Hydration Beyond Water: Electrolytes, Performance, and What Actually Matters

Drinking more water is not always the answer. Electrolyte balance matters as much as fluid volume for training performance and health.

By Dr Matt Walley, PhDPublished 6 November 2025Last reviewed 21 April 2026

The "drink more water" line is so common it has lost meaning. Hydration is not just about water volume. It is about the balance of water and electrolytes that maintains cellular function, nerve signalling, muscle contraction, and blood pressure. Drinking large volumes of plain water without adequate electrolytes can backfire, diluting blood sodium and impairing performance.

Electrolyte roles

Sodium is the primary extracellular electrolyte and the one lost in greatest quantity through sweat. It maintains fluid balance, supports nerve impulse transmission, and is needed for muscle contraction. Most athletes need 500 to 1,500mg of additional sodium during prolonged exercise. Potassium is the primary intracellular electrolyte, working with sodium to maintain cellular fluid balance and supporting cardiac function. Magnesium runs over 300 enzymatic reactions, including ATP production, muscle relaxation, and nerve function.

Hyponatremia risk

Hyponatremia, dangerously low blood sodium, happens when excessive water intake dilutes sodium below safe levels. The risk is real during prolonged endurance events where athletes drink large volumes of plain water without sodium replacement. Symptoms: confusion, nausea, headache, and in severe cases, seizures. Prevention is straightforward. Include sodium in your hydration strategy during prolonged exercise.

Practical guidelines

For training under 60 minutes in moderate conditions, plain water is fine. For sessions over 60 minutes or in hot conditions, add electrolytes. A simple approach: 500ml of water with a pinch of salt and a squeeze of citrus per hour of training. Commercial electrolyte products work, but check the sodium content. Many contain too little sodium to matter.

Frequently asked questions

How much water should I drink daily? A general guideline is 35ml per kilogram of body weight, adjusted upward for training, heat, and altitude. Urine colour (pale yellow) is a practical indicator of adequate hydration.

Are sports drinks necessary? For most recreational training, no. For endurance sessions over 60 to 90 minutes or in hot conditions, the electrolyte and carbohydrate combination in sports drinks gives a real performance benefit.

Hydration is personalised too. Our programmes account for your training load and environment. Explore coaching and learn about recovery nutrition.

Quick answers

Can drinking too much water be bad for you?

Yes. Excessive water intake without sodium replacement dilutes blood sodium levels, a condition called hyponatremia. Symptoms include confusion, nausea, headache, and in severe cases seizures. The risk rises during prolonged endurance events where athletes consume large volumes of plain water. The fix is straightforward. Include sodium in your hydration strategy whenever sessions exceed 60 minutes or conditions are hot.

Do I need electrolytes for a one hour gym session?

For most training under 60 minutes in moderate conditions, plain water is sufficient. Electrolyte losses during shorter sessions are modest and replaced through normal meals. Add electrolytes when sessions exceed 60 minutes, when training in hot or humid conditions, or when you finish sessions visibly salt-stained. Context matters more than blanket rules.

How much sodium do I need during long training sessions?

Most athletes need 500 to 1,500mg of additional sodium per hour during prolonged exercise. Individual sweat rates and sodium concentrations vary considerably. A practical starting point is 500ml of water with a pinch of salt and a squeeze of citrus per hour. Many commercial electrolyte products contain insufficient sodium to matter. Check the label before assuming a product is doing the job.

How much water should I drink each day in New Zealand conditions?

A general guideline is 35ml per kilogram of body weight daily, adjusted upward for training load, heat, and altitude. A 75kg person starts around 2.6 litres. New Zealand summers and humid northern conditions push requirements higher. Pale yellow urine is a practical indicator of adequate hydration. Dark yellow signals you are behind. Clear urine all day suggests you are overdoing plain water.

What do magnesium and potassium actually do for performance?

Potassium is the primary intracellular electrolyte, working with sodium to maintain cellular fluid balance and supporting cardiac function. Magnesium participates in over 300 enzymatic reactions including ATP production, muscle relaxation, and nerve signalling. Deficiencies in either impair performance and recovery. Whole foods cover most needs. Leafy greens, nuts, seeds, and dairy supply magnesium. Fruit, potatoes, and legumes supply potassium.

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Author

Dr Matt Walley

PhD, Founder of Inception Nutrition

Over 1,380 clients. Twenty-two years of applied practice. PhD research informing every framework, scan, and decision.

More about Dr Walley

The content of this article is for general informational and educational purposes only. It does not constitute medical advice and should not replace consultation with a qualified health professional. Outcomes vary based on individual physiology, training history, and adherence. If you have an existing medical condition, take prescription medication, or are pregnant or breastfeeding, consult your GP or specialist before making nutrition or training changes.