Electrolytes for Endurance: When Water Alone Isn’t Enough

About the author
EnduranceVitals Editorial Team – sports nutrition writers who research every product in our range. This article is informational and not medical advice.

Long runs, hot rides and back-to-back training days do more than empty your glycogen stores. Every litre of sweat carries sodium, potassium and magnesium out with it, and plain water cannot put them back. This guide explains which electrolytes matter for endurance, when a supplement is actually worth taking, and how to choose one from our range.

Key takeaways

• Sweat loses sodium above all, plus potassium, magnesium and calcium. Water alone does not replace them.
• Sessions over 60 to 90 minutes, hot conditions and heavy sweaters are when electrolyte supplements earn their place.
• Sodium helps your body hold on to fluid; magnesium contributes to normal muscle function and electrolyte balance.
• Take electrolytes before and during long efforts, and keep magnesium as a daily habit.
• Match the product to the job: tablets for training days, magnesium capsules for everyday cover.

Why electrolytes matter for endurance

Electrolytes are minerals that carry an electrical charge. They regulate fluid balance, nerve signalling and muscle contraction, which is exactly what you ask of your body for hours on end. Sweat rates of 0.5 to 2 litres per hour are common in endurance sport, and each litre can take several hundred milligrams of sodium with it. If you replace that sweat with water only, blood sodium gradually dilutes. The result is the familiar late-session fade: heavy legs, a drop in power and, for some people, cramping or a headache.

Magnesium matters too. It contributes to normal muscle function, normal energy-yielding metabolism and the reduction of tiredness and fatigue, and hard training raises the amount you lose.

Electrolyte supplements in our range

OstroVit Electrolytes (90 tablets)

OstroVit Electrolytes (90 tablets) gives you the key minerals you lose in sweat in a simple tablet form. It is easy to dose on the move, stores well in a race belt or bike bag, and does not need a bottle of flavoured powder to work.

Magnesium Citrate 400 mg + B6

OstroVit Magnesium Citrate 400 mg + B6 (90 tablets) is the daily workhorse. Citrate is a well-absorbed form, and vitamin B6 contributes to normal energy-yielding metabolism and the reduction of tiredness. It suits high training loads and anyone who notices twitches or cramps after big weeks.

Magnesium Glycinate

OstroVit Magnesium Glycinate (90 capsules) is the gentle option. Glycinate is easy on the stomach and a popular evening choice, supporting normal muscle function and normal functioning of the nervous system when the day winds down.

Pre-Workout 240 g

For hard intervals and race days, OstroVit Pre-Workout (240 g) adds the kick. Pair it with electrolytes in hot conditions rather than relying on it alone, and keep an eye on your total caffeine for the day.

Which electrolyte supplement should you choose?

• Long sessions, heat or heavy sweating: Electrolytes tablets before and during.
• Daily cover during heavy training blocks: Magnesium Citrate + B6 with a meal.
• Evening recovery or a sensitive stomach: Magnesium Glycinate before bed.
• Race day or hard intervals: Pre-Workout, plus electrolytes if it is warm.

How and when to take electrolytes

Before: take one serving with 300 to 500 ml of water 30 to 60 minutes before a long or hot session. During: for efforts over 90 minutes, top up roughly every 45 to 60 minutes, always alongside water rather than instead of it. After: a common guideline is to drink about 1.5 litres of fluid for every kilogram of body weight lost, with some sodium in it, then take your magnesium with the evening meal.

For short, easy sessions under an hour, water is usually enough. If you follow a low-sodium diet on medical advice, speak to your doctor before adding electrolytes.