Isotonic drinks are not necessary for every workout, and for most training sessions up to 1 hour, plain water is enough. Isotonic drinks are mainly useful during long or intense exercise, usually longer than 60–90 minutes, especially in hot weather or with heavy sweating.
Isotonic drinks contain water, carbohydrates, and electrolytes, mainly sodium, so people use isotonic drinks to replace fluid and sodium losses and to provide extra energy during prolonged exercise. Choosing a sports drink makes sense when the drink matches the duration, intensity, and conditions of a specific workout.
The short version
- Isotonic drinks are one type of sports carbohydrate-electrolyte drink, and isotonic drinks have an osmolality close to blood plasma.
- Water and regular meals are usually enough for workouts under 1 hour in comfortable conditions.
- Sports drinks are more useful during exercise longer than 60–90 minutes, especially in heat or with heavy sweating.
- Alcohol-free beer can be an option after exercise, but current research does not show that alcohol-free beer replaces specialized sports drinks during long exercise.
- A homemade drink with water, a little salt, and a carbohydrate source can work, but a ready-made isotonic drink has a standardized composition.
What types of sports drinks are there?
Sports drinks differ by osmolality, which means the concentration of dissolved substances compared with blood plasma. Osmolality determines whether a drink is better at replacing lost fluid quickly or at providing extra energy.
Hypotonic drinks have a lower osmolality than blood plasma, so people use hypotonic drinks when the main goal is to replace fluid losses quickly and the need for extra carbohydrates is small. Isotonic drinks have an osmolality close to blood plasma, and isotonic drinks contain water, sodium, and carbohydrates in a concentration that helps replace fluid and sodium losses while also providing energy during prolonged exercise.
Hypertonic drinks have a higher osmolality than blood plasma and contain more carbohydrates. Hypertonic drinks are used mainly after exercise to restore glycogen stores or at certain stages of ultra-endurance events, because hypertonic drinks leave the stomach more slowly during ordinary training and can cause discomfort.
The name on the label matters less than the composition of the drink. The carbohydrate and sodium content of a sports drink should match the duration, intensity, and conditions of a specific training session.
Who needs isotonic drinks and why?
Isotonic drinks are useful when exercise is long or intense enough to cause noticeable fluid, sodium, and energy losses. During training, the body loses water and electrolytes through sweat, mainly sodium, and during longer or harder exercise, glycogen stores also gradually decrease.
Water and regular food usually compensate for these losses when a workout lasts less than 1 hour and takes place in comfortable conditions. Sports drinks can help more when exercise lasts longer than 60–90 minutes, especially in hot weather or with heavy sweating, because sports drinks replace fluid and sodium while also providing carbohydrates.
Specialists therefore more often recommend isotonic drinks during long training sessions and endurance competitions such as running, cycling, and triathlon. Most people who train in the gym for 40–60 minutes or do moderate physical activity do not need special products, because plain water and balanced meals are usually enough.
Is alcohol-free beer really a good isotonic drink?
Alcohol-free beer is sometimes called an isotonic drink, but alcohol-free beer is not the same as a specialized sports drink. Some types of alcohol-free beer have an osmolality close to sports drinks, and alcohol-free beer is about 90–95% water and contains carbohydrates, small amounts of electrolytes, and polyphenols from malt and hops.
Several studies led to comparisons between alcohol-free beer and isotonic drinks, but those studies do not show that alcohol-free beer works as a hydration drink better than classic isotonic drinks. One well-known study involved 277 marathon participants who drank polyphenol-enriched alcohol-free beer daily for 3 weeks before the race and 2 weeks after the race, and that study did not assess alcohol-free beer as a hydration tool or compare alcohol-free beer with specialized sports drinks.
The main difference between alcohol-free beer and sports drinks is composition. Isotonic drinks contain sodium and carbohydrates in amounts designed to replace what is lost during prolonged exercise, while alcohol-free beer usually contains less sodium and can vary a lot in carbohydrate content and osmolality depending on the type and producer.
