According to you, what are the qualities an athlete should have? What routine must an athlete have? Well, most of the answers would be performance, healthy diet, training, discipline, and consistency. Even most of the endurance athletes, when they think from the perspective of performance, focus on mileage, pace, nutrition, and training. Yet many of them forgot that the most important factor in an athlete's life is hydration. Water isn’t about preventing us from thirst, but it’s the foundation to build stamina, decision-making, and mental clarity.

Science has repeatedly warned about the effects of dehydration. It doesn’t just affect physical health but also has an impact on mental health. For endurance athletes, this connection can be the difference between finishing strong and hitting the wall.

A landmark study published in the Journal of Applied Physiology revealed that losing just 2% of body weight through sweat can decrease cognitive functions. Thereby, it can affect attention span, short-term memory, and sudden reaction. This might sound like a small number, and most people ignore it. But for a 70 kg athlete, that's just 1.4 litres of fluid loss. This can happen easily in endurance athletes during a long-distance run, especially in warm conditions. The brain is about 75% water, and even a small imbalance can affect the brain's neural system directly.

At a neurochemical level, dehydration releases cortisol, also known as a stress hormone. Increased cortisol not only makes athletes feel mentally tired, but it also disrupts the mechanism of the prefrontal cortex. The prefrontal cortex is an important region in the brain that is responsible for decision-making and focus. That’s why most marathon runners who are dehydrated often experience a sense of mental fog. They also struggle to maintain pace, strategy, and respond to the signals from their body. It's not only about physical tiredness, it's about the brain losing its sharpness.

A 2020 review in Sports Medicine highlighted how hydration impacts endurance performance in two key ways. One is thermoregulation and the other is cognitive stability. When the water level decreases in the body, the blood plasma volume decreases. This forces the heart to work harder to pump the blood. Therefore, it elevates the heart rate and increases fatigue. At the same time, the reduced cooling capacity leads to a rise in core temperature. The combination is dangerous. The body that overheats and the brain that loses focus. For the athletes whose competitions are longer, dehydration can pull them away from wins.

Even real-life examples prove it. A professional cyclist, Chris Froome, a four-time Tour de France winner, spoke in one of his interviews. Froome has described how hydration strategies have become a turning point in his career. In his early seasons, he underestimated the power of hydration. Due to this, he has to face issues with a physically drained body and mental issues, such as a lack of focus. After working with sports scientists, Froome adopted a hydration plan. He weighed himself before and after stages to track fluid loss. He found improvement in focus and physical stamina, and he has openly credited hydration for that.

The science behind that is straightforward. Proper hydration maintains electrolyte balance in the body. Particularly, sodium and potassium in the body are essential for nerve transmission. Endurance athletes rely on precise neuromuscular coordination—whether it’s the stride rhythm of a runner or the stroke efficiency of a swimmer. When sodium level decreases due to excessive sweating, athletes not only risk muscle cramps but also experience cognitive decline. A 2019 study in the European Journal of Sport Science found that athletes who maintain a good sodium balance finish 9% faster than those who do not. It's because they have sustained mental focus and stamina.

Hydration also interacts with glucose availability in the brain. Dehydration reduces the efficiency of glucose, limiting the brain's fuel supply. That’s why sometimes athletes experience “central fatigue”. It’s the process where the mind gives up before the body does. Neuroscientists explain this as a protective mechanism. When the brain senses stress, it restricts the athlete's ability to perform and prevents form damage. But for an athlete with proper intake of water, this problem does not occur, and prevents them from giving up. Also, it allows them to sustain in the performance both physically and mentally.

The story of swimmers offers another angle to it. A 2021 study conducted on collegiate swimmers at the University of Connecticut demonstrated that even a small amount of dehydration in the body slowed the reaction time during the starting blocks. Even though the difference was measured in fractions of seconds, in competitive swimming, those milliseconds can take you away from medals. The athletes themselves reported being “less mentally sharp” when dehydrated.

For endurance athletes, hydration is not just a one-size-fits-all solution. Individuals' sweat rates vary widely. It can range from 0.5 to 2,5 litres per hour depending on genetics, climate, and intensity. That is the reason why hydration strategies become important at the professional level. Yet for recreational runners and cyclists, the principle holds. Drinking enough water before and after training is not just essential for muscle health but also for mental health, which commands them.

The next time a runner slows down or a cyclist loses concentration, it might not be because of a lack of fitness and training. The reason may be a lack of hydration. Staying hydrated ensures that the body can endure and the mind can remain sharp even in the toughest moments. For an endurance athlete, water isn’t just about thirst. It's about fueling the brain to remain focused and build stamina to achieve the wins.

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References:

• Cheuvront, S.N., & Kenefick, R.W. (2014). Dehydration: physiology, assessment, and performance effects. Journal of Applied Physiology.
• Wittbrodt, M.T., & Millard-Stafford, M.L. (2018). Dehydration impairs cognitive performance and mood. Nutrients.
• Maughan, R.J., et al. (2020). Hydration for athletic performance: The evidence. Sports Medicine.
• Hoffman, J.R., et al. (2019). Sodium balance, endurance, and performance outcomes. European Journal of Sport Science.
• Casa, D.J., et al. (2021). Impact of dehydration on collegiate swimmers’ performance. University of Connecticut study.