--- title: "You’re Probably Under-Hydrated: Why Your Muscles, Brain, and Heart Care About Water & Electrolytes" entity: "blog" canonical_url: "https://www.andreaproulxnd.com/blog/you-re-probably-under-hydrated-why-your-muscles-brain-and-heart-care-about-water-electrolytes" markdown_url: "https://www.andreaproulxnd.com/llms/blog/you-re-probably-under-hydrated-why-your-muscles-brain-and-heart-care-about-water-electrolytes" lastmod: "2026-05-01T01:37:00.000Z" --- Here's part 1 of a two-part guide for active athletes who want their hydration strategy to work as hard as their training. Athletes track training load, macros, and recovery metrics. Yet one of the most powerful performance variables is often handled all too casually: hydration. Fluid balance directly influences muscle contraction, neurological function, cardiovascular stability, and cognitive decision-making during sport. This poor decision making is often noticed by teammates: “why did she make that pass?”, “why didn’t’ she make that throw?”, “that’s odd, what a weird decision”. Even small deficits matter. Research consistently shows that just 2% dehydration can reduce speed, reaction time, and mental focus . For athletes in cycling, running, and team sports, that drop can show up as slower sprints, poorer decision-making, or earlier fatigue. Hydration isn’t simply “drink more water.” It’s a physiological system involving fluid volume, sodium balance, and electrolyte transport across muscle and nerve cells. This two-part guide breaks down how to hydrate strategically. ### Part 1: Hydration Fundamentals for Athletic Performance #### Why Hydration Directly Impacts Performance Water supports nearly every system – and every cell - involved in training and competition. Key physiological roles: li]:pl-0 [&>li]:marker:text-current [&>li]:marker:text-[1.2em] [&>li]:marker:font-normal">- Maintains blood volume and oxygen delivery - Supports thermoregulation during exercise - Enables nerve signaling and muscle contraction - Helps maintain cognitive focus and reaction speed - Supports recovery and metabolic waste removal Even modest dehydration can increase cardiovascular strain and perceived exertion. Making every workout feel harder, and every training session require more from your brain and motivation. For athletes balancing training, work, and [mental load](/blog/mental-load-and-recovery-the-hidden-factor-impacting-your-performance-why-balancing-life-work-and-sport-requires-more-re), hydration also influences neurological recovery and cognitive clarity. Daily Hydration Targets for Active Adults Baseline fluid needs vary depending on body size, environment, and training load. General daily targets: li]:pl-0 [&>li]:marker:text-current [&>li]:marker:text-[1.2em] [&>li]:marker:font-normal">- 1.5–3 L fluid per day depending on activity and climate - 6 mL/kg body weight every 2–3 hours Example: li]:pl-0 [&>li]:marker:text-current [&>li]:marker:text-[1.2em] [&>li]:marker:font-normal">- 60 kg athlete → ~300 mL every 2–3 hours Urine colour remains one of the simplest markers. Goal: pale yellow urine throughout the day. Everyday hydration isn’t just about what you drink, but also how well your gut absorbs fluids – everyday and in training. Endurance training and heat stress can strain the intestinal barrier and contribute to GI distress in athletes. For a deeper look at this physiology, read [“ Leaky Gut: Why Your Gut Barrier Matters More Than You Think.”](/blog/leaky-gut-why-your-gut-barrier-matters-more-than-you-think) ### Pre-Exercise Hydration Strategy Starting exercise slightly dehydrated compounds fatigue later in the session. A simple pre-exercise protocol: • 500 mL water 1–2 hours before training or competition However, individual tolerance matters. Some athletes feel heavy or bloated if they drink too much immediately before exercise. Tracking your own response is key. Pro Tip (and heads up) – low grade food intolerances can cause bladder irritation leading to and increased desire to pee. Reducing the clarity that tracking urination as a hydration marker can offer. Super pro tip: gluten is a known bladder irritant. ### Hydration During Training and Competition During longer or higher-intensity sessions, fluid loss increases quickly through sweat. Recommended intake during sport: • 150–350 mL every 15–20 minutes during exercise lasting longer than 60 minutes For sessions exceeding 90–120 minutes: • ~500 mL fluid per hour is often required This helps maintain plasma volume and sustain cardiovascular output. ### Signs and Symptoms of Dehydration Athletes often overlook early dehydration signals. Common indicators include: li]:pl-0 [&>li]:marker:text-current [&>li]:marker:text-[1.2em] [&>li]:marker:font-normal">- Crystallized salt residue on skin after sweating - Dark urine or high urine specific gravity - Muscle cramps or spasms - Headaches or morning headaches - Dry mouth or excessive thirst - Fatigue or unusual weakness - Nausea - Heart palpitations These symptoms often appear before performance noticeably declines. Hydration isn’t just about fluid volume. Hormones such as cortisol also influence sodium and potassium balance in the body, which affects muscle contraction and fatigue. If you want to understand how stress physiology changes recovery and muscle performance, read “[Is Stress Holding Back Your Strength? The Surprising Link Between Cortisol and Muscle Recovery.”](/blog/is-stress-holding-back-your-strength-the-surprising-link-between-cortisol-and-muscle-recovery) ### When Electrolytes Become Necessary Plain water works well for many training sessions. However, electrolytes become important when sweat losses rise. Situations where electrolyte intake improves hydration: li]:pl-0 [&>li]:marker:text-current [&>li]:marker:text-[1.2em] [&>li]:marker:font-normal">- Hot weather above 25°C - Humidity above 60% - High sweat rates during intense exercise - Endurance activity longer than 60 minutes - Athletes prone to dehydration headaches Electrolytes help maintain fluid balance inside and outside cells, particularly within muscle tissue. That’s where sodium and potassium enter the picture. Here' s a handy[Hydration Guide for Active Women - get it here.](https://andreaproulxnd.com/hydrationguide/hydrationguide) [In Part 2](https://andreaproulxnd.com/blog/heat-acclimatization-for-athletes-part-2-game-day)we'll talk about Electrolytes, Sodium, and Carbohydrates in Sports Hydration