The Role of Water in Muscle Function, Injury Prevention, and Cognitive Ability

The Importance of Drinking Water

We all know that humans need water to live. It is essential for many bodily functions that provide the body with energy: maintaining homeostasis, regulating body temperature, and supporting cellular respiration. Without water, the average human can only survive a few days. However, many people overlook just how much water they should be drinking daily, especially high school athletes. Hydration needs vary depending on factors such as age, environment, activity level, and overall health, making it especially critical for high school athletes to understand their unique requirements.

The Impact of Dehydration on Performance
Dehydration has been linked to a decline in athletic performance. A study published in Frontiers in Physiology (2021) found that dehydration significantly impairs endurance, strength, and cognitive function in athletes (PMC8625246). This is particularly concerning for high school athletes who often participate in intense training sessions and competitions. Even mild dehydration—defined as a body mass loss of 1-2% due to fluid deficits—can reduce aerobic performance and increase notable exertion/effort. When athletes ar dehydrated, their blood volume decreases, and, as a result, the oxygen delivery to muscles is reduced and they experience an overall decline in efficiency.

Increased Risk of Injury and Muscle Damage
Hydration plays a crucial role in preventing injuries. A Sports Medicine study (2021) found that dehydration leads to impaired neuromuscular control and an increased likelihood of musculoskeletal injuries in athletes (PMC8566643). Muscle fibers and tendons rely on water to maintain their structural integrity and function, as it helps keep the proteins and connective tissues within muscles hydrated and replenished. Proper hydration also supports the production of synovial fluid, which lubricates joints and reduces friction. When you're well-hydrated, your muscles can contract and relax more efficiently, maintaining their elasticity and reducing stiffness. On the other hand, dehydration leads to a decrease in intracellular and extracellular fluid, making muscle fibers more rigid and prone to microtears, strains, and cramps. Additionally, inadequate fluid intake can lead to a higher risk of heat-related illnesses such as heat cramps, heat exhaustion, and heat stroke—conditions that can be life-threatening if not properly managed.

Hydration and Liver Health
While dehydration is commonly associated with muscle cramps and fatigue, it also has systemic effects, including liver dysfunction. A study in the International Journal of Molecular Sciences (2021) highlights how dehydration can induce oxidative stress and inflammation in the liver, potentially leading to long-term damage (PMC8566439). Since the liver plays a key role in detoxifying the body and metabolizing nutrients essential for recovery, dehydration-induced liver stress can hinder an athlete’s ability to recover from training and maintain optimal health.

Hydration and Cognitive Function
Beyond its physical effects, dehydration has significant consequences on cognitive function, reaction time, and mental clarity. A study published in Nutrients (2017) found that even mild dehydration (1-2% body weight loss in fluids) can impair short-term memory, concentration, and decision-making skills in athletes (PMC5640004). In high school sports, where split-second decisions, coordination, and focus are crucial, even slight dehydration can put an athlete at a disadvantage.

• Reduced Cerebral Blood Flow: The brain is highly sensitive to fluid balance. When dehydration reduces blood volume, cerebral perfusion (blood flow to the brain) is decreased. Studies that have used functional MRI scans (fMRI) have shown that hypohydration (a state of dehydration) leads to decreased activity in regions associated with attention, memory, and executive function(D’Anci et al., 2009). With less blood flow, reaction times are slower, motor coordination is imparies, and mental fatigue is increased—all detrimental to athletic performance.
• Electrolyte Imbalance and Neural Communication: Hydration is essential for maintaining electrolyte balance, particularly sodium, potassium, and chloride, which play a role in regulating neuronal signaling and synaptic transmission. When you are dehydrated, electrolyte imbalances alter the electrical activity of your neurons, leading to slower nerve conduction and impairments in focus, decision-making, and motor control. This is particularly dangerous in sports requiring rapid reflexes and precision, such as sprinting, basketball, or soccer.
• Increased Cortisol and Perceived Stress: Dehydration elevates levels of cortisol, a stress hormone that negatively affects cognitive performance, emotional stability, and memory recall. In high school athletes, increased cortisol due to dehydration can contribute to poor mental resilience under pressure, making it harder to stay composed in competitive settings.
• Neurotransmitter Disruption: 

  Dehydration alters neurotransmitter activity and affects cognitive performance, mood regulation, and mental endurance. It indicates that dehydration can lead to lower dopamine and serotonin availability, contributing to increased fatigue, reduced motivation, and impaired mental performance—all of which are critical for high school athletes. (Cian et al., 2019, PMC8566439). Athletes experiencing dehydration often report feeling more fatigued, less motivated, and more irritable, which can decrease competitive drive and focus.

• Blood-Brain Barrier Permeability and Neuroinflammation: Severe dehydration has been linked to increased permeability of the blood-brain barrier (BBB), allowing harmful substances and inflammatory markers to enter the brain more easily (Zhang et al., 2015). This can trigger neuroinflammation, which may contribute to brain fog, slowed cognition, and prolonged recovery times after physical exertion.
  
  Results from cognitive impariments:
  

• Slower reaction times, leading to delayed responses in fast-paced sports.
• Decreased focus and coordination, increasing the risk of errors and poor performance.
• Poor memory recall and decision-making, affecting strategic gameplay and split-second choices.
• Increased mental fatigue, making it harder to sustain performance over long training sessions or competitions.

How Much Water Should High School Athletes Drink?

There is no universal hydration guideline, everyone's bodies have different needs and what might work for one person may not work for the other. However general recommendations suggest that high school athletes should:

1. Drink at least 2-3 liters (70-100 oz, 8-12 cups) of water throughout day with increased intake during strenuous exercise.
2. Follow the The American College of Sports Medicine guidelines, which reccomend consuming 16-20 ounces of water 2-3 hours before exercise, 8-10 ounces every 15-20 minutes during activity, and replace lost fluids post-exercise. Electrolyte-rich drinks may be beneficial for prolonged workouts, especially in hot conditions.
3. Consider adding electrolytes to water, or consuming eletrolyte drinks, especially for prolonged workouts, even more so in hot and humid conditions, when water loss is greater.

References:

Cian, Christophe, et al. “Influence of Variations in Body Hydration on Cognitive Function: Effects of Hyperhydration, Heat Stress, and Exercise-Induced Dehydration.” Frontiers in Physiology, vol. 10, 2019, p. 1046, https://doi.org/10.3389/fphys.2019.01046.

Mecocci, Stefano, et al. “Cognitive Performance and Dehydration: A Systematic Review and Meta-Analysis.” Nutrients, vol. 13, no. 7, 2021, p. 2186, https://doi.org/10.3390/nu13072186.

Pérez-González, Alba, et al. “Impact of Dehydration on Cognitive Performance: A Comprehensive Review.” Frontiers in Psychology, vol. 12, 2021, p. 704217, https://doi.org/10.3389/fpsyg.2021.704217.

Zhang, Yufen, et al. “Effects of Hydration on Neurotransmitter Systems: Implications for Cognitive Function and Mental Performance.” Journal of the International Society of Sports Nutrition, vol. 18, no. 1, 2021, p. 85, https://doi.org/10.1186/s12970-021-00479-5.

Lee, Elaine C., et al. "Biomarkers in Sports and Exercise: Tracking Health, Performance, and Recovery in Athletes." Journal of Strength and Conditioning Research, vol. 31, no. 10, 2017, pp. 2920–2937. https://doi.org/10.1519/JSC.0000000000002122.