How to Stay Hydrated & Safe During Summer Workouts

When temperatures rise and your training ramps up, hydration becomes more than just a comfort—it's a survival mechanism. Whether you're a marathoner, cyclist, or weekend warrior, understanding how your body regulates body temperature through sweating during exercise is crucial to performance and safety.

And here’s the kicker: emerging science shows that not just dehydration, but overhydration, can be dangerous too—especially for women.

Let’s break it down.

Why Hydration Matters So Much During Exercise

Your body relies on sweating to stay cool. As your core temperature climbs, fluid shifts from your bloodstream to your skin, evaporating as sweat to release heat. When that fluid evaporates, your body is losing fluid. This is a normal process and performance will not be harmed as long as you keep sweat losses under 2% of your body weight lost via fluid. Each person has a unique sweating rate, so there is no one size fits all amount of fluid that athletes should drink, it must be customized.

But lose too much water without replacing it, and you're on the fast track to hypohydration—which leads to low blood volume, reduced sweating, and skyrocketing core temperature. That’s when the risks of heat exhaustion, heat stroke, and performance decline go way up.

Key Mechanism:
Your brain uses sensors called osmoreceptors and baroreceptors to monitor sodium levels and blood pressure. When fluid drops or sodium gets too concentrated, these sensors trigger thirst and release a hormone called vasopressin (AVP), which helps your kidneys hold on to water.

But sometimes, that system gets overwhelmed—especially in endurance events.

Dehydration: The Classic Danger

Even with modern hydration awareness, dehydration remains widespread. In long races, 50–70% of participants still finish losing more than 2% of their bodyweight via fluid in sweat—and about 30% exceed 4% body weight loss (Speedy et al., 1999; Noakes et al., 2005).

Dehydration during exercise:

• Reduces sweat response, limiting heat loss

• Decreases stroke volume and raises heart rate

• Increases cardiovascular strain

• Impairs performance, focus, and endurance

Mild dehydration is expected and tolerable. But once you cross that >2% threshold, you’re asking your body to work harder with less fuel in the tank—literally.

Exercise-Associated Hyponatremia: The Lesser-Known (But Equally Serious) Risk

Hyponatremia occurs when sodium in your blood drops too low—usually from drinking too much hypotonic fluid during long exercise bouts.

This can happen in two ways:

1. Hypervolemic hyponatremia – from drinking more fluid than your kidneys can get rid of, diluting blood sodium.

2. Hypovolemic hyponatremia – from losing lots of sodium in sweat without replacing it.

Symptoms can mimic dehydration: nausea, dizziness, headache, confusion. But it is important to recognize if the symptoms are related to low blood sodium vs. dehydration. 

What’s particularly concerning: some athletes experience no symptoms at first, but when blood sodium drops drastically (below 125 mmol/L), it can cause cerebral edema, brain damage, or even death.

Women and EAH: What the Research Shows

Emerging research highlights that women face greater risk of hyponatremia in endurance events. Why?

• Smaller body size = lower fluid requirements

• Longer finish times = more opportunity to drink excessively

• Estrogen (estradiol) = increased water retention and hormonal changes that may blunt the body’s sodium regulation

Women of reproductive age, in particular, are more susceptible to cerebral complications like brain swelling. This isn’t just a matter of behavior—it’s biology.

How to Train Your Hydration Strategy

Your sweat rate, sodium loss, and fluid needs are unique. That’s why a one-size-fits-all approach doesn’t work.

Here’s a better playbook:

1. Measure your sweat rate: Weigh yourself before and after training. Losing 1 kg (2.2 lbs) = ~1 liter of sweat loss.

2. Track your fluid intake: Know how much you drink during sessions.

3. Include sodium strategically: Add electrolytes to your fluids, especially in long or hot workouts.

4. Match practice to race conditions: Test your hydration plan in training—don’t wait until race day.

5. Be alert to symptoms: If you're nauseated or light-headed, consider both dehydration and hyponatremia. Having a customized hydration plan can help reduce the risk of both.

Field vs. Lab Research: What It Means for You

Field studies tell us how athletes respond in real-world conditions—but are limited in control. Lab studies can explore precise mechanisms—like how sodium affects fluid retention or how hormones impact water balance.

Together, they give us a fuller picture. And here’s the takeaway: hydration science is evolving, and staying informed can give you a real edge.

How Sports Drinks Can Help

Sports drinks aren’t just about taste—they’re designed to help maintain hydration and electrolyte balance. One liter of a sports drink with 20 mEq/L of sodium delivers about 460 mg of sodium, helping:

• Preserve blood volume

• Maintain thirst cues

• Stimulate fluid retention

• Reduce EAH risk (if not over-consumed)

For athletes who sweat heavily, especially in long or hot events, choosing a drink with sodium—or supplementing with electrolyte tabs or gels—can be game-changing.