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Hydration breaks have become a storyline during this summer's FIFA World Cup as officials pause play in each half so players can cool down and rehydrate.

While most people won't be competing on soccer's biggest stage, millions will spend time running, hiking, cycling, and exercising outdoors during the hottest months of the year. We spoke with , assistant professor of at UNH, about what we can learn from the World Cup hydration breaks, how heat affects the body, and what everyone should know before heading outside this summer.

What benefits do scheduled hydration breaks provide for athletic health and performance?  

There's certainly a benefit to giving athletes an opportunity to hydrate during a scheduled break. They're likely drinking a combination of water and electrolyte beverages rather than just water. It's also helpful to give fans time to get some water.  

What you're really doing is giving athletes time to drink without feeling rushed because someone is injured or play has briefly stopped. You're also giving their bodies time to start cooling down, which is one of the biggest challenges during hot, humid summer conditions.

From a competitive standpoint, these breaks help athletes maintain peak performance. Once dehydration causes an athlete to lose more than about 2% of their body weight, physical performance begins to decline. Scheduled hydration breaks give athletes the opportunity to replace fluids before dehydration starts affecting how they play.

How does dehydration affect athletic performance?

Typically, athletes notice they start feeling sluggish. They don't feel as explosive and they fatigue more quickly during play. This is because the body's cardiovascular system is working hard to shift blood to your skin to help cool the body, and send blood to your skeletal muscles. When you don't have as much blood going to your muscles, this will shift how your body is using different fuel sources.

Inside the muscles, we store glycogen, which is essentially stored sugar. Hotter conditions will cause you to use more muscle glycogen. As those glycogen stores become depleted, fatigue sets in faster. Athletes may also begin experiencing cramps when dehydrated, which is not helpful during competition.

In addition to staying hydrated during games, athletes should prepare before they even step onto the field. During the summer, they shouldn't train only in air-conditioned environments. Exposing themselves to warmer conditions over about 10 days allows the body to acclimate and better handle exercising in the heat.

Most of us aren't playing in the World Cup, but many people will be running, hiking, biking, or playing recreational sports this summer. What should people know about staying properly hydrated while exercising in the heat?

Michael Brian

Once we lose more than about 2% of our body weight through water loss, that's where we begin seeing declines in exercise performance.

One simple thing people can do is establish a baseline body weight over several days and then weigh themselves after a hike, a workout, or competition. Water is usually the first thing your body loses during exercise, so that difference gives you an idea of how much water you need to restore your hydration.

It's not simply about drinking water. It's also about replacing electrolytes like sodium and chloride.

For healthy individuals, adding a little more salt to your diet during the summer can help the body retain water. Of course, people with hypertension, heart disease, or kidney disease need to be more cautious and should follow medical advice.

Is water enough, or are there times when sports drinks are a better choice?

I think a combination of water and electrolyte beverages is best, particularly during longer events. Sweat contains electrolytes, so replacing both water and electrolytes helps improve water retention while restoring what you've lost during exercise.

That's why sports drinks or electrolyte tablets can be useful during longer workouts or competitions.

How can people tell they’re becoming dehydrated?

Thirst is one of the earliest signs of dehydration.  Specialized receptors in the brain detect changes in sodium concentration in your blood. As you lose water, sodium becomes more concentrated, which triggers your thirst response.

Urine color and urine frequency is another simple indicator. If your urine is dark yellow — or you're not using the bathroom as frequently — that could be a sign you are dehydrated and need to drink water.

Dehydration is sometimes hard to spot as some people might not be able to sense that thirst trigger as a sign of dehydration, particularly older adults — so if you begin to feel confused, dizzy, unusually fatigued for the same activity, or nauseous, your priority should be to get out of the heat and cool your body. Move into the shade, get into air conditioning, or use fans to help lower your core temperature. If your symptoms don't improve, you should seek medical help.  

What are the biggest hydration mistakes recreational athletes make?

The biggest mistake is simply not drinking enough.

Depending on the conditions, people can lose anywhere from about half a liter to two liters of sweat every hour during exercise or competition in the heat.

A lot of people don't realize that replacing electrolytes is just as important as replacing water. Drinking excessive amounts of water without replacing electrolytes can dilute the sodium in your blood and potentially lead to hyponatremia — so the combination of both helps your body retain fluids longer and minimizes the effects of heat and dehydration.

What’s the most important hydration advice you’d give people this summer?

Drink throughout the day instead of trying to drink a large amount all at once. Your body will simply eliminate much of that excess water, which might not rehydrate you fully.

It's also important to plan physical activity for the cooler parts of the day, such as early morning or the evening, and avoid strenuous exercise during the hottest part of the afternoon whenever possible. Your workouts won't be as effective.

Finally, don't be afraid to spend time outdoors. Your body actually adapts to warmer temperatures over time. Build this up slowly with short, repeated exposures that will help to regulate your body better during these hot summer months.  

Just make sure you're bringing water with you, wearing lighter clothing, and pay attention to how you feel. Lastly, I always recommend checking in on older adults and young children, who are at greater risk for heat-related illnesses.