Sports Drinks Hypotonic, Isotonic and Hypertonic What’s the difference?

The world of sports drinks, what to put in your body and when to put it in can be very confusing. The variety of fluids you can stick in your bottle sounds more like a medical procedure than a simple drink designed to hydrate, give you energy and replace electrolytes on the go.

So, what do all these terms mean? What are the benefits of each drink? And when and where should you be drinking them? Here’s everything you need to know.

Know your tonicity

Sports energy drinks are broken down into three different types depending on their concentration compared to the human body or tonicity to give it a technical name.

The tonicity of a drink is important when you’re training as it affects the amount of carbohydrates, electrolytes and fluids that enter your bloodstream and how quickly you can absorb them to boost your performance. The three commonly seen types of sports drinks are:

. Hypotonic – which has a lower concentration of fluid, sugars and salt then blood.

. Isotonic – which has a similar concentration of fluid, sugars and salt to blood.

. Hypertonic – which has a higher concentration of fluid, sugars and salt then blood

Each drink has different benefits to support your training. Here’s the "gen" on what to use and when you can use them to improve your performance.

Hypotonic sports drinks

Best for: Rapid rehydration

When to use: Pre – hydration, sipping throughout shorter workouts, on long workouts in hot weather; when you need a drink to rehydrate quickly and effectively. The primary goal of this drink is hydration rather then delivery of large amounts of energy.

What exactly are hypotonic drinks?

Hypotonic drinks have a lower concentrate of carbohydrates (>5%) and salt than blood. This means they are absorbed into the bloodstream at a faster rate for quick hydration and electrolyte release. Hypotonics may contain carbohydrates too, helping to contribute towards your total energy intake. You can check the energy contents on most the packaging of your electrolyte’s drinks.

How do hypotonic sports drinks work?

When you drink a hypotonic drink, the solution moves via osmosis across the gut walls and into the blood vessels. This means fast rehydration, as the drink is rapidly absorbed across the gut lining and quickly replaces fluids lost. There’s a much lower risk of bloating, cramps and toilet problems that can come with other energy drinks.

Hypotonic drinks will also give you a quick top up of electrolytes and those vital salts and minerals lost in sweat – to help regulate muscle function and keep your fluid levels balanced.

What are the disadvantages of hypotonic drinks?

Hypotonic drinks focus on rehydration and therefore do not provide maximum carbohydrates (energy). If you’re out on a long run or have an epic day in the hills on the bike, use these drinks in combination with your other nutrition, such as quality food, energy bars and gels.

Examples of hypotonic drinks

• Hydralyte Sports

• Mizone

• SOS Hydration Drink Mix

• G Active and G2

• Powerade Zero

• Endura Rehydration Low Carb Fuel

• Nuun Electrolytes

• Shotz Electrolyte tablets

• Skratch Labs Sport Hydration Drink Mix

• Aqualyte Solution

• High 5 Zero

Isotonic sports drinks

Best for: Carbohydrate release

When to use: Isotonic drinks are generally most useful for shorter duration, high intensity exercise were getting carbs in quickly can be more important than warding off dehydration.

What exactly are isotonic drinks?

Isotonic drinks have a similar water, salt and carbohydrate concentrate (6-8%) to blood. They typically provide more energy and electrolytes than a hypotonic drink but take a little longer to enter the bloodstream. Theoretically they deliver a reasonable amount of energy and clear the gut promptly too, if not quite as fast a hypotonic solution.

How do isotonic sports drinks work?

Isotonic drinks are a source of carbohydrates to give you energy as you train and help replace the fluids and electrolytes lost through sweat. The trade-off for extra carbs is that isotonic drinks require more energy to get across the gut wall then hypotonic drinks, so energy and electrolytes release slower.

What are the disadvantages of isotonic drinks?

Many of the commercial “jack of all trades” sports drinks on the market are isotonic but a quick look at the ingredients often reveals high levels of sugars, sweeteners and additives which can cause stomach cramps and bloating. If your prone to stomach problems whilst training and competing, then watering down your isotonic drinks makes them easier on your digestive system. Although this will change the rate at which they enter the bloodstream.

Examples of Isotonic drinks

· Powerade ION4

· Staminade

· Science in Sport – GO Electrolyte

· Pure Sports Nutrition – Pure Electrolyte Hydration

· Endura Rehydration Performance Fuel

· GU Hydration Drink Mix

· Gatorade Endurance

Hypertonic sports drinks

Best for: Large doses of carbohydrate

When to use: As a recovery drink after intense or sustained exercise and for extra carbohydrates in the lead up to a session/event/race. Hypertonic sports and recovery drinks are therefore most appropriate in scenarios were taking on energy and nutrients is the main priority and dehydration is insignificant.

What exactly are hypertonic drinks?

Hypertonic drinks contain a higher concentration of salt and sugar than blood, making them a good way to supplement your daily carbohydrate intake or top up glycogen stores. They’re usually used as recovery drinks and often contain added protein.

How do hypertonic sports drinks work?

Hypertonic drinks provide the highest dose of carbohydrates (>8%) of all energy drinks. Despite a slower absorption rate than hypotonic or isotonic drinks, they’re still a quick way to top up glycogen stores, as the body tends to absorb liquids more quickly than solid food.

What are the disadvantages of hypertonic drinks?

Hypertonic drinks can cause dehydration as the body has to move water from the bloodstream into the intestine to dilute the fluids before it can absorb them. This can make you feel thirsty and sometimes nauseous. While some ultra-athletes use hypertonic drinks alongside other hydrating drinks during exercise, they’re best drunk post-workout.

Examples of hypertonic drinks

• GU Roctane Energy Drink Mix

• Lucozade Energy

To summarise

Each of the above methods provide positives and negatives to help with your athletic performance.

Having awareness of your body and how you best perform goes a long way to help you decide which drinks to use and when to use them. Prior planning before training and competing will help you select your drink and prevent you from having to always rely on the commercial brands from out of the vending machine as a last-minute option.

Jordan Kerman BSc (Hons), MSc (Hons), BBCO Performance Director