Sports Drinks

By Kerry O’Brien. E-mail: kobrien@psy.otago.ac.nz

Sports drinks first emerged in 1958 when Louisiana State University produced a sugary electrolyte drink called “Bengal Punch”. In the mid 60’s the University of Florida produced a somewhat more palatable drink called “Gatorade” which saw the adoption and popularisation of the sports drink within the fitness and sports community. The sports drink industry is now worth over $US 6 Billion world-wide. The multitude of different brands on the market leaves the consumer somewhat baffled as to what choice to make, which is not surprising given that each proclaims to be better than the rest. But are sports drinks really beneficial to us, and how should we decide what, when and how to use them?

Why Use Sports Drinks

Avoidance of dehydration: The body is 67% water, when we exercise for extended periods of time, especially in warm conditions, we loose large amounts of water through sweat. With as little as a 2% decrease in body weight via sweating, we experience impaired physical performance. A 5% decrease results in heat exhaustion, and later delusions and hallucinations. A 10% decrease results in circulatory collapse, and potentially death, as seen in a number of NFL gridiron players in the past 3 months.
Most sports drinks contain important electrolytes, such as sodium (salt) and potassium, which replace what is lost when we sweat. Maintaining the correct balance of electrolytes is important for both peak performance and avoiding cramp.
Sports drinks provide energy to the body in the form of simple carbohydrates or sugars (glucose, fructose, and maltodextrines). These carbohydrates quickly replace lost muscle glycogen and provide the energy necessary for extended periods of exercise.
The combination of electrolytes and carbohydrates aids in the absorption of water back into our bodies, but only if the carbohydrate levels in the drink are kept to between 4% and 8%. Too much carbohydrate in a drink will inhibit absorption of fluid.
Lastly, and perhaps most importantly, sports drinks are convenient. If we need to replace lost energy quickly, maybe because we have got another game of tennis soon, then it is much easier to drink down some energy than sit down and eat a meal.

What and When to use Sports Drinks

Sports drinks can be divided up into 3 general groups based on their carbohydrate and electrolyte concentrations. These are Isotonic, Hypotonic, and Hypertonic.

Isotonic sports drinks contain small amounts of electrolytes and between 5% and 8% carbohydrate. This is equivalent to 120-170 kcal per 500ml bottle. An isotonic drink is excellent for use both during exercise and after exercise, and provides the optimal balance for fluid re-hydration. Most big name sports drinks (Gatorade, Powerade, Lucozade Sport and All Sport) are isotonic. This type of drink should be used in most circumstances where you exercise intensely for more than an hour.
Hypotonic sports drinks contain low levels of carbohydrate (2%-3%), with moderate levels of electrolyte, and should be used in situations where you may be sweating a lot but not necessarily using a lot of energy. For example sprint work, playing cricket, or sitting in a hot stuffy office.
Hypertonic sports drinks contain around 10% to 15% carbohydrates (240-320 kcal per 500mls) with similar amounts of electrolytes as other sports drinks. These types of drink are suitable for post exercise replenishment of muscle glycogen stores. Ideally, these drinks will be used by marathon runners and serious weight trainers who rely on high glycogen levels to prevent breakdown or catabolism of muscle following exercise. Hypertonic drinks are not suitable for re-hydration during exercise, as the high concentration of carbohydrates inhibits fluid absorption.

Conclusions

In general you should probably stick with isotonic sports drinks. The choice you make between brands should be based on the palatability of the drink, as there is little difference between the top brands as far as effectiveness is concerned. Go for the sports drink you enjoy, that way you will drink more and re-hydrate quicker, but try to avoid carbonated drinks as they cause bloating and may prevent you from properly re-hydrating.

Don’t let thirst be the indicator of when to have a drink, by the time your body tells you it is thirsty, it is too late and performance will be compromised. If you start to sweat, it is time to start drinking.
Keep an eye out for new sports drinks that contain protein. Recent research indicates that a combination of carbohydrates and protein may be more effective at restoring energy levels and preventing muscle breakdown due to energy depletion. Ideal for those who do circuit or weight training.