High and dry: six myths about hiking in the heat

Posted by Carey Davies on 02/07/2015
Ron Burgundy: wrong about milk

Heat and sun are unusual hazards in our mountain areas, but it’s worth debunking some of the myths around exercise in hot conditions.

Hot weather in Britain is, let’s face it, freakish. On the odd occasion when it does arrive, it's brilliant. There’s great joy to be had in strolling around in the Moelwyns pretending you’re actually somewhere like Majorca.

But high temperatures and burning sun also come with dangers. Heat exhaustion and the much more serious heat stroke can strike with surprising ease and rapidness – particularly if, like most Britons, you’re not really used to it.  

Perhaps because of our lack of familiarity with that big yellow ball in the sky, people’s grasp of the dangers posed by hot weather is not always perfect. We debunk some of the more popular myths and give you some tips to embrace the heat and sun safely.

Myth number 1: The British sun can’t harm me

As the song goes, ‘Mad dogs and Englishmen go out in the midday sun.’ We are notoriously bad at coping with sunshine. Nowhere is this more evident than at home, as a glance at the red-faced crowds outside any given Lake District pub at the end of a sunny day will confirm. From time to time we’ve all forgotten that the sun is still a gigantic ball of UV-emitting nuclear fire, even in Langdale.    

Some basic tips: a water-resistant or waterproof suncream is best as they won’t dribble off after five minutes of sweating uphill, but even these need to be reapplied eventually after enough perspiration. A hat with a wide brim will protect your face and shoulders and provide shade. For other clothing, think loose, light garments like zip-off summer trousers and long-sleeve button shirts.

And in the long days of summer, early starts and late finishes with a shady rest during the heat of the day can be a simple way to enjoy the hills in peace and comfort. You also get to see more wildlife early and late because animals are far more sensible than we are.

Myth number 2: You need to drink even when you’re not thirsty

For a long time, common wisdom among sports and fitness types held that if you become thirsty it was ‘too late’ – you were already suffering the effects of dehydration. Consequently it was best to drink continually during exercise. But in recent years the view seems to have shifted, with some physiologists arguing that distrusting your thirst in this way could even lead to drinking too much.

In truth, hydration needs will vary from person to person, and the best advice now seems to be – drumroll – drink when you’re thirsty.

No surprises there, then. But it’s easy to underestimate the amount of water you need in hot, windless weather. It’s prudent to take more water than you think you might need. As a guide, for the average person three litres or more is often not excessive for a big day in the hills when the mercury soars.

Myth number 3: Water is all you need to stay hydrated

In the movie ‘Anchorman’, Will Ferrell’s wayward newsreader Ron Burgundy famously lamented his choice of hot-weather beverage with the words: “milk was a bad choice.” It turns out he was wrong; semi-skimmed or low fat milk is actually a good rehydration drink in hot weather.

Okay, milk may not be the most practical choice for when you’re actually out on the hill – a carton of curdled dairy product is no one’s idea of a refreshing beverage – but the reason why it’s a good choice are instructive. It has to do with its salt and mineral content. Sweating through exercise causes you to lose both water and things called electrolytes, which in layman’s terms basically means salt. The term ‘dehydration’ is actually generally used to refer to both loss of water and electrolytes, both of which the body needs. It also needs them in the correct balance. Ever wondered why you get thirsty from eating salty foods? It’s because this balance has tipped too far in the direction of the electrolytes, and the body has to compensate.

Conversely, too much water without electrolytes is bad for the body too. For most hill activities electrolytes can often be kept up through food; a packet of peanuts nibbled on through the day in addition to your usual food, for example, will usually suffice. Sports drinks and other products containing electrolytes of the sort used by runners and athletes are typically overkill, but in really hot weather it might be worth keeping one or two in reserve in case you become very dehydrated or start to feel the onset of heat exhaustion. Which brings us to our next myth…

Myth number 4: Heat exhaustion and heat stroke are the same thing

Another common misconception is to mix up heat exhaustion and heat stroke. Both are indeed heat-related illness, but one is considerably more serious than the other.

Heat exhaustion is caused by water and electrolyte loss. It’s not a life-threatening condition in itself, but it can be a precursor to heat stroke, which is far more serious, if action isn’t taken. A few hours of strenuous exertion in the sun are enough to acquire the early symptoms of heat exhaustion, which include heavier-than-usual sweating, rapid breathing, nausea, a fast, weak pulse, light-headedness, and a feeling of heavy, stultifying tiredness. Heat cramps – sharp pains in the abdomen arms and calves – can also result. If you start to feel these, slow it down: top up your water and electrolytes, seek some shade, have a break, and adjust your pace.

