Isotonic, hypotonic, hypertonic – the world of sports drinks can be confusing. The variety of fluids you can stick in your bottle sound more like a superhero’s powers than a simple drink designed to hydrate, replace electrolytes and give you energy on the go
. So what do all the terms mean? What are the benefits of each drink? And what should you be sipping when? We’re glad you asked. 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 working out 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 than 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 than blood
Each drink has different benefits to support your training. Here’s the gen on what to use when and why. Hypotonic sports drinks
Best for: Rapid rehydration When to use: Pre-hydration, on shorter workouts, on long rides, in hot weather; when you need a drink to rehydrate quickly & effectively.
What exactly are hypotonic drinks? Hypotonic drinks have a lower concentration 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.
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 the dreaded GI distress that can come with other energy drinks too.
Hypotonic drinks will also give you a speedy top-up of electrolytes – 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 Sunday long run or have an epic day in the saddle planned, use these drinks in combination with your other nutrition Isotonic sports drinks
Best for: Carbohydrate release When to use: Shorter duration or high-intensity workouts; when you want carbohydrates over hydration during endurance exercise.
What exactly are isotonic drinks? Isotonic drinks have a similar water, salt and carbohydrate concentration (6-8%) to blood. They typically provide more energy and electrolytes than a hypotonic drink but take longer to enter the bloodstream.
How do isotonic sports drinks work? Isotonic drinks are a source of carbohydrates to give you energy as you workout 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 than hypotonic drinks so energy and electrolyte release is slower.
What are the disadvantages of isotonic drinks? Many commercial 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 you’re prone to GI issues, you may find watering down isotonic drinks makes them easier on your digestive system. Though this will change the rate at which they enter the bloodstream. Hypertonic sports drinks
Best for: Large doses of carbohydrate When to use: As a recovery drink after intense or sustained exercise, for extra carbohydrates in the lead up to a race.
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. What else to look for when choosing the best sports drink for you
The taste: It’s easy to get caught up in carb content and electrolytes when choosing a sports drink but don’t forget about the basics, like does it taste good? If you don’t like the flavour or texture you probably won’t drink enough and rehydrating becomes a chore rather than something to look forward to.
Natural ingredients: Artificial additives, sweeteners and ingredients you can’t pronounce offer little in the way of nutritional value and can play havoc with the gut when exercising.
Extra power: If you want your drink with an added kick, look for drinks that contain caffeine. While caffeine isn’t a source of energy in the way sugar is, it does have proven benefits to anyone trying to exercise for extended periods of time. It acts as a mild central-nervous-system stimulant that can improve alertness and concentration and perk you up if you are feeling tired or lethargic. In practice, that means some well-timed caffeine can help you go harder and for longer. It also encourages our bodies to burn fat as fuel and it can reduce feelings of pain and fatigue.
And remember, as with any and all kit and equipment, don't leave trying out new products until race day.
