also important in the training situation.  The coach should schedule regular drink breaks into the practice according to the likely fluid needs of the players.  This may need to be adjusted according to the weather and the intensity of training. At each break, players should receive encouragement and education messages about suitable hydration strategies.

References
Baker L. B., Dougherty, K. A., Chow, M. and Kenney, W. L. Progressive dehydration causes a progressive decline in basketball performance in 17-22 year old men. Med Sci Sports Exerc 2007; 39(7): 1114-1123.
Broad, E. M., Burke, L. M., Cox, G. R., Heeley, P. and Riley, M. Body weight changes and voluntary fluid intakes during training and competition sessions in team sports. Int J Sport Nutr 1996; 6: 307-320.
Dougherty K. A., Baker, L. B., Chow, M. and Kenney, W. L. Two percent dehydration impairs and six percent carbohydrate drink improves boys basketball skills. Med Sci Sports Exerc 2006; 38(9):1650-8.
Hoffman J. R., Stavsky, H. and Falk, B. The effect of water restriction on anaerobic power and vertical jumping height in basketball players. Int J Sports Med 1995; 16:214-218.

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