Hydration for Runners

Why Hydration is Essential for Runners

Proper hydration supports multiple physiological processes critical for running performance:

Temperature Regulation: During running, your body generates heat, and sweating is the primary mechanism to cool down. If you're dehydrated, this cooling process becomes less efficient, increasing the risk of heat exhaustion or heat stroke (Casa et al., 2000).
Muscle Function: Muscles need water to function optimally. Dehydration impairs muscle contraction, making cramps and fatigue more likely, and increasing the risk of strains (Klein et al., 2007). Hydration ensures that muscles remain flexible and responsive.
Recovery and Injury Prevention: After running, hydration aids nutrient transport and waste removal, which is essential for muscle repair and recovery. Inadequate hydration can result in prolonged recovery times and increased susceptibility to injuries.

Hydration Strategies

Before the Run: Aim to drink 500 ml of water 2–3 hours before running. This gives your body time to absorb and distribute the fluid. If you’re planning a long run (more than 60 minutes), adding electrolytes to your pre-run hydration can help prepare your body to maintain fluid balance during the activity.

During the Run:

Short Runs (Under 60 minutes): Water is generally sufficient for hydration during shorter runs. Aim to drink small sips every 15-20 minutes.
Long Runs (60 minutes or more): For runs lasting longer than an hour, you’ll need more than just water. Sweat leads to the loss of electrolytes like sodium, potassium, and magnesium, which need to be replaced to avoid muscle cramps and fatigue. Sports drinks or electrolyte tablets are good options for replenishment. Aim to drink 150-250 ml of fluid every 20 minutes, depending on your sweat rate and environmental conditions.

Post-run: Hydrate immediately after your run to optimise recovery. Aim to drink 500–600 ml of water or an electrolyte drink within 30 minutes of finishing your run. To replace fluid lost during longer runs, follow the 1.5x fluid replacement rule. For example, if you lost 0.5 kg of body weight during your run, you should replace 750 ml of fluid. If you’ve had a particularly challenging run, a recovery drink containing both carbohydrates and protein may also help replenish glycogen stores and support muscle repair.

The Role of Electrolytes

Electrolytes are minerals that carry an electrical charge and are essential for muscle function, nerve transmission, and maintaining fluid balance. As a runner, you primarily need to focus on replacing the following electrolytes:

Sodium (Na): Sodium is the most important electrolyte for runners because it helps maintain fluid balance and regulates blood pressure. Sweating leads to sodium loss, which is why it’s especially important to replace during longer runs (Maughan & Shirreffs, 2004).
Potassium (K): Potassium helps balance fluid levels inside cells and supports proper muscle function. Low potassium can result in muscle cramps and weakness (Gleeson, 2006).
Magnesium (Mg): Magnesium aids in muscle relaxation and energy production. Deficiency can contribute to muscle cramps, fatigue, and decreased performance (Zhou et al., 2017).
Calcium (Ca): Calcium plays a key role in muscle contraction and nerve function.

How to Replace Electrolytes

There are a few ways to replace lost electrolytes during a run:

Sports Drinks: Most sports drinks contain a combination of water, sugar, and electrolytes. Choose drinks that offer a 4-8% carbohydrate concentration and about 200-400 mg of sodium per 500 ml for optimal hydration and energy during long runs.
Electrolyte Tablets or Powders: These provide a low-calorie option and allow you to control your electrolyte intake. Electrolyte tablets dissolve easily in water and typically contain sodium, potassium, magnesium, and calcium.
Foods: If you prefer a natural option, foods like bananas, salted nuts, and dairy products are good sources of electrolytes. Coconut water is also a natural alternative rich in potassium and sodium, though it may lack sufficient sodium to fully replace electrolytes lost during intense activity.

General Hydration Tips

Proper hydration isn’t just important during exercise—it’s essential throughout the day. Here are some general hydration tips for optimal performance:
Hydrate Throughout the Day: Aim to drink 2-3 litres of water daily, adjusting based on your activity level. For runners, especially those training regularly, aim for 2.5–3.5 litres daily. Keep a water bottle handy throughout the day to make it easy to drink consistently.
Monitor Your Urine: The colour of your urine is a great indicator of your hydration status. If your urine is light yellow or straw-coloured, you’re well-hydrated. Darker urine, like amber or brown, indicates dehydration.
Thirst is a Late Signal: By the time you feel thirsty, you’re already mildly dehydrated. Stay ahead of thirst by drinking small amounts of water regularly throughout the day.
Avoid Overhydration: While staying hydrated is crucial, drinking too much water without replacing electrolytes can lead to hyponatremia (low sodium), which is a rare but serious condition. It’s important to balance fluid intake with electrolytes, especially during long runs or races.

Hydration and Weather

Weather conditions significantly impact your hydration needs:

Cold Weather: You might not feel thirsty during colder months, but your body still loses moisture through sweating and breathing. Even in winter, maintain your hydration routine and drink regularly throughout your run.
Hot and Humid Weather: In warmer weather, fluid loss through sweat increases. To avoid dehydration and heat-related issues, increase both your fluid and electrolyte intake. If possible, run during cooler times of the day, such as early mornings or evenings.

Final Thoughts

Hydration is a cornerstone of running performance, recovery, and injury prevention. Understanding your fluid needs and tailoring your hydration strategy based on your run duration, environmental conditions, and sweat rate will help you perform at your best. Remember, hydration is an ongoing process that involves not just drinking water but balancing electrolytes, monitoring fluid loss, and maintaining consistency. By applying these principles, you’ll be able to optimise your performance and stay injury-free.

References

Casa, D. J., Armstrong, L. E., Hillman, S. K., et al. (2000). National Athletic Trainers’ Association Position Statement: Fluid Replacement for Athletes. Journal of Athletic Training, 35(2), 212–224.

Gleeson, M. (2006). Immune function in sport and exercise. Journal of Sports Sciences, 24(7), 781-793.

Maughan, R. J., & Shirreffs, S. M. (2004). Hydration and performance during sport. Journal of Sports Sciences, 22(7), 711-720.

Klein, A. J., et al. (2007). The role of dehydration in exercise-related muscle cramps. Current Sports Medicine Reports, 6(4), 184–189.

Zhou, S., et al. (2017). Magnesium supplementation and physical performance in athletes. Journal of Sports Science and Medicine, 16(3), 296–306.