Depending on the duration and intensity of your training, choosing the right type of sports drink can make a big impact on your hydration and energy level. There are so many sports drink options to choose from. Some may contain a higher percentage of carbs per serving defined by the tonicity, or the amount of solute or “thickness” of one solution compared to another.
To calculate the carbohydrate concentration in sports drinks, use the following calculation:
Reference: Carbohydrates The Master Fuel- USADA.ORG.
When we compare the tonicity of a sports drink we compare it to human blood, which impacts how quickly you can absorb the fluid into your bloodstream. Sports drinks can be either hypotonic (lower concentration), isotonic (about the same concentration as human blood), or hypertonic (higher concentration).
Hypotonic Sport Drinks
Hypotonic sports drinks are best used for endurance events since they are absorbed quickly into the bloodstream to help maintain hydration. Since the solution has a lower concentration than blood, fluids cross the gut into blood vessels more easily, preventing GI issues and “sloshing” when training for longer events.
Hypotonic drinks are lower in carbohydrate (less than 6%) and are used primarily for hydration rather than fueling for endurance events. If you are using a hypotonic sports drink, like Skratch or Osmo hydration, you’ll need fuel from solids such as gels, bars or chews to help maintain energy.
Isotonic Sports Drinks:
Isotonic sports drinks are best used for short-duration, high-intensity training. Sports drinks such as Gatorade (6-8% carbohydrate) have a similar concentration to blood and provide enough carbs for quick energy but are not the best at hydration.
If your training is short (less than an hour) and you need a quick energy source, an isotonic sports drink is the better choice, but it can cause GI issues if consumed in large quantities, especially when combined with a high carb food such as gels and bars. This is why isotonic sports drinks are not recommended for endurance events. Just make sure you are not combining drinking regular Gatorade (or other isotonic drinks) to wash down your energy gel during races.
Hypertonic Sports Drinks
Hypertonic sports drinks are best used for recovery or to fuel high-intensity training. Hypertonic sports drinks have a higher concentration than blood and are beneficial to deliver a large amount of calories quickly if you cannot consume nutrition from solid foods or sports nutrition products during training. Some hypertonic sports drinks, such as Maurten 320, contain as much as 80 grams of carb per 500 mL. If you struggle consuming 30-60 grams of carb from solids during an endurance event, liquid calories may be easier to digest and are better absorbed than solids.
The downside to using just a hypertonic sports drink for fueling during endurance events is the risk of dehydration. The high concentration of fluid in your intestine becomes hypertonic. This means that the fluid must move water out of your bloodstream back to the intestine so it can dilute and absorb the nutrients in your gut. However, this process leads to dehydration since the water has to move from your blood into the intestine rather staying in your bloodstream resulting a decreased blood volume and potential dehydration.
Hypertonic sports drinks can cause GI issues as well, therefore should only be used for quick energy for recovery rather than for hydration.
Take Home Message
Depending on the type of training you are doing, choosing the right sports drink can make a big difference on your hydration, energy, and overall sports performance. In general, endurance athletes should use more hypotonic sports drinks to prevent dehydration and to use solids for fueling, rather than relying on a high carb sports drink risking GI issues and potential dehydration. When in doubt, consult your sports dietitian on which sports drink is best for you.