If you’ve ever cramped mid-race, felt dizzy in the heat, or hit a wall despite fuelling properly — sodium (salt) might be the missing link in your performance.
For endurance athletes like triathletes and runners, sodium isn’t just another electrolyte — it’s the key to maintaining hydration, endurance, and power output.
In this guide, we’ll break down exactly what sodium does, the different forms you’ll find in sports nutrition, how much you actually need, and how to personalise your sodium intake using a sweat test.
What Is Sodium?
Sodium is a mineral and electrolyte that helps your body regulate fluid balance, nerve transmission, and muscle contractions. It’s lost primarily through sweat, along with other electrolytes like potassium, magnesium, and calcium.
For athletes, sodium plays several key roles:
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Maintaining fluid balance: Sodium helps your body retain the water you drink, preventing dehydration.
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Supporting nerve function: It allows nerves to send signals to muscles, enabling proper contractions.
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Preventing cramps and fatigue: Low sodium disrupts muscle signalling, which can cause cramps or performance drop-offs.
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Regulating blood volume and pressure: Critical for endurance performance in hot or long events.
Without enough sodium, your blood becomes more diluted as you drink water, which can lead to hyponatremia — a dangerous drop in blood sodium levels that can cause nausea, confusion, and even collapse.
What Are the Different Forms of Sodium?
There are several chemical forms of sodium used in sports nutrition, each with different absorption rates and physiological effects. The type you use can significantly influence gut comfort, hydration efficiency, and buffering capacity.
Here’s a breakdown of the most common forms — including how much actual sodium each provides per gram:
| Sodium Form | Chemical Name | Approx. Sodium Content (mg per 1g) | Key Features |
|---|---|---|---|
| Sodium Chloride | NaCl | ~390 mg sodium per gram | The most common form of sodium (table salt). Replenishes sodium quickly but can cause gut irritation in high doses. Found in most commercial sports drinks. |
| Sodium Citrate | Na₃C₆H₅O₇ | ~270 mg sodium per gram | Buffered form that’s gentler on the stomach. Helps reduce acidity (acts as a lactate buffer), improves sodium absorption, and prevents cramps without a salty taste. |
| Sodium Bicarbonate | NaHCO₃ | ~270 mg sodium per gram | Used primarily as a performance buffer to reduce muscle acidity. Can cause bloating or GI distress if over-consumed. |
| Sodium Phosphate | Na₃PO₄ | ~330 mg sodium per gram | Supports aerobic capacity and oxygen efficiency; less relevant for hydration but sometimes used in pre-event loading. |
In Summary
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Sodium Chloride provides the most sodium by weight but is harsher on digestion.
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Sodium Citrate offers smoother absorption, better buffering, and less GI discomfort — making it ideal for long-course triathlon, marathon, and hot-weather events.
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Sodium Bicarbonate can be useful for short, high-intensity events but must be dosed carefully.
Organic Performance Electrolytes use Australian Pink Lake Salt a form of Sodium Chloride. Also available is our Sodium Citrate, which can be added to the our Electrolytes when the intensity is high or the conditions are hot! Combined athletes can take advantage of optimal absorption, reduced gut stress, and superior endurance support.
Sodium Chloride vs Sodium Citrate
Both Sodium Chloride and Sodium Citrate deliver sodium, but they act differently once ingested.
Sodium Chloride
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Found in table salt and most commercial sports drinks.
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Absorbed quickly but can cause stomach irritation if taken in high doses.
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Does not buffer acidity — meaning it doesn’t help reduce the “burn” from lactate buildup.
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Can contribute to a salty aftertaste in gels and drinks.
Sodium Citrate
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A gentler, buffered form of sodium that reduces gastrointestinal discomfort.
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Helps regulate blood pH by reducing acidity during endurance efforts.
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Improves sodium absorption without the same risk of bloating or gut upset.
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Provides lactate-buffering effects, delaying fatigue during long or hot events.