If you don’t do the above, you could be at risk of heat stroke. Heat stroke is a serious, life-threatening emergency triggered by the body generating heat faster than it can shed it, causing core temperature to rise to dangerous levels. This in turn causes the brain to fail. Heat stroke can kill in as little as 30 minutes, so it’s vital you can recognise the symptoms and take action before it’s too late.

Signs of heat stroke include a very high body temperature (about 40C or above), a rapid, strong pulse, rapid breathing and muscle cramps. Very heavy sweating that suddenly stops is also a major warning sign.

Myth number 5: If I have heat stroke I’ll be able to recognise it

A person with heatstroke may also be confused, irritable, restless or hallucinating, so by the time it strikes it will probably be up to others to take action. If you’re with a group, look out for each other and keep an eye out for signs that someone might be succumbing – very irrational or irate behaviour is an easy-to-spot giveaway.

The first thing to do if you suspect someone of having heatstroke is to call for medical help – Mountain Rescue, if it’s available. In the meantime, move the victim somewhere cool, give them fluids to drink – preferably just water – and if possible cool their skin by placing wet clothing on it.

Myth number 6: Swimming – it’s best to plunge right in instead of taking it slowly

Very few things in life are finer than a swim in a cool mountain tarn or river at the end of a sweltering day in the hills. But while it might be awfully tempting to leap straight in to that shimmering, sun-kissed water, such a drastic change in temperature can cause the body to momentarily shut down.

A safer bet is to ease yourself in gradually – even if it’s more painful – and avoid straying too far out into deep, cold bodies of water like lakes and reservoirs. Stay close to the shoreline, and don’t go out alone.

WARNING: Are you a fell runner or endurance athlete? Read this warning over non-steroidal anti-inflammatory drugs (NSAIDs):

 This article has been checked and approved by Dr David Hillebrandt, honorary medical advisor to the BMC. In addition to the advice above, he has asked us to include the following warning to endurance athletes (hill runners etc) who take NSAID drugs such as ibuprofen for pain relief during their exercise:

 “There is no doubt that a combination of taking NSAIDs such as ibuprofen and heavy prolonged exertion combined with dehydration can lead to acute kidney failure. Mountain endurance athletes should not take NSAIDS routinely.”


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1) Anonymous User
19/07/2013
I recommend changing the statement 'The term ‘dehydration’ is actually generally used to refer to both loss of water and electrolytes' to include 'in this context' if you want accuracy.

The only time I've seen it used to describe more than the losing of water, is in exercise magazines etc, and not in scientific papers (which I read far more of). This is for clarity's sake, of course.

Other than that slight niggle, great article.
2) Anonymous User
19/07/2013
Very useful in the current weather, thanks a lot.

I find that adding anything to water tends to just make my water bottles go horrible, especially difficult to clean parts like those in a camelback.

I suggest simply using water in your bottles, but making sure that you can get the salts that you've lost to sweat through the food you are snacking on.
3) Anonymous
21/07/2013
This comment broke the house rules and has been removed
4) Anonymous User
22/07/2013
Great article, thanks for the advice!

I used to always have a pint of milk after lacrosse training at uni & when I finished the TMB last year the same applied. My friend said that milk wasn't good for you in such circumstances but its always worked well for me. So thanks for the vindication & the reassurance that I'm looking after myself properly.
23/07/2013
Excellent advice!
It is also worth remembering that you can get sunburnt even on cloudy days during the summer.
6) Anonymous User
31/07/2013
Great Advice due to the fact I am going walking in the lake district soon! Thanks
7) Anonymous User
17/07/2014
Heat stroke: I'm normally confused, irritable and restless - I'll keep an eye out for the hallucinations.
8) Anonymous User
17/07/2014
I smile when I see people carrying water during 5k parkruns. I only ever took water on board in races longer than 10 miles. I even did so with temperatures in the 80s with no ill effect. The only time I suffered in a race was in a half marathon on a blisteringly hot evening when because of an organizational error the only fluid was at the 10 mile point. When in the mountains I did manage to use up 3 litres of fluid when climbing Ben Nevis via the CMD arete. Again that was on an unusually hot day. I filled a litre water bottle at the Red Burn on the way down and I had drunk that before I reached the car park. I now make sure I have water to spare when I know I am away from reliable sources and I always wear a hat.

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