When electrolytes matter during training

General information, not medical advice. If you have symptoms, discuss them with your GP or a dietitian.

When electrolytes are useful depends on how long you train, on the heat and on how much you sweat. You often hear that you should always drink two litres and add electrolytes. For most recreational athletes that is overstated: context matters more than a fixed litre count with a measured dose of powder.

When water is enough

Nancy Clark writes in a practice article on the American College of Sports Medicine (ACSM) site from July 2025 that most fitness exercisers who train for less than 60 to 90 minutes a day in normal weather are unlikely to become dehydrated or depleted of electrolytes. That is not an ACSM position stand, but an accessible practice summary. Think of an hour of strength training or zone 2, an easy endurance pace where you can still talk comfortably, in a mild training room or cool outdoor air.

The National Athletic Trainers’ Association (NATA), the US professional body for athletic trainers, summarises in its 2017 position statement that hydration is best judged with a combination of thirst, urine colour and body weight. Light yellow urine usually points to a reasonable balance. On long or hot sessions, weighing before and after shows how much fluid you lost.

The European Food Safety Authority (EFSA) treats 2.0 litres a day for women and 2.5 litres for men as an adequate total water intake for adults, drinks and food together, under moderate temperature and activity. That is a population reference value, not a drinking protocol for sport.

When electrolytes become useful

Electrolytes, in practice mainly sodium, matter more with longer effort, heat, tournament days or if you sweat heavily yourself. The ACSM position stand by Sawka and colleagues (2007) aims to avoid body-mass loss of more than 2 percent during exercise. Weighing before and after a long session shows how much fluid you lost. Weight gain during exercise points, according to NATA and Hew-Butler, to drinking too much.

In exercise lasting about an hour or more, drinks with electrolytes and carbohydrates can under certain circumstances benefit more than water alone, ACSM wrote in 2007. The German working group on sports nutrition of the DGE (Mosler and colleagues, 2020) sees carbohydrate–sodium drinks mainly beyond one and a half hours, and sodium during exercise mainly with very high sweat loss and duration above two hours. Those thresholds should not be mixed up with Clark’s 60 to 90 minutes.

Anyone who, during long efforts such as a marathon or triathlon, drinks far more than thirst asks for risks a too-low blood sodium level (hyponatraemia). The international consensus by Hew-Butler and colleagues (2015) therefore advises drinking to thirst. The advice “always drink before you are thirsty” is seen as outdated because it encouraged overdrinking. Sports drinks are still hypotonic relative to blood plasma: you can overdrink those too.

Commercial electrolyte powders and tablets are, according to Clark, often mainly about convenience, not a unique necessity. Salty food plus water can cover the same need. For HIIT, short hard intervals with rest in between, of half an hour in a well-ventilated room, water is enough for most people.

Practical around training

Start from duration, climate and sweat, not from a fixed litre target. Combine thirst, urine colour and, on long or hot sessions, your weight. Do not drink until you gain weight during a long event. Afterwards, an ordinary meal and water often replenish fluids and energy until the next day, especially if no new hard session follows within 24 hours; more on that window in what counts in the first 24 hours after training.

If you still buy a powder or sports drink, first read how to read a supplement label: how much sodium and sugar per portion, and whether the claim fits your training. Individual sweat losses vary widely; a fixed sodium-intake schedule does not belong in a general article.