Two metres of sports drinks, electrolyte tablets and powders on the shelf, and in front of them the question: do I even need this? For most sessions in the gym, the answer from sports nutrition is no – and it is formulated unusually concretely. There are amounts per hour, a time limit from which a sports drink becomes useful, and a single mineral with an evidenced place in it. This article clarifies what electrolytes are, when water is enough, what belongs in a sports drink and why drinking too much is a real risk.
What electrolytes actually are
Electrolytes are substances that can carry electrical charges in a solution. In the course documents, the term is applied above all to sodium, potassium and chloride – strictly speaking it would also cover the remaining macro and trace elements. All three are macro elements, that is, minerals with a requirement of more than 100 mg per day, involved in nerve conduction, muscle contraction and the regulation of water and acid-base balance.
They become a topic in sport by way of water: it is considered the first limiting nutrient, and a drop in performance can already occur at a loss of 2 per cent of body weight – around 1.5 litres at 75 kg. Basic intake for adults is two to three litres per day, of which only about half comes from drinking; more on this in the article Drinking in everyday life.
What you lose when you sweat
Sweat is water with dissolved substances, sodium first among them. How much adds up depends on how heavily you sweat – and the range is enormous. In strength training on machines or in health-oriented sport, the sweat rate is often below 0.2 litres per hour. Most people stay below 1.5 l/h, with 0.8 l/h already counting as relatively heavy sweating; world-class endurance athletes can lose more than 3.0 l/h. Temperature, humidity, body weight, intensity, fitness level, wind and clothing all have an influence.
Your own value is supplied by the weighing protocol: measure your weight directly before and immediately after exercise and note the amount you drank.
When water is enough – and when it is not
Here comes the clearest statement in the course. For athletes, the following applies as an addition to normal nutrition: 0.4 to 0.8 litres of sports drink extra per hour of sport – with water instead of a sports drink for a duration of under one hour. The reference value appears identically in several course documents and matches the ACSM guideline from 2007, which is still considered realistic.
For a gym session, a class or a 45-minute run, water is therefore the right choice. A sports drink becomes interesting when exercise goes beyond an hour, when several sessions are due in one day or when heat is added – for instance in Hyrox training or before a half marathon. Anyone who wants to lose weight, by contrast, opts for water during and after training.
What belongs in a sports drink
Carbohydrates
There is no ideal value; the target amount depends on the use. A sensible range is 30 to 90 g per litre, that is, 3 to 9 g per decilitre; most products are at 60 to 80 g per litre, with 6 to 8 g per decilitre being usual. Up to 60 g per hour it makes no difference whether only glucose is contained. From around 120 minutes of exercise, 60 g per hour or more is needed; above that – up to around 90 g – the drink should contain glucose and fructose, because the absorption routes for glucose are otherwise maxed out.
Sodium – and nothing else
The sentence from the nutrient script is unambiguous: today the macro element sodium is the only mineral with a justified place in sports drinks; from a scientific point of view there is no need for the other elements. Sodium promotes rehydration, and usual contents are 0.2 to 0.4 g per litre, corresponding to around 0.5 to 1 g of table salt.
Vitamins, further minerals or individual amino acids are neither necessary nor evidenced and can make the drink less well tolerated. The only other justified addition is caffeine. Why magnesium of all things is advertised so often is set out in a separate article.
Isotonic, hypotonic, hypertonic
Osmolality describes, in simplified terms, the number of dissolved particles per litre – regardless of their size. Ten individual glucose molecules give an osmolality of 10; if the same sugars are linked as maltodextrin, only 1. So the more multiple sugars, the lower the osmolality.
The terms describe the relationship to blood, which is at around 285 to 295 mmol/kg: hypotonic means fewer, isotonic the same number and hypertonic more dissolved particles. This is relevant because osmolality influences gastric emptying and absorption – hypertonic drinks more often cause gastrointestinal problems, isotonic ones are absorbed more quickly. On the label this only helps to a limited extent: in Switzerland a drink may count as isotonic even at 260 to 300 mmol/kg, in the EU the value is higher, and osmolality does not have to be declared anyway.
