If heading off somewhere sunny on holiday always leaves you in need of an afternoon nap, or you feel more tired than usual whenever a rare British heatwave rolls around, you're not alone – and there are a few good reasons why you might find yourself snoozing more (or even feeling just plain exhausted) in hot weather.
Dr Aimée Brame, a Consultant Physician at London Bridge Hospital (which is part of HCA Healthcare) says it's not uncommon to feel sleepier than normal when the weather is hot. She adds that there are essentially three reasons for it too, with the first being that your body is working in overdrive to regulate your temperature.
"It takes a lot of energy to maintain the temperature of the body, keeping cool takes effort," explains Dr Brame. "Maintaining a constant internal temperature is vital for normal body function. The brain detects a rise in blood temperature and causes the body to sweat and blood vessels to dilate to lose heat – these processes are active and require energy."
She continues on to say that high outside temperatures and an increase in sweating can also result in a degree of dehydration, which in turn can leave you feeling lethargic. "In addition to fluid loss, the loss of essential salts and electrolytes such as potassium, calcium and magnesium can also make you feel worn out," Dr Brame adds, giving a welcome reminder of the importance of staying hydrated on sunny days.
Another couple of common reasons for drowsiness when the temperatures soar? If you've done a workout in the high heat, that could well be a contributing factor. "Extreme exercise should be avoided in the heat, and you may need to alter your training routine and start much earlier or later in the day to avoid the heat," says Dr Brame. "Or, consider switching to cooler activities such as swimming."
Finally, many people struggle to fall or stay asleep in hotter temperatures, and we all know poor slumber makes you more tired the following day.
How can you feel more energetic in the heat?
Dr Brame has several helpful suggestions when it comes to clawing back some much needed energy and alertness:
Stay in the shade to reduce overheating - it will also help to protect the skin from sun damage.
Try to wear loose clothing in natural and breathable fabrics. A wide brimmed hat helps to minimise sun exposure too.
Avoid the sun if you can between 11am and 3pm, when it's at its peak.
Taking cool showers or baths can help reduce body temperature quickly.
Ensure that you do not get dehydrated – drink plenty of fluids and keep a glass of water by your bed.
Alcohol is a diuretic and will worsen any dehydration, so it's best to consume any in moderation and ensure plenty of non-alcoholic fluids are also taken on board.
Caffeine is also dehydrating, so is also best avoided.
Snack on fruit and vegetables as they are full of minerals and electrolytes. Berries, bananas, melon, and even frozen grapes are a great source of vitamins and fluid.
Occasionally a small salty snack may be necessary, particularly if exercising for over 2 hours in hot weather - but you must drink plenty of water to go with it!
Is it bad to nap during the day?
Well, that all depends on the reason why you're tired in the first place. "For some of us, it is just the hangover from a long period of hard work before a holiday, or the sensation of relaxation brought about by warmth," says Dr Brame. "The body is a creature of habit, and it is better to try to stick to usual routines and try to avoid the overheating in the first place."
Interestingly, she adds, we keep cooler at night when wearing PJs as sweat is wicked away from the skin by clothing – so going naked isn't actually the best solution. Opting for natural fabrics and taking a cool shower before bed will work wonders instead.
Also - keep in mind that if you're feeling lethargic to the point of not being able to work, or socialise, it could indicate a more serious problem. "Extreme tiredness can be more concerning," says Dr Brame. "Heat exhaustion and (the more serious) heat stroke are potentially very dangerous."
What is heat exhaustion?
The signs of heat exhaustion include: having a headache, dizziness, nausea, excessive sweating and clammy skin. "The person may complain of cramps in the hands and feet too, and of feeling very thirsty," explains Dr Brame. "They will have a high temperature, and children can become floppy and sleepy."
Heat exhaustion needs to be treated quickly by moving the person to a cool place and getting them to lie quietly and drink plenty of water. "External cooling by sponging or spraying with tepid water can help reduce the temperature and they should feel better in around 30 minutes," she adds.
If after half an hour of rest in a cool place you notice the person is not sweating, or that their temperature has continued to rise, or they become confused or lose consciousness, this is an emergency. "The person may even have seizures, so in this instance it's important to call an ambulance immediately," says Dr Brame. However, this is of course at the more extreme end of the scale.
So, there you have it: if you're feeling sluggish in the heat, it could be down to dehydration, your body working extra hard to keep you cool, or generally just being more relaxed in the sun – or a combination of all three. Either way, we're pretty sure it's a good excuse to eat an ice lolly in the shade?
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