Fueling Performance: The Critical Role of Carbohydrates Hydration and Sodium for Endurance Athletes

Endurance athletes push their bodies to the limit, often for hours at a time. To sustain high performance, they need more than just training and determination. What they eat and drink before, during, and after exercise plays a crucial role in how well they perform and recover. Among the many nutritional factors, three stand out as essential levers for endurance success: carbohydrates, fluid intake, and sodium. Understanding how these elements work together can help athletes avoid fatigue, maintain strength, and finish strong.

Endurance cyclist hydrating during training

Endurance athletes must balance fuel and hydration to maintain performance during long training sessions and races.

Carbohydrates: The Primary Fuel for High-Intensity Efforts

Carbohydrates are the body’s preferred energy source during intense exercise. When you run, bike, swim or exercise at high intensity, your muscles rely heavily on glycogen, the stored form of carbohydrates, to keep going. Unlike fats, which burn slower, carbohydrates provide quick energy that supports bursts of speed, climbs, and sustained effort.

Why Carbohydrates Matter

• Fast energy release: Carbohydrates break down into glucose, which muscles use immediately.

• Delay fatigue: Maintaining glycogen stores helps prevent the “bonk”, "hitting the wall" or sudden energy crash.

• Support brain function: Glucose fuels the brain, helping maintain focus and coordination.

  
  

How Much Carbohydrate Do Endurance Athletes Need?

The amount depends on training intensity and duration:

• For moderate training (1 hour/day), aim for 5-7 grams per kilogram of body weight daily.

• For intense training (1-3 hours/day), increase to 7-10 grams per kilogram.

• For extreme endurance events (over 4 hours), 10-12 grams per kilogram may be necessary.

  
  

Practical Tips for Carbohydrate Intake

• Before exercise: Eat a carbohydrate-rich meal 3-4 hours before activity. Examples include oatmeal with fruit, rice with lean protein, or a pasta dish.

• During exercise: Consume 30-60 grams of carbohydrates per hour for events lasting longer than 60 minutes. Sports drinks, gels, bananas, or energy bars work well.

• After exercise: Replenish glycogen with a carb-rich snack or meal within 30 minutes of finishing. Chocolate milk, smoothies, or a sandwich are good options.

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  The graph illustrates fat and carbohydrate combustion rates at different exercise intensities. Green and orange curves show fat and carbohydrate utilisation, respectively. The "FatMax zone" marks the optimal intensity for peak fat burning, while the orange shaded area indicates maximum carbohydrate intake.

  
  
  
  

Fluid: How Proper Hydration Supports Blood Volume and Cooling

Staying hydrated is vital for endurance athletes. Water makes up about 60% of the body and plays a key role in regulating temperature and transporting nutrients. During exercise, sweating cools the body but also causes fluid loss. If not replaced, dehydration reduces blood volume, making the heart work harder and impairing performance.

Effects of Dehydration on Performance

• Reduced blood flow to muscles and skin

• Increased heart rate and perceived effort

• Impaired temperature regulation leading to overheating

• Decreased endurance and strength

  
  

How Much Fluid Should Athletes Drink?

Fluid needs vary by sweat rate, temperature, and exercise intensity. A general guideline is:

• Drink 400-600 ml (13-20 oz) of fluid 2-3 hours before exercise.

• During exercise, aim to replace 80-100% of sweat losses. This often means drinking 150-350 ml (5-12 oz) every 15-20 minutes.

• After exercise, consume 1.5 times the fluid lost during activity to fully rehydrate.

  
  

Practical Hydration Tips

• Test sweat rate: Weigh yourself before and after training to estimate fluid loss, check blog on how to do this.

• Use flavoured drinks: They encourage drinking more and provide carbohydrates.

• Avoid over-hydration: Drinking too much water without electrolytes can cause hyponatremia, a dangerous drop in blood sodium.

  
  
  
  

Sodium: The Electrolyte That Maintains Fluid Balance

Sodium is an essential electrolyte lost through sweat. It helps regulate fluid balance, nerve function, and muscle contractions. When sodium levels drop, athletes risk cramping, dizziness, and poor performance.

Why Sodium Is Critical for Endurance Athletes

• Maintains blood volume and pressure

• Supports nerve signals for muscle movement

• Prevents hyponatremia during prolonged sweating

  
  

How Much Sodium Do Athletes Lose?

Sweat sodium concentration varies widely, from 300 to 1,500 mg per litre of sweat and is very individual. Heavy sweaters or those exercising in hot conditions lose more sodium and need to replace it accordingly.

Practical Sodium Replacement Strategies

• Use sports drinks containing sodium during exercise.

• Include salty snacks like pretzels or salted nuts during long events.

• Consider sodium supplements or electrolyte tablets for races lasting over 3 hours.

• Monitor symptoms like muscle cramps or nausea as signs of sodium imbalance.

• Get a sweat analysis

Putting It All Together: Fuelling and Hydrating for Training and Race Day

Balancing carbohydrates, fluid, and sodium intake is key to maximizing endurance performance. Here are some actionable steps athletes can take:

• Plan meals and snacks around carbohydrate needs, focusing on quality sources like whole grains, fruits, and vegetables.

• Practice hydration strategies during training to find what works best for your sweat rate and preferences.

• Include sodium in your hydration plan, especially for long or hot sessions.

• Use a combination of fluids and solid foods during long events to maintain energy and electrolyte balance.

• Listen to your body and adjust intake based on thirst, sweat, and performance.