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Why does heat make you feel sleepy?

Written by Tuck Staff

Why is it that you can feel exhausted after a day at the beach, but painfully awake when you open your curtains to bright sunshine in the morning? What can explain this apparent contradiction?

While the sun’s light wakes you up, its heat makes you sleepy, Once you know that, it all starts to make sense.

But why exactly does heat make you so tired? From dehydration to skin damage, heat creates physical effects in your body that combine to make you sleepy.

Reasons why heat makes you tired

Heat changes your body temperature.

You may not realize it, but your body is constantly working to keep you in balance. It regulates your moods, your emotions, and your body temperature. External factors, such as the temperature of your environment, as well as internal factors, such as your heart rate and metabolic rate, all impact your body temperature. Your body responds to these changes to maintain your ideal body temperature, expending energy in the process and making you feel tired.

Even if you’re just sitting there tanning, when the sun’s heat is shining down on you, it naturally heats you up. When that outdoors time is coupled with physical activity, the changes are even more pronounced. And the effects are even more extreme for those who are overweight – the bigger the body, the more your body has to work to get everything where it needs to go.

Heat makes you dehydrated.

The reason we easily become dehydrated in the sun is two-fold: our body is working harder to maintain our base temperature (see above), and we may be losing additional fluids if we’re sweating as well. Plus, we often forget to up our liquid intake when we spend long amounts of time outdoors.

Remember to drink before you get thirsty. When you start feeling thirsty, that means you’ve already lost some of your body fluid. As a result, your body loses blood volume, so your heart has to pump even harder to get blood, oxygen, and other nutrients to your brain.

Heat causes other chemical changes to your body.

As you know, the sun does more than just make you feel hot. Its powerful ultraviolet rays cause chemical changes to your body, including sunburn, pigmentation changes, and wrinkles. The more time you spend in the sun, the sooner your body starts working to fix the damage done, resulting in fatigue.

This is especially true in the case of sunburn. With sunburns, your body moves fluid toward the skin that’s been burned to address that issue, meaning that there’s less fluid elsewhere to sweat, reducing your ability to cool yourself and increasing your risk of dehydration and fatigue.

Depending on how much time you spend outside and your physical activity, you may be at risk of heat exhaustion or heat stroke. If along with sleepiness, you start to experience extremely heavy sweating, dizziness, flushed skin, nausea, lightheadedness, headache, or a weak or rapid pulse, immediately seek medical attention and get to a cooler area.

Heat tricks your brain.

Sometimes the fatigue doesn’t set in until after you’ve removed yourself from the sun. If you spent a large amount of time outside, the transition back indoors can cause an exhaustive effect.

Depending on how dark your indoor environment is, the contrast from sunlight to indoor lighting can trick your brain into thinking it’s time for sleep, kickstarting your melatonin production.

Tips for avoiding heat fatigue

Follow the below tips to avoid heat fatigue. Not only will they prevent you from getting tired, they’ll also help you avoid some of the other consequences of spending too much time in the sun.

1. Stay in the shade when you can.

The best way to avoid heat fatigue, as well as sunburn, dehydration, and skin damage, is to stay out of the sun. You’ll still get plenty of benefits simply from being outdoors, but you won’t get as hot.

Seek out shade whenever possible, limit your time outdoors during the hottest parts of the day, and wear hats or long-sleeve (but breathable) shirts.

2. Stay hydrated.

The best way to avoid dehydration is by staying hydrated. Makes sense, right?

Bring along a refillable water bottle, and know where your closest drinking fountains are. Eat foods that have a high water content, such as fruits and vegetables.

Remember that all liquid is not equal when it comes to hydration. For example, liquids such as alcohol are diuretic and will only increase your dehydration.

3. Eat salty snacks.

When you sweat, you not only lose water, but also salt and other electrolytes, so staying salty keeps you better hydrated as well.

Bring along some healthy salty snacks, such as pretzels or nuts, to keep you feeling well when you’re outdoors.

4. Take breaks.

When you’re engaged in physical activity outside, it’s important not to overextend yourself. Your body is already working harder than normal to maintain your body temperature.

Whether you’re exercising or working, take more breaks than you would if you were indoors, and consider taking it a bit easier on yourself as well.