The regular ingestion of fluids is essential for sporting performance.
Hypohydration (total body water below normal) impairs the body’s ability to regulate heat resulting in increased body temperature and an elevated heart rate. Sports drink.
Perceived exertion is increased causing the athlete to feel more fatigued than usual at a given work rate.
Mental function is reduced which can have negative implications for motor control, decision making and concentration.
Gastric emptying is slowed, resulting in stomach discomfort. All these effects lead to impairment in exercise performance.
Most types of exercise are adversely affected by hypohydration, especially when they are undertaken in hot conditions, and negative effects have been detected when fluid deficits are as low as 2% (i.e. a deficit of 1.2 litres for a 60 kg athlete).
The good news is that by drinking regularly during exercise, athletes can prevent declines in concentration and skill level, improve perceived exertion, prevent excessive elevations in heart rate and body temperature and improve performance – good justification for every athlete and coach to make fluid replacement a key priority during training and competition.
It is impossible to prescribe a general fluid replacement plan that will meet the needs of all athletes.
Fortunately, athletes can easily estimate their own fluid requirements by weighing themselves before and after exercise sessions.
Each kilogram (kg) of weight lost is equivalent to approximately one litre (L) of fluid.
Adding on the weight of any fluid or food consumed during the exercise session will provide an estimate of total fluid loss for the session.
For example, an athlete who finishes an exercise session 1 kg lighter and has consumed 1 litre of fluid during the session has a total fluid loss of 2 litres.
Once an athlete’s individual sweat losses are known, a plan can be prepared to help the athlete achieve better fluid replacement in subsequent exercise sessions.
Fluid replacement plans will differ according to the athlete and the opportunities for drinking during the sport. However, where possible it is better to begin drinking early in exercise and adopt a pattern of drinking small volumes regularly rather than trying to tolerate large volumes in one hit.
Most athletes can tolerate 200-300 ml every 15-20 minutes but tolerance will vary according to the exercise intensity.
Typically athletes replace 30-70% of sweat losses during exercise.
Fluid replacement is an issue for all sports including those such as swimming and water polo conducted in wet environments, and sports conducted in air conditioned stadiums.
There are many reasons for athletes failing to drink enough to replace fluid losses.
Some athletes are so focused on training or competing that they forget to drink. Some avoid drinking because they fear stomach discomfort.
Drinks need to be cool, palatable and conveniently available or they will not be consumed.
What should athletes drink
Research shows that fluid intake is enhanced when beverages are cool (~15 °C), flavoured and contain sodium (salt).
This makes sports drinks an ideal choice during exercise.
They are legitimate products that are well researched and proven to improve fluid intake and performance.
A great deal of science has gone into developing the flavour profile of sports drinks so that they encourage fluid intake during exercise. In addition, sports drinks contain carbohydrate at a concentration (4-8%) that allows refueling to take place during exercise.
Several studies demonstrate that use of sports drinks will improve fluid intake.
In the past, it was believed that sports drinks only benefited the performance of exercise greater than 90 minutes.
However, in recent years, the intake of carbohydrate and fluid has been shown to be beneficial for high intensity exercise of approximately 60 minutes.
This makes sports drinks a good option for many types of sporting activity.
Sports drinks are beverages whose stated purpose is to help athletes replace water, electrolytes, and energy before and after training or competition.
Which sports drink is best
Sports drinks can be split into three major types:
• Isotonic sport drinks contain similar concentrations of salt and sugar as in the human body.
• Hypertonic sport drinks contain a higher concentration of salt and sugar than the human body.
• Hypotonic sport drinks contain a lower concentration of salt and sugar than the human body.
Most sports drinks are approximately isotonic, having between 4 and 5 heaped teaspoons of sugar per five ounce (13 and 19 grams per 250ml) serving.
Athletes actively training and competing lose water and electrolytes by sweating, and expending energy.
Sodium in drinks might help to avoid hyponatraemia (low sodium), but only after sustaining athletic activity for more than four hours.
A sports drink containing sodium may be appropriate for recovery from intense and prolonged training or competition.
A stated purpose of sports drinks, which provide many calories of energy from sugars, is to improve performance and endurance.
Sports Drinks can be used:
• Before exercise to provide a little extra fuel;
• During physical activities that last longer than 60 minutes of non-stop exercise;
• During and in-between multi-events (e.g. swim meets, soccer tournaments);
• After exercise to help restore carbohydrates, electrolytes and fluids lost.
The selecting a suitable sports drink isn’t always an easy task as the composition of these drinks can vary from product to product, especially their carbohydrate and sodium content.
To make this even more confusing, there are a variety of beverages that may be perceived to be sports drinks, but technically are not designed to aid sport performance.
True “sports drinks”: Carbohydrate, electrolyte beverages
E.g., Gatorade™, Powerade™, eLoad™, Accelerade™
Ideally consist of:
• 6-8% carbohydrate (i.e., 6 to 8 grams of carbohydrate for every 100 ml of beverage)
• 500-700 mg of sodium per litre
• 80-200 mg of potassium per litre.
Purpose: replace energy (carbohydrates), electrolytes (e.g. sodium, potassium), and fluids lost as a result of physical exercise.
Low-Calorie Electrolyte Drinks: Artificially sweetened, provide electrolytes & fluids.
• E.g., G2™, Nuun™
• Purpose: provide fluids and electrolytes only
• Usage: when no need for carbohydrates in a drink, but want to replenish electrolytes and fluids lost with sweat.
Will not enhance endurance as they contain no carbohydrates.
Vitaminized Water: Water with vitamins added and possibly carbohydrates.
• E.g. Aquafina Plus™, Vitamin Water™
• Purpose: promoted as a “healthy” type of water.
• Usage: not a replacement for a healthy diet; could result in consumption of too many random vitamins; may be too high in sugar for use during exercise.
Energy Drinks: Source of caffeine, taurine, carbohydrates, vitamins, possibly herbs.
• E.g. Red Bull™, Rockstar™
• Purpose: promoted to boost energy levels and improve mental concentration.
• Usage: only provide short-term perception of energy.
caffeine content is usually excessive for children and/or for those not accustomed to regularly consuming caffeine.
May be too high in sugar for use during exercise.
Is it possible to drink too much?
Consuming fluid in excess of requirements may cause some gastrointestinal discomfort.
In extreme cases, a condition called hyponatraemia can occur.
Hyponatraemia (low blood sodium levels) causes symptoms similar to dehydration and is potentially life threatening.
It is not common but can occur in prolonged endurance events (> 2 hours) when large volumes of low sodium drinks (such as water) are consumed and sweat losses are small.
Those most at risk are small females who have long race times.
This group of athletes tends to have small sweat losses and plenty of time to consume large amounts of fluid during the event.
Consuming sodium-containing fluids such as sports drink and matching fluid intake to sweat loss lowers the risk of hyponatraemia.