What Factors Influence Sodium Requirements?
Every athlete’s sodium needs are unique. Several factors influence how much sodium you lose and how much you’ll need to replace:
1. Sweat Rate
The more you sweat, the more sodium you lose. Some athletes lose 500 mg of sodium per litre of sweat, while others lose over 2,000 mg/L.
2. Sweat Sodium Concentration
Sweat composition varies by genetics, diet, and acclimation. Heavier “salty sweaters” often see white streaks on their clothing or feel salt crystals on their skin after long sessions.
3. Climate and Temperature
Hot and humid conditions dramatically increase sodium and fluid losses. Athletes training in these environments need more frequent electrolyte replacement.
4. Duration and Intensity
Longer, harder sessions deplete sodium more rapidly. Triathletes and marathoners often need aggressive electrolyte strategies compared to recreational runners.
5. Diet
Athletes on low-sodium or “clean eating” diets may start races with lower sodium stores. A moderate sodium intake before training can improve hydration status.
How Much Sodium Do You Need During Training & Racing?
There’s no one-size-fits-all answer, but here are general guidelines supported by research and practical endurance experience:
| Training Duration | Sodium Target (mg/hr) | Carb & Fluid Strategy |
|---|---|---|
| <1 hour | 200–400 mg | Water or light electrolytes |
| 1–2 hours | 400–800 mg | 30–60g carbs/hr + electrolytes |
| 2–4 hours | 800–1,000 mg | 60–90g carbs/hr + electrolytes |
| 4+ hours (Ironman, Ultra) | 1,000–1,500+ mg | 90–120g carbs/hr + high sodium fluids |
During Ironman and marathon events, aim for 1,000–1,500 mg of sodium per hour, depending on sweat rate and conditions.
Pro Tip: Split your intake between drink mixes, gels, and electrolyte capsules to avoid overloading your stomach.
How to Conduct a Sweat Test
A sweat test helps you identify your personal sodium and fluid loss rate. Here’s a simple version you can do at home:
Step 1: Weigh Yourself
Weigh yourself (in kilograms) before a 1-hour workout in similar race conditions. Do this without clothes or in minimal clothing.
Step 2: Record Fluid Intake
Track exactly how much water or electrolyte drink you consume during the session.
Step 3: Weigh Yourself After
Weigh yourself again immediately post-workout, towel-dried, wearing the same clothing.
Step 4: Calculate Sweat Rate
Sweat loss (L/hour) = (Pre-weight – Post-weight) + Fluid intake (L)
Example:
Pre = 70.0 kg
Post = 69.0 kg
Fluids = 0.5 L
→ Sweat rate = (1.0 + 0.5) = 1.5 L/hour
Step 5: Estimate Sodium Loss
Multiply your sweat rate (L/hr) by your estimated sodium concentration.
If you lose ~1,000 mg/L and sweat 1.5 L/hour, that’s 1,500 mg sodium/hour.
From here, you can build your personalised electrolyte plan. Noting without a sweat test this information is unavailable, athletes can trial different sodium intake during training to see what works best for them.
Putting It All Together: Example Sodium Strategy
For a triathlete racing in warm conditions:
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Pre-Race: Add 500–1,000 mg sodium + 500 ml water about 60 minutes before start
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Bike Leg: Include 1,000–1,200 mg sodium per hour in your drink mix
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Run Leg: Continue 800–1,000 mg sodium/hr via electrolyte flasks or gels
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Post-Race: Replenish 1,000–2,000 mg sodium + 1.5x fluids lost
Closing Thoughts: The Sodium Advantage
Sodium is more than just salt — it’s your endurance lifeline. For triathletes and runners, getting sodium balance right means:
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Improved hydration
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Better energy and focus
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Fewer cramps and less fatigue
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Stronger performance in heat
By understanding your sweat rate, using buffered forms like Sodium Citrate, and consistently topping up with electrolytes, you can maintain power output from start to finish.