Getting enough fluids during and after exercise is important in any sport. Dieticians Shelley Meltzer and Cecily Fuller of the Sports Science Institute take a look at the importance of fluids on rugby performance.
Why fluids are important
Fluid plays a significant role in optimising rugby performance. Fluid is important to maintain adequate hydration and can also be a practical source of nutrients such as carbohydrate (and protein if needed) and electrolytes. By increasing the production of saliva, which has anti-microbial properties, fluid may impact on immune function (fighting infection).
Research shows that athletes who do not drink anything during exercise will perform less well than they would if they drank ad libitum (according to thirst). If players are more than 2% dehydrated and thirsty in warm to hot conditions, performance will be impaired.
Fluids can also be an important and practical source of carbohydrate for a rugby player. An important role of fluid is to regulate body temperature and prevent heat illness that may result if the rate of heat production by the body exceeds the rate of heat loss, and total body temperature rises to a level that leads to organ dysfunction and collapse.
Risk of over-heating
There are several factors that may contribute to the risk of developing heat illness and it should be noted that drinking will not prevent heat stroke, as there are many other contributing external and internal factors.
External factors include ambient temperature; radiant heat (direct sunlight); humidity; wind; exposure time; clothing (e.g. dark clothing), headgear, shoulder pads, and medication, as well as stimulants such as pseudoephedrine and caffeine. Internal factors include a past history of heat intolerance; body size and composition; aerobic fitness; acclimatisation; pre- and during- exercise hydration levels; and viral illness, e.g. upper respiratory tract or gastroenteritis.
It is therefore recommended that players are closely monitored and individually assessed on a daily basis, when exercising in a hot environment. Any player demonstrating signs or symptoms of heat stress should be removed immediately from training or playing.
Signs of dehydration
Early signs of dehydration are headache, fatigue, loss of appetite, flushed skin, heat intolerance, light headedness, dry mouth and eyes, and dark urine with a strong odour. Advanced signs require urgent medical intervention and include difficulty in swallowing, clumsiness, shrivelled skin, sunken eyes and dim vision, painful urination, numb skin, muscle spasms, “abnormal behaviour”, and delirium.
Note that there is the risk of players over-drinking and this in itself may have risks. For example, it has been reported that American football players, in an attempt to prevent heat cramps, over-hydrated by drinking too much water.
Signs of over-hydration include: nausea, vomiting, extreme fatigue, respiratory distress, dizziness, confusion, disorientation, oedema (rings, shoes, watches may feel tight), coma, seizures, and even death if left untreated.
How much fluid to take before and during?
Rugby is a team sport played by athletes of varying stature where the game is of an intermittent nature and limited to two 40-minute halves. The intermittent nature of the sport probably allows for greater access to fluid intake during competition when compared with endurance events.
As a rough guide, drink between 500-800ml per hour if you are a 70-90kg player. Heavier players may require more, and in hot or humid weather conditions all players should drink more.
Body weight can be used as a general guideline and to encourage an increased awareness of individual fluid requirements. Players should be weighed before and after exercise in minimal clothing, and corrected for urine losses and drink volume.
More is not better – drink according to guidelines and caution not to over-interpret these recommendations or be overenthusiastic. Fluid should also be provided at meal/snack times to encourage players to drink.
Fluid absorption is best if the stomach is kept partially filled during exercise. This can be achieved by drinking 250-500ml immediately before players run on to the rugby field and then adding an extra 100ml every 10 minutes (or as close to that as possible) during the match – providing approximately 600ml per hour.
How much fluid after training or a match?
After exercise, players continue to lose fluid by sweating or urinating, so they need to replace fluids and drink at regular intervals. Remember that carbohydrate-containing drinks will also help minimise any muscle damage and will restore muscle energy stores more rapidly. A small amount of protein should be included. Players should avoid alcohol in the recovery period as alcohol encourages further fluid losses.
Using the calculated difference between pre- and post- body weights can also be used to give an indication of how much fluid is needed for rehydration. A general guideline of a volume equal to 150% of the fluid deficit is often recommended when players only have two to four hours post-training to fully rehydrate. Otherwise players will make up these deficits by eating and drinking regularly.
What types of fluids are best?
Carbohydrate should be included in the drink at a concentration of 5-8% and the drink should contain a small amount of sodium (salt). More sodium is required in hotter conditions and these requirements can be met by commercial oral rehydration powders and/or by adding extra salt to food and salty snacks.
Sports drinks and sports drink powders (at the recommended concentration) that can be mixed with water are therefore the ideal choice. Water is not the ideal drink during a match or when training.
Tips for taking in more fluids
Take personally labelled drinks to practise
Players must familiarise themselves with their own fluid requirements in different environmental conditions – in hotter and more humid conditions they may need to drink more
Include fluid breaks when training
Ensure drinks are cool as they taste better than warm drinks
Encourage flavours that are enjoyed, as players will then tend to drink more
Cooling strategies are very important to prevent heatstroke in hot conditions. These include staying in the shade during breaks and removing warm jerseys; using cold-water ice packs and side-line fans, etc.
Allowing athletes to acclimatise to hot conditions for seven to 10 days should also be a component of managing potential heat illness.
Why alcohol is a bad idea
In team sports, the culture may often promote post-game alcohol binges. Alcohol reduces reaction time, and impairs balance, accuracy, hand-eye co-ordination, strength, power and endurance, and impairs body temperature regulation. Alcohol also increases high-risk behaviour that may lead to poor judgement and reduced inhibition, accidents, injuries and even death.
Alcohol also distracts from sound recovery strategies, injury treatment and sleep. Drinking alcohol after a match interferes with the recovery of the body’s carbohydrate stores, and acts as a diuretic, thereby increasing urinary fluid losses and so delaying rehydration.
Alcohol also has a vasodilatory effect, which can increase bleeding and swelling, thus delaying or slowing recovery of soft-tissue damage and rehabilitation from injury. With an energy density of 29kJ (7kcal)/gram, alcohol can contribute significantly to daily energy intake, causing fat gain. Alcohol may also lead to increased storage of dietary fat, as it is a preferred fuel and so suppresses the oxidation of fat, which is then stored.
Practical tips for avoiding alcohol
1. Adhere to the 24-hour rule, i. e. - avoid alcohol in the 24 hours before a match and in the 24 hours after a match, if any soft tissue injuries or bruising have occurred. Some teams may have a ban on alcohol intake.
2. Ensure that plenty of non-alcoholic drinks are available after training or a match. Those players who choose to drink alcohol should ensure that they are adequately rehydrated and refueled with carbohydrates and fluid before drinking alcoholic drinks which in any case should be limited.
3. Note that although some alcoholic beverages do contain carbohydrate (e. g. beer) the alcohol content of the drink is a diuretic and inhibits the restoration of glycogen in the muscles. This affects performance and recovery therefore players should rather resort to other more appropriate sources of carbohydrate.
Source: Practical Nutrition for Rugby by Dieticians Shelley Meltzer and Cecily Fuller, courtesy SA Rugby.
(Health24, August 2011)