Mixing your own instead of buying
A sports drink needs three ingredients. The version for one litre of water or fruit tea: 30 g of sugar or fruit sugar, 50 g of maltodextrin and 1.5 g of table salt. That gives around 80 g of carbohydrate per litre with a low osmolality of about 184. Only as much salt as tastes tolerable.
The side effect concerns the teeth: pH values of commercial drinks measured in Switzerland in 2006 were practically all at 3 to 4 and were considered critical for tooth enamel – the self-mixed version with maltodextrin comes out at pH 6.9.
Heat, long exercise and the recovery afterwards
Before long exercise, prehydration is worthwhile: drink enough before you start, because a deficit is hard to make up along the way. During exercise a cool drink of 15 to 20 degrees is more pleasant, and you drink in small portions. Further precautions are in the article Training in the heat.
Afterwards it is about making up the loss. Because part of the fluid is lost via urine, 1:1 is not enough; around 150 per cent of the loss is often recommended, spread over portions and within four hours. 1.5 g of table salt per litre of water is particularly advisable with several sessions per day or in hot weather: the sodium ensures that the body absorbs and retains the fluid better. If only water is drunk, it dilutes the blood, urine production rises and making up the loss takes longer – more on this in the article on recovery.
Drinking too much is a real risk
The sentence «just drink a lot» is more dangerous than it sounds. Excessive drinking occurs above all in slower or less experienced endurance athletes and can lead to performance problems, gastrointestinal complaints and, in severe cases, to hyponatraemia – a sodium level below 135 mmol/l due to dilution. It often runs without symptoms but can be life-threatening.
Typically well tolerated are 0.3 to 0.8 litres per hour; around 0.8 l/h is usually the upper limit in intense endurance work, and values around 1.2 l/h are rarely well tolerated. The higher the intensity, the less fluid the body absorbs, and running sports tolerate less than cycling.
In the other direction: if dehydration arises during exercise and you drink according to thirst, losses of body mass of up to around 4 per cent are mostly without any noticeable loss of endurance. Above that, the likelihood of cramps or gastrointestinal complaints rises considerably; in less well-trained people, 2 to 3 per cent can already be limiting. Why cramps are rarely a purely electrolyte problem is shown in the article Muscle cramps.
Course tip from update Akademie: Do you want to plan drinking strategies not by gut feeling but according to sweat rate, exercise duration and performance level? The Sporternährungscoach programme at update Akademie covers hydration as a module of its own – with the weighing protocol and the assessment of sports drinks via osmolality and carbohydrate type.
Frequently asked questions about electrolytes and sports drinks
From when do I need a sports drink instead of water?
The reference value is 0.4 to 0.8 litres of sports drink extra per hour of sport; for a duration of under one hour, water is used. For most gym and class sessions, water is therefore enough.
Which minerals really belong in a sports drink?
Only sodium. It is the only mineral with a scientifically justified place in it, because it promotes rehydration; usual contents are 0.2 to 0.4 g per litre. Added vitamins, further minerals or amino acids are not necessary and can make the drink less well tolerated.
How do I mix a sports drink myself?
One litre of water or fruit tea, 30 g of sugar or fruit sugar, 50 g of maltodextrin and 1.5 g of table salt. That gives around 80 g of carbohydrate per litre with a low osmolality and a tooth-friendly pH value close to 7.
Can I drink too much during sport?
Yes. Excessive drinking can trigger gastrointestinal complaints and hyponatraemia, that is, a sodium level below 135 mmol/l caused by dilution of the blood. With confusion, headaches or nausea after long exercise, medical help belongs in the picture.
Conclusion
The shelf question can be answered briefly: under an hour water, above that 0.4 to 0.8 litres of sports drink per hour depending on intensity and heat. The only mineral with an evidenced place in it is sodium; carbohydrates sensibly sit at 30 to 90 g per litre. Mixing your own is cheaper and is kinder to tooth enamel. And because too much causes problems just as too little does, the best strategy is the one worked out individually.
