Melissa Murphy

Summer is the perfect time to enjoy exercise but care is needed to prevent overheating.

Words: Melissa Murphy

With the holiday season rapidly approaching, many of us of exercising with renewed vigour at the prospect of our tiny bikinis. But with the Met Office predicting a high chance of a British summer heatwave, we need to ensure we stay safe when exercising in the sunshine.

It’s possible to carry on with your normal fitness routine during the summer but you need to pay extra attention to avoid dehydration and overheating. Before you can do that though, you need to understand the basics of how your body regulates its temperature.

The body’s normal temperature range is between 36 to 36.8 C. If your temperature rises above this, it disposes of the heat through your skin by sweating. However, if your temperature rises sharply or goes over 40C then your body’s internal thermometer could fail and you may not dispose of the heat quickly enough to be effective. If this happens you could suffer from a heat illness. Heat illness can be divided into three categories according to its severity: heat cramps; heat exhaustion and heat stroke.
Higher risk
Strenuous exercise in the heat carries a higher risk of heat illness because of the risk of dehydration. If you sweat excessively and fail to replace the fluids then you are likely to become dehydrated. This could then progress into a heat illness.

Our bodies are about 70 per cent water, and dehydration occurs when the normal water content of your body is reduced. A one per cent or greater reduction in body weight due to fluid loss causes dehydration, classed as mild, moderate or severe.

While mild dehydration causes few symptoms and can be easily treated by replacing lost fluids, severe dehydration can be life-threatening and requires hospitalisation. Thirst is not always a good indication of dehydration, especially if you are swimming, as being immersed in water can suppress the thirst response. The warning signs of dehydration include:

• Dry eyes, lips, mouth
• Dry or loose skin
• Sunken features especially the eyes
• Clammy hands and feet
• Dizziness
• Tiredness or confusion
• Low urine output or concentrated, dark urine with a strong odour
When athletes perform in hot climates they normally go through a period of climatisation. During this period they will train at a reduced intensity while their body adapts to the higher temperature. However, the changeable UK climate means we could suddenly be faced with Mediterranean-style weather overnight. But the good news is that dehydration and overheating can be avoided by taking a number of steps.

Humidity levels
The first step is to check the weather before going for a long run. Temperature is not the only indication of the conditions; you also need to take note of humidity levels. High humidity levels combined with a high temperature can be a dangerous combination. If you are working out in high levels of humidity, your body will start to absorb heat from the environment rather than losing heat by sweating. Your body’s only response is to sweat even more and if this fluid is not replaced it can lead to dehydration.

So exercising in these conditions is best avoided, as is exercise between 11am and 3pm, the hottest time of the day. Dawn and dusk are generally considered the best times for exercising outdoors. It is important to carry a mobile phone with you or ideally train with a partner, and always carry a water bottle. This is to avoid being unable to reach help if you do feel unwell.

Sunscreen is essential, regardless of the time of day you exercise. Sunburn can occur at any time and sunburnt skin will not be able to dispose of heat effectively, increasing the risk of overheating. Look for a sunscreen which protects against UVA and UVB damage and is water-resistant so your sweat doesn’t reduce its protection. If you are sweating heavily, it is best to reapply once an hour. Look for lightweight sprays or creams which do not block the pores and allow your skin to breathe.

Another step to take is to wear appropriate clothing. Your skin is your body’s mechanism for losing heat so anything which prevents this is going to increase the chances of overheating.

“The rule is to wear as little as possible,” says Dr Chris Byrne, exercise physiologist at the University of Exeter. You may feel self-conscious and prefer to wear a baggy t-shirt and long jogging pants but summer exercise is not the time for modesty. Shorts and a vest top will be your best bet as they leave a large amount of your skin bare.

The choice of fabric is also important in terms of how much you sweat and how you feel during exercise. Go for light rather the dark colours which absorb heat. Although you may think natural fibres such as cotton would be best this is not the case. “Cottons tend to get saturated easily. This means once the fabric has soaked up your sweat, it will become a barrier preventing the loss of any more heat,” says Dr Byrne.

Best fabrics
The best fabrics to go for are modern fabrics designed for sports that are light and use a mesh style. These fabrics ‘wick away’ the sweat from the skin to the outer surface of the fabric and then away from the body. This should result in a moisture-free garment that leaves you fresher and cooler. Many of these modern fabrics also have an anti-bacterial layer to reduce any odour.

Most of these rules also apply if you’re using a gym, although it’s vital to exercise in gym with adequate air-conditioning or fans. “Most gyms will ensure their suites are set to specified temperature, says Paul Lyons, fitness instructor at David Lloyd Leisure (www.davidlloydleisure.co.uk). Gym users should also follow the advice on clothing and also sunscreen if using any outside facilities.

Experts agree that the most effective way to avoid overheating is to reduce the intensity of your exercise. In hot temperatures, regardless of whether you are inside or out, you should consider reducing the intensity of your exercise routine. It is important to listen to your body, and if you are struggling or experience cramps or pains then stop and rest.

Last but by no means least, comes the issue of replacing lost fluids. Lost fluids can be replaced by drinking water although sports drinks are considered to rehydrate your body more quickly.

It is normally advised to drink plenty of water before exercising and to top up every 15 minutes during exercise. However, a recent study by Dr Chris Byrne looked at the performance of athletes in extreme heat. The study found that the amount of fluids consumed during exercise had no impact on performance or on lowering body temperature. “My study has controversial findings, but it showed no evidence to support that drinking during exercise makes you run faster or cool down more quickly,” he says.

Byrne adds: “In my opinion, the most effective way to reduce body temperature is to reduce the intensity of your exercise and drink when you feel thirsty.”
 
Dr Byrne’s study is at odds with the rest of the sports community,however. “This certainly goes against the grain,” says Paul Lyons. “I would always advise my clients to drink plenty of water before exercise, to carry water with them and top up every 15 minutes.”

So with a little bit of planning, you can make the most of the British outdoors and look forward to wearing that tiny bikini.
Top ten safety tips

1. Wear light-weight mesh clothing, ideally a vest top and shorts.
2. Drink fluid before exercising, carry a bottle of water with you and top up regularly.
3. Always wear a water-resistant sunscreen and re-apply every hour.
4. Avoid exercising during the hottest periods from 11am – 3pm.
5. Avoid running in hot or humid conditions. Ideally run with a partner and carry water and mobile phone with you.
6. If you’re not used to exercising in the heat, reduce the intensity of your regime.
7. Try to exercise in air-conditioned gyms.
8. Pay extra care if swimming outdoors – you can burn and get dehydrated more easily.
9. Try a tepid or lukewarm shower after working out. The water will convey the heat away from your body. Don’t have your shower too cold though, otherwise your skin will constrict and retain the heat.
10.  If you experience any signs of dehydration or heat illness during exercise, rest indoors or in the shade, drink plenty of water or a sports drink. Seek medical advice if necessary.