Alcohol-free beer can be considered as one option after exercise if a person likes the taste and has no medical contraindications. Specialized sports drinks are usually preferred during long training sessions and competitions.
Do all people need an isotonic drink, or is water enough?
Most people do not need an isotonic drink for ordinary exercise, and plain water is enough for many workouts. For people who spend 40–60 minutes in the gym, run at an easy pace, or attend group classes, water usually replaces fluid losses well enough, and meals replace energy and electrolytes.
The situation changes during prolonged exercise, usually longer than 60–90 minutes, especially in hot weather or with heavy sweating. During a marathon, a cycling race, a triathlon, or long game-based training, the body loses not only water but also a significant amount of sodium, while glycogen stores are gradually used up.
Sports drinks do not protect against hyponatremia by themselves. Hyponatremia more often develops not only because sodium is lost in sweat, but because a person drinks much more fluid than is lost through sweat during exercise.
Mineral water also helps replace fluid loss, but mineral water compositions differ a lot and mineral water contains almost no carbohydrates. Mineral water therefore cannot fully replace a sports drink during long exercise.
Isotonic drinks are not a universal part of every workout, and isotonic drinks are not mainly designed for weight loss or muscle gain. A standard 500 ml bottle of an isotonic drink usually contains about 100–150 kcal and 15–30 g of sugars, so for many moderate workouts, a large part of the energy spent can be replaced immediately by the drink itself.
For most people who go to the gym a few times a week or do fitness for general health, plain water is enough. People who truly need isotonic drinks usually already know that need from the nature of their training and from advice given by a coach or a sports doctor.
Can you make an isotonic drink at home?
Yes, you can make a homemade isotonic-style drink. A homemade drink based on water, a small amount of salt, and a carbohydrate source such as sugar, honey, or fruit juice can help replace part of the fluid, sodium, and carbohydrate losses after prolonged physical activity.
A homemade drink is harder to balance than a commercial isotonic drink. Too many carbohydrates can make the drink leave the stomach more slowly and can make the drink harder to tolerate during exercise, while too little salt can make sodium replacement less effective.
One home recipe given by the article's expert includes 500 ml of water, a pinch of salt at about 1 g, half a lemon, and 1 teaspoon of honey or sugar. Ready-made isotonic drinks are more convenient because the carbohydrate and sodium content is standardized.
When is water enough and when does an isotonic drink make sense?
Water is enough for most workouts up to 1 hour, and an isotonic drink makes more sense during long and intense exercise. Sports drinks are generally more relevant for exercise longer than 60–90 minutes, especially in hot weather or with heavy sweating.
Alcohol-free beer can be considered as one post-workout option, but there is still no convincing evidence that alcohol-free beer can replace a specialized sports drink during prolonged physical activity. Choosing a sports drink should depend on the task the drink solves, not on the idea that every sports drink is automatically useful for everyone.
Common questions
What is an isotonic drink?
An isotonic drink is a type of sports drink with an osmolality close to blood plasma. An isotonic drink usually contains water, carbohydrates, and electrolytes, mainly sodium.
Is water enough after a normal workout?
Water is usually enough after a normal workout that lasts 40–60 minutes or less and takes place in comfortable conditions. Regular meals usually replace the energy and electrolytes lost during that kind of training.
When should you drink an isotonic drink?
An isotonic drink is usually more useful during exercise longer than 60–90 minutes, especially in hot weather or with heavy sweating. An isotonic drink helps replace fluid and sodium losses while also providing carbohydrates.
Can alcohol-free beer replace an isotonic drink?
Alcohol-free beer can be one option after exercise, but alcohol-free beer is not the same as a specialized sports drink. Current studies do not show that alcohol-free beer replaces classic isotonic drinks during long exercise.
Can I make an isotonic drink at home?
Yes, a homemade drink with water, a little salt, and a carbohydrate source can work as a simple option. A ready-made isotonic drink is easier to use when you want a standardized amount of carbohydrates and sodium.