With temperatures set to reach 34 ⁰C across some parts of the UK today, The Physiological Society – an association of health scientists – have set out some helpful advice to help you stay cool. But they also carry a word of warning: cooling off too quickly can be fatal.
Avoid all forms of heat, including exercise
Exercising in the heat puts extra stress on your body by increasing muscle blood flow and your body’s core temperature. The increased demand for skin blood flow in the heat can, especially if combined with dehydration, compromise muscle blood flow, reducing oxygenated delivery to the muscles and causing heat exhaustion. The heart also has to work harder to maintain circulation.
In hot weather it is important to reduce the risk of dehydration. Hydration maintains good cardiovascular function and helps your body sweat. This is essential to maintaining a normal body temperature. If you are hydrated, your urine will be a very pale straw colour pale. If you do not drink enough fluids, your urine will be darker in colour as your kidneys try to save as much water as they can.
Wear sunscreen to avoid sunburn
Any exposed part of your body, including earlobes, scalp and lips, can burn. Sunburn compromises skin circulation and sweating and can therefore limit the body’s ability to get rid of heat. In addition, the ultraviolet radiation absorbed by the skin from sunlight can also damage the genetic material in skin cells, increasing a person’s risk of skin cancer.
Artificially cool yourself with a fan
When we are hot, we sweat. Sweating helps us to control our body temperature because when sweat is evaporated into the air, it cools the skin. Fans speed up this evaporation process and increase convective cooling, helping us to maintain body temperature. You can further enhance evaporation cooling by wearing light and lose clothing and misting your body with water.
Immerse your hands in cold water
Our hands have a high surface area-to-mass ratio and specialist blood vessels in the fingers that have high blood flows in the heat making them ideal areas for exchanging heat with the environment. When hands are immersed in cold water, heat can be quickly lost from the body and lower body temperature.
Why trying to cool down too quickly can be fatal
With today’s hot weather, many people could be tempted to jump into the sea or an open body of water to cool off. However, sudden submersion in cold water can be fatal. Mike Tipton, trustee of The Physiological Society, and professor of human and applied physiology in the School of Sport, Health & Exercise Science at the University of Portsmouth has been researching the body’s response to sudden immersion in cold water for the last 20 years.
‘With today’s hot weather many people may be tempted to cool off in cold water. However, jumping into cold water (below 15 ⁰C) can evoke the “cold shock” response, which includes an involuntary gasp response followed by uncontrollable hyperventilation. This response is incredibly dangerous if you are in water because the 2-3 litres gasp is greater than the volume of water (1–3 litres) in the lungs needed to drown.’
We lose around 400 people a year to accidental immersion-related deaths, drowning rates go up during heat waves. Professor Tipton believes quite a lot of these deaths are avoidable if people understand some basic physiology.
‘Education = survival. The more people know about the cold shock response, the more they can take steps to protect themselves. We see the largest physiological response to immersion in cold water in the first 90 seconds. The cold shock response is greater if you enter the water faster. Therefore, the secret to survival if you must enter the water, is to do it slowly or partially.
‘If you find yourself in cold water, either intentionally or accidently after falling, resist the urge to thrash about or swim until the cold shock response passes. It is important to relax and float to keep water away from your airways until your breathing is back under control. Allowing your body time to adapt to the cold water will decrease the risk of drowning.’