The Best Hydration Strategy for Training and Competition

The Best Hydration Strategy for Training and Competition – a Guest Post by Juli Brüning (Part 3/3)

For optimal race performance, two key factors play a crucial role in nutrition: energy intake and hydration strategy. The latter can be further divided into fluid and electrolyte/sodium intake, both of which depend heavily on individual needs. Essentially, energy, fluid, and sodium intake form the three pillars of race nutrition.

Figure 1: The three pillars of race nutrition. Adapted from Precision Hydration Ltd.

While all three pillars are important for both training and competition, preparing a hydration strategy for race day is more specific. Both require a certain level of understanding and planning. The foundation for this is determining—or at least estimating—your individual sweat sodium concentration and sweat rate.

From Theory to Practice: Just like carbohydrate intake, achieving optimal fluid consumption during a race can be quite challenging depending on the situation. This can be due to logistical reasons or limitations of the digestive system. How much fluid the stomach can handle and how quickly the body can absorb it is highly individual. Both can be trained, and the "Train the Gut" principle applies equally to consuming higher amounts of carbohydrates per hour as well as maintaining adequate fluid intake. ¹

Guidelines for Hydration Strategy in Training

1. Before Training:

Laying the Foundation: Generally, drinking according to thirst throughout the day is enough to start a training session well-hydrated. If there’s a suspicion of slight dehydration, a strategy called "Pre-Loading" can be applied before the session begins.

Pre-Loading Strategies help the body temporarily retain more water and quickly reach a balanced hydration status—or even store more water than needed for proper fluid balance (hyperhydration). This provides the body with a larger reservoir of fluid for sweating, delaying the onset of dehydration during exertion. Studies show the effectiveness of pre-hydration (hyperhydration) strategies, especially under hot conditions and heat stress, to enhance endurance performance². A strong electrolyte drink adds an "extra boost" of fluid for the body's cooling mechanism.

Pre-Loading for Intense Sessions: Pre-loading isn’t necessary before every training session. It’s a strategy that can be particularly useful:

before especially long and intense training sessions
in particularly warm conditions
when high sweat losses are expected
when fluids/drinks are limited or not easily accessible during the session

Recommendation: Drink a strong electrolyte beverage with ~750 mg of sodium in 500 ml (e.g., 1x tablet of PH1500) about 90–45 minutes before starting your training session.

Note: The pre-loading recommendation is universal and not dependent on individual sweat sodium concentrations during exercise.

2. During Training (under 1 hour)

Fluid Intake: If you start your session well-hydrated, you typically don’t need to drink during short workouts. However, when training in the heat or in humid conditions, it can still be a good idea to have a drink on hand.

Electrolyte Intake: Even for the "saltiest sweaters" among us, it’s highly unlikely that you need to replace sodium during a short training session.

3. During Training (between 1–2 hours)

1–2 hours represents a kind of "gray zone" for hydration, as the amount of fluids and electrolytes needed depends on your sweat rate and how salty your sweat is.

Fluid & Electrolyte Intake: Most people can tolerate a certain degree of dehydration without a significant drop in performance. Drinking according to thirst may still be sufficient in this range.

For "heavy sweaters" and "salty sweaters": As dehydration and/or intensity increase, the body's thirst signals become less reliable. Those who sweat heavily and with high salt content need a more strategic approach.

Electrolyte Intake: Should match the relative sodium concentration of your individual sweat profile.
Fluid Intake: The amount of fluid should be adjusted according to your sweat rate.

Example:

Individual sweat sodium concentration: 950 mg/L.
Sweat rate: Moderate at 750 ml/h.
Recommendation: For 90–120 minutes, about 500 ml of fluid is sufficient. With a relative sodium concentration of 950 mg/L, this means a sodium intake of 475 mg for the 500 ml (475 mg/500 ml = 950 mg/L).

4. During Training (2.5+ hours)

Training sessions lasting more than 2 hours (especially in hot and/or humid conditions) require proactive fluid intake to maintain optimal performance.

Fluid Intake: ~500 ml per hour is a good starting point for fluid intake, which can be adjusted up or down as needed.

Electrolyte Intake: The majority of fluid intake should include electrolytes at the same relative sodium concentration as the individual sweat sodium concentration.

The sweat and sodium losses don’t need to be replaced 100%, but dehydration exceeding 2-4% of body weight over the duration of the session should be avoided.

For very low sweat and sodium losses: Fluid and electrolyte intake should still be relatively low.
For "heavy sweaters" and "salty sweaters": Up to 1,500 mg/L and >500–750 ml per hour may be required.

Recommendation: Start experimenting with your training based on your individual sweat sodium concentration and sweat rate information. A craving for salty foods is a sign of a low sodium level, while craving water indicates too high a sodium level.

5. After Training - Rehydration:

General Rehydration: It’s normal to be slightly dehydrated at the end of a training session. In most cases, compensating for electrolyte and fluid losses through the salt intake in daily foods and drinks is sufficient. The general recommendation is to consume 1.5 times (150%) the body weight lost in fluids to return to a balanced hydration state.

