Operating in extremely hot conditions creates a unique set of medical risks. In the link is the medical outline – for non medics, regarding those risks from the Namibia Ultra Marathon training guide.

DEHYDRATION
Dehydration is the most common heat related illness – in fact, it is thought that dehydration could be the single greatest threat to the health of an athlete. When training regularly and for long distances, fluid intake should be made a priority. You must drink fluids all day – not just during training. 

Don’t depend on feeling thirsty to tell you when to drink. Thirst is a late response of the body to fluid depletion. Once you feel thirsty, you are already low on fluids. The best indicator of proper fluid levels is urine output and colour. Ample urine that is light coloured to clear shows that the body has plenty of fluid. 

Dark urine means that the body is low on water, and is trying to conserve its supply by hoarding fluid which means that urine becomes more concentrated (thereby darker). 

Dehydration can be the cause of feelings of fatigue or exhaustion – at all times watch out for signs of dehydration and take on water regularly through out the day. 

Signs of dehydration are as follows: 

• fatigue
• dizziness or confusion
• headache
• decreased urine output and a darkening of colour
• heartburn or stomach ache
• recurring or chronic pain
• lower back pain
• dry or sticky mucus membranes in the mouth
• mental irritation or depression
• water retention
• lack of skin elasticity
• sunken eyes 

Fluids & Salts:
Another factor in overall fluid balance is the replacement of salts lost to sweat. Sports drinks contain carbohydrates and sodium which will help you to replace lost electrolytes. When training long distances, and during the race, you must bring sports drinks containing sodium to be included in your fluid intake to ensure you remain suitably hydrated. 

Prevention:
Your body absorbs fluids best when you drink frequently and in small amounts rather than drinking large amounts at one time. It also helps with fluid absorption if you drink while eating. To ensure proper hydration, drink regularly throughout the day, begin drinking small amounts of water (about 8 fl oz) at least 30 minutes before you begin training, then drink another 8 to 12 fl oz immediately before you begin your activity. During training, you should drink 6 to 12 fl oz of water or sports drink around every 15 minutes. Finally, drinking after exercise is a must to ensure you replace lost fluids. 

Treatment:
The best way to treat dehydration is to prevent it from occurring. If you suspect excessive fluid loss during the race, take a rehydration solution, walk and contact one of our race doctors as soon as possible.

HEAT EXHAUSTION
One of the most common health problems amongst extreme adventure competitors is heat exhaustion. When the body is unable to cool itself through sweating, serious heat illnesses may occur. Symptoms of heat exhaustion are: 

• Intense build up of heat in head – causing severe headaches, dizziness or light headedness. In extreme cases the sufferer may faint.
• General confusion or inability to think straight
• Loss of muscle control and weakness of the body
• Extreme tiredness, upset stomach, vomiting
• Pale, clammy skin and excessive breathing 

Prevention: 

To help avoid heat exhaustion, it is recommended that you
• Drink plenty
• Wear light, breathable clothing
• Slow your pace to adjust to the heat
• Take frequent, short breaks to allow the body to cool down
• Avoid alcohol or beverages with caffeine. These make the body lose water and increase the risk for heat illnesses. 

Treatment:
If you think you or another runner is suffering from a heat-related illness during the race, find a cool and shaded spot, lie down with your feet elevated and contact one of our doctors immediately. If heat exhaustion is left untreated, it could lead to heat stroke. Symptoms include nausea, dizziness, goose bumps, extreme fatigue, