Fancy a hike in the sunshine? A few sensible precautions to prevent heat exhaustion and heatstroke will go a long way
With British summers so unreliable, it’s no wonder many of us are keen to make the most of the sunshine when it shows up, and a leisurely walk – or a strenuous hike – is a great way of getting outdoors into the fresh air.
But slapping on the SPF to protect your skin isn’t the only health concern to be aware of; it’s important to consider the risk of heat exhaustion and heatstroke too.
These conditions are directly linked with body temperature, so they can occur in any scenario where there’s sufficient heat – sitting in hot, stuffy cars is notoriously dangerous – but they should be a prime concern for anybody thinking about undertaking exercise, even if that’s just a gentle hike, on a hot day.
So what exactly are heat exhaustion and heatstroke?
Many of us will have experienced heat exhaustion at some point; chances are you felt unwell, utterly drained of energy, agitated and even a bit panicky.
It occurs when a loss of body fluids and salts, due to exposure to heat, causes a sufficient decrease in blood pressure and blood volume.
“Someone with heat exhaustion may feel hot, sick, faint and sweaty,” says Dr Annabel Bentley, medical director at Bupa UK. “Help move them to a cool area, loosen tight clothing and give them some water. They should start to feel better within half an hour or so.”
Heatstroke, on the other hand, is a medical emergency, and it’s vital that somebody with suspected heatstroke is given urgent treatment or organ damage, and even death, may occur.
It happens when a person’s temperature is so high that their body’s cooling system stops working, which basically means they can no longer sweat – this is a key indicator for heatstroke.
So look out for dry skin with no sweat; a person may also display signs of mental confusion, vertigo, rapid shallow breathing (hyperventilation), muscle cramps, nausea and vomiting, loss of consciousness and even fits.
Spot these symptoms and you should dial 999 immediately. In the meantime, moving them to a cool, ventilated area, giving them some water to drink if they’re conscious (but don’t give any drugs or painkillers), and showering their skin in cool – but not freezing cold – water, or applying damp, cool towels, can help.
So while heat exhaustion is far more common and not as serious, it still needs to be addressed with attempts to cool down, or it could eventually develop into heatstroke.
Also, certain people may be more at risk of adverse reactions to heat.
“People who are more at risk include babies and young children, the elderly and those with existing medical conditions like heart problems or diabetes,” adds Bentley.
If you are thinking of heading off for a long walk or hike in the sunshine, preparing for the heat is vital – starting with hydration.
“Our bodies work a bit like a combustion engine and if they overheat, they can’t function,” says Nuffield Health physiologist Jessica Bonstein. “Sweating is the natural means by which the body cools itself. It’s important that when exercising in the heat, people stay well hydrated to facilitate the safe loss of bodily water through sweating.”
There’s no official guideline about how much additional water you may need for each extra degree on the thermometer, but little and often is a good place to start.
“The rate at which heat begins to have an adverse affect can happen very quickly,” notes Dr Emma Derbyshire, a leading nutritionist and advisor to the Natural Hydration Council. “People can lose about two to four litres of fluid within an hour. Some of that depends on other factors like age, temperature, body size and sex, but you can lose up to four litres an hour which is quite a lot, so it’s definitely important to make sure you take in enough fluid, and what’s best is to make sure you have small amounts and often, about 250ml every 20-30 minutes is a good guide.
“If you’re doing a race or hike and don’t drink for 45 minutes or an hour, and then guzzle down lots of fluid later on; you really want to avoid doing that. Pacing your intake is better for helping you avoid dehydration and heat exhaustion.”
It’s advisable to have water as your first-choice drink, and water alone is usually sufficient if your activity lasts for an hour or less. If you’re on a longer walk or hike, you may want to top up energy reserves with a sugary or fruity drink or isotonic sports drink to replace lost electrolytes.
Rehydrating after you’ve finished your activity is useful too. A good way to find out just how much water you’ve lost is to weigh yourself before and after, which shows how much fluid you’ve lost – then drink that amount; 1kg of weight equals 1L of fluid.
Also important is ensuring you wear appropriate clothing and a wide-brimmed sunhat (sunglasses alone won’t cut it), and be sensible – if you’re not in the best physical shape and know you don’t respond well to heat, heading out for a strenuous eight-hour walk on the hottest day of the year probably isn’t a good idea.
But remember, too, even the fittest of folk aren’t immune to the effects of heat.
“A person’s ability to cool themselves efficiently is relative to the climate they’re used to exercising in, so someone can be fit in a relatively temperate climate but suffer heatstroke when exercising in high temperatures,” says Bonstein.
Whether it’s a humid or dry climate will make a difference too. “The sweat rate in humid heat is greater than in dry heat, however dissipation of sweat, thus cooling, is more efficient in dry heat,” Bonstein adds.
If you’re going to be exercising in particularly challenging climates, acclimatise by building up resistance slowly – Bonstein advises a period of at least two weeks.
Cramps are a signal you’re very dehydrated, so don’t ignore them. “It’s fair to assume that most people experiencing cramp will stop exercising. However, some may stretch it out and carry on – bad idea!” notes Bonstein.
“Fainting due to the heat is common but has less to do with water loss and more to do with vasodilation and blood pooling, as the blood vessels near the skin dilate to allow for greater blood flow to the skin to cool off,” she adds. “Should you feel at all faint or light-headed, it’s advised to stop exercising and find some shade. If symptoms persist, call an ambulance as you may already be dehydrated and heatstroke may follow quickly.”