Specific Rehydration: In some cases, it’s beneficial to proactively rehydrate according to a plan. This applies to athletes who experience:

Consecutive training sessions
Particularly high sweat losses during the session
Late training sessions with limited time to eat and drink afterward

Proactive Rehydration: Consume 500 ml of a strong electrolyte drink (750 mg sodium) within the first 30 minutes after the training session (e.g., 1x PH1500 tablet). In extreme cases, up to 1 L with 1,500 mg sodium in the first 30 minutes to 2 hours.

Guideline for Hydration Strategy in Races

Before the Race

Shorter Distances and Duration: The focus is mainly on starting optimally hydrated.

Recommendation: Pre-loading strategy as in training, but starting a little earlier.
Pre-Loading: A strong electrolyte drink with 750 mg in 500 ml (e.g., 1x PH1500 tablet in 500 ml) the evening before the race and on the morning of the race, about 60-90 minutes prior, ensures optimal hydration at race start.

Longer Distances and Duration: Same pre-loading strategy, with additional focus on hydration during the race.

During the Race

For Race Duration of 1-2 Hours:

Fluid and Electrolyte Intake: Based on sweat rate and sweat sodium concentration. The recommendation is similar to that from training nutrition.

For Race Duration of 2.5+ Hours:

Individually planned hydration strategy required.
“Hydration Equation”: Sweat sodium concentration, sweat rate, and race duration determine the total sweat and sodium losses during the race.
Recommendation: Plan hourly fluid intake to ensure no more than 2-4% body weight dehydration at the end of the race.

Figure 2: Hydration Equation. Adapted from Precision Hydration Ltd.

Different start times and race durations throughout the day and night can significantly change the environmental conditions. Likewise, varying intensities depending on terrain and elevation profiles, along with sudden weather changes in the mountains, may require flexible fluid and sodium intake.

The Importance of RELATIVE Sodium Concentration

While fluid intake per hour is flexible and depends on changes in the sweat rate, the relative sodium concentration always remains the same. Higher sweat losses lead to greater fluid needs, while lower sweat rates require less fluid, but both always maintain the same relative sodium concentration.

For those who don’t know their sweat sodium concentration precisely, they can categorize themselves into a rough ‘saltiness’ range (see the key role of sodium) and adjust sodium intake accordingly: Slightly salty = 500mg/L, moderately salty = 1,000 mg/L, or very salty = 1,500 mg/L. For most athletes, it will be sufficient to select a product with the appropriate electrolyte strength based on their category, without knowing their exact sweat sodium concentration. (Why and for whom a sweat test is still useful, see Part 1).

Practical Application

How the appropriate sodium intake is achieved is highly individual. It depends on whether liquid carbohydrates are used via sports drinks for energy, or if carbohydrate intake remains largely independent of fluid intake. Depending on the sodium content of preferred sports drinks, sodium intake can be adjusted with additional electrolyte tablets or salt capsules.

Alternatively, one can choose an electrolyte drink with the appropriate sodium content from the start, and carbohydrate intake can primarily come from gels, chews, bars, or solid food with little or no added electrolytes.

Sodium Content - Comparison of Gels

Sodium Content - Comparison of Drink Mix 500ml

Sodium Content - Comparison of Electrolyte Mixes & Supplements

Conclusion: No ‘One-Size-Fits-All’ - Each Path is Individual

Many athletes, many strategies: Although the scientific principles are the same for everyone, each race nutrition plan is unique. Whether fluid, sodium, or carbohydrates – everyone must find their own way that works best for them. The foundational knowledge provides the starting point to develop a personal strategy. From there, it’s about testing a lot during training, adjusting for specific race demands, and properly training the digestive system.

This article is not medical advice regarding energy, sodium, or fluid intake. It does not replace consulting a doctor or other healthcare professional before making changes to your diet, supplementation, or nutrition strategy.

¹ Jeukendrup AE. Training the Gut for Athletes. Sports Med. 2017 Mar;47(Suppl 1):101-110. doi: 10.1007/s40279-017-0690
6. PMID: 28332114; PMCID: PMC5371619.

² Convit L, Orellana L, Périard JD, Carr AJ, Warmington S, Beaugeois M, Abraham A, Snipe RMJ. Sodium Hyperhydration Improves Performance With No Change in Thermal and Cardiovascular Strain in Female Cyclists Exercising in the Heat Across the Menstrual Cycle. Int J Sport Nutr Exerc Metab. 2025 Jan 23;35(2):99-111. doi: 10.1123/ijsnem.2024-0125. PMID: 39591960.

List of Figures:

Title Image: Runner, Pexels.

Figure 1: The 3 Pillars of Race Nutrition.

Figure 2: Hydration Equation.

Juli Brüning

Juli is a nutrition scientist (M.Sc.), performance nutritionist, and ultra trail runner for the Craft Elite Run Team Germany. She supports athletes with all sport- and nutrition-related topics and works as a sweat test center and athlete support for Precision Fuel and Hydration. The physiological processes of metabolism and female-specific physiology are the core themes of her work.