1. A hypotonic drink contains less than 4g of carbohydrates per 100ml and has low osmotic pressure. This is intended as a thirst quencher. Hypotonic drinks give the athlete little energy in the form of sugars. A hypotonic sports drink is taken up by the body more quickly than just water. Ideal for shorter or less strenuous exertion.
2. An isotonic drink contains between 4g and 8g of carbohydrates per 100ml and has about the same osmotic pressure as bodily fluids. An isotonic drink is taken up by the body about as quickly as water. They are intended to quench thirst and provide energy to the body. Ideal for endurance sports such as marathons and ultra-marathons.
3. A hypertonic drink generally has more than 8g of carbohydrates per 100ml and greater osmotic pressure than bodily fluids. It is primarily intended to supply energy. The thirst quenching effect is secondary. Hypertonic drinks are taken up more slowly than water. Ideal for use 30 to 60 minutes before sports/training/exertion and immediately after sports/training/exertion. Hypertonic drinks are also useful for athletes who find that they need a bit more energy during their training.
How to choose the correct sports drink:
• Aim to choose an Isotonic OR Hypertonic sports drink especially when running long distances
• Carbohydrates: Choose drinks that include a mixture of different carbohydrate sources such as glucose, fructose, sucrose and maltodextrin as far as possible, especially at the start of a long distance run or a marathon.
The guideline for carbohydrate consumption during a marathon or long distance running is 30-60 grams of carbohydrates per hour. Thus the sports drink will contribute to your carbohydrate consumption, but it is advisable to visit a dietician to customise your plan during a marathon/race to ensure an optimal consumption.
• Electrolytes which play an important role in water balance in the body:
Sodium: Sodium is lost through sweat and needs to be replaced. Having sodium in the drink also increases thirst, which helps you to drink more water and stay hydrated.
Potassium: Potassium is also lost through sweat.
Calcium and Magnesium are sometimes included in sport drinks that might contribute to reduce the risk of muscle cramping
• A good sports drink does not need to include added amino acids, oxygen, caffeine or herbal ingredients.
It is advisable to not take Fizzy drinks and sodas to replenish your electrolyte imbalances that occurs during running, due to a lack thereof. If chosen to have fizzy drinks as part of your carbohydrate intake during a run, then it should be diluted with water and additional electrolyte intake will be necessary. Also, the carbonated gas in fizzy drinks and sodas could lead to bloating and discomfort and can make it hard to drink enough fluid during the race and to keep well hydrated.
The nutritional needs for every runner (though sticking to specific given guidelines) prior, during and after running remains to be unique…what works for one, won’t necessarily work for another.
Choose sports drinks wisely!
Dianda Snyman RD(SA) & Hesté-Marie Viviers RD(SA)
Registered Dieticians with a special interest in sports nutrition
Pr No 084 000 0109991