The subtle signs of heat stroke – and how to exercise safely in a heatwave

In the current hot weather, your main goal may be moving as little as possible. But the high temperatures are set to last for some time yet, and many people are working out how it will impact their exercise routine.

Getting overheated can be dangerous, and exercising when temperatures are high is the prime risk factor for heat exhaustion and potentially deadly heat stroke.

But you don’t have to give up on exercise in a heatwave, says Dr Ross Hemingway, a sports GP and advisor to the Ministry of Defence Commando Training Centre Royal Marines. “Exercise is important, and we don’t need to cancel plans – we just need to put in some simple adjustments.”

Here’s how to recognise the first signs of heat stroke, and make sure you stay safe.

Body is constantly generating heat

Heat stroke, also known as severe heat illness, is when body temperature rises over 40°C. Normal body temperature is about 37.5°C. If it rises to between 38.5 and 40°C, this is called heat exhaustion, or mild heat illness.

Even at rest, the body is constantly generating heat, as a byproduct of the metabolism, when energy is released from food. Normally we can get rid of the heat by sweating, and sending more blood to the surface of the skin if necessary.

When we exercise, though, muscles release much more heat than usual – and this is why heat illness usually develops in people undergoing physical activity.

Spotting signs of heat stroke

Symptoms of heat exhaustion include feeling excessively hot or tired, as well as nausea, vomiting, a headache, dizziness or tunnel vision.

If this progresses into heat stroke, the person starts to become confused, irritable, and behave oddly, and may even turn aggressive with those trying to help them. It can lead to liver, kidney and brain damage – which could be deadly.

Susceptibility to heat exhaustion is variable: two people could do the same level of exercise under the same conditions, and only one would succumb. It seems that some people are just more efficient at getting rid of heat, especially if they are fit, or better acclimatised to warmer temperatures.

Because of this varying susceptibility, organisers of endurance events like long-distance runs should be aware that heat illness can strike some people at any time of the year, even when temperatures are cool, say the UK’s national guidelines on Pre-hospital Management of Exertional Heat Illness.

Other subtle, potential causes

A person who was subtly ill before the activity may also have a greater chance of getting heat stroke. People should be very cautious about exercising in hot weather if they have even a minor illness, like a cold or diarrhoea, says Dr Hemingway.

“If you have a runny nose and have a fever with that, then we know that if you do hard intense exercise, then you’re four times more likely to get heat stroke.”

Vulnerability can also be influenced by whether you’ve been drinking the night before. Alcohol directly impairs the body’s ability to regulate temperature. It also makes people dehydrated the next day, which reduces sweating.

So people should also avoid intense exercise if they feel hungover, Hemingway adds.

Drink enough but not too much

Making sure we are not dehydrated is a key defence against heat stroke. But drinking too much fluids is also a danger, as it can lead to sodium concentration in the blood falling too low.

People are generally advised now to “drink to thirst” – in other words, making sure that they drink enough that they don’t feel at all thirsty – but no more.

People doing exercise should aim to drink to thirst before, during and after their activity, says Hemingway. “Don’t forget to hydrate before – that’s really important.”

Another guide is to look at the colour of your urine. This should be a pale yellow – not darker and not completely clear either.

And don’t forget the most obvious strategies of avoiding exercise in the heat if possible, adds Hemingway. Consider if outdoor activity can be done in the early morning or night time, when temperatures have fallen – or go to an air-conditioned gym.

المصدر: iNews