Thursday, 25 July 2013

Keep your body cool.....

Hate travelling on the tube in this heat and want to know how to keep cool.  I know I do!!!  Tubes are unbearable in this heat even when it is getting a bit cooler....  I wish we had air con on the tubes.  Here are some things that will help you cool down. 

Dr Michael de Podesta is someone who knows a thing or two about high temperatures. He’s a researcher at the National Physical Laboratory, the government centre responsible for all temperature measurement standards in Britain.

‘When we eat, most of the energy from food ends up as heat,’ he says. ‘This means someone eating 2,000 calories a day needs to lose heat at a rate of 100 watts to maintain their core body temperature.

‘At the moment, the sun’s intensity is approximately 1,000 watts per square metre. So stay out of the sun if you want to stay cool. It’s hard to lose 100 watts of heat when the sun is adding hundreds of watts.’

De Podesta says heat is taken away from the body by air. ‘Your body warms up the air next to your skin and if that air moves, it then carries the heat away with it,’ he says. ‘Your body then warms the next parcel of air around it and so on. This is why a breeze makes you feel cooler, as it’s constantly taking heat away from the body.’

But it’s a problem when the air temperature is the same as that of your skin. ‘Your skin temperature is between 25-30C,’ he says. ‘And when the outside temperature is the same, it’s very hard to lose heat. At that temperature, a fan will need to be on very fast to take the heat away. ‘If you use a fan and your skin is hotter than the air, it will eventually cool you down.’

De Podesta suggests placing your fan near an open window in the evenings. ‘As the outside temperature cools, you will be able to get some of that external air into the room,’ he says.

We all know what happens we get too hot – we sweat. Our bodies contain millions of sweats glands and, on average, every day we produce one litre of the stuff. As sweat evaporates from our skin, it absorbs heat from our body and that’s what cools us down.

Chris Flower is a biologist at The Cosmetic Toiletry and Perfumery Association (CTPA), which represents the people we go to when we sweat too much.

‘There are actually two different types of sweat glands,’ says Flower. ‘Apocrine glands are largely in the armpits and groin areas and these react to emotion (such as stress) and temperature. Although they are linked to heat, which is why we sweat most in our armpits, these glands are not very useful in terms of keeping us cool.’

Eccrine glands, however, are found all over the body and these are the ones that control temperature. This makes us different to most other animals, adds Flower. ‘Dogs, for instance, use panting to cool down,’ he says.

Most of the time, eccrine glands produce what’s called ‘insensible perspiration’ because we aren’t aware of it. ‘They produce a tiny amount of sweat all the time but this increases when we’re warmer,’ says Flower. ‘When we get warm, the thermoregulators (the nerve endings in the body that sense temperature) switch on perspiration to cool us down. As this water on the surface of the skin evaporates, it uses heat energy and eventually brings our temperature down.’

Flower adds that we shouldn’t panic too much in this hot weather – most of the time the body does a pretty good job of cooling itself down. ‘Our bodies are very good at keeping the right temperature,’ he says. ‘Feeling hot and flustered is as much of a state of mind as the body itself isn’t overheating.’

Our bodies have another trick for cooling us. ‘When you’re hot, blood rushes to the surface of the skin,’ says Flower. ‘And the little capillaries in the skin open up to allow more blood through. This allows your body to lose heat.’

So how to keep cool? ‘Drinking plenty of liquid will allow the body to sweat more, as this replaces the lost perspiration and allows the body to keep perspiring to cool down.’ But despite most of us opting for a cold drink over a hot cup of tea, it’s not advisable to just drink iced drinks. ‘You might be able to trick the body into cooling down by drinking a hot drink but if you drink too many iced drinks you actually cool the core of your body and the thermoregulators think you’re not warm enough, so instead of having all the blood at the surface to radiate heat out, it actually draws it back in and you conserve it,’ he says.

Another trick Flower suggests is running cold water over your wrists. ‘There are lots of little blood vessels on your wrist and these will keep the blood cool,’ he adds.

Lastly, is there any hope for those travelling on the Tube or public transport? ‘Not really,’ says de Podesta. ‘Any kind of air movement will help you cool down but it’s generally best to avoid the Tube.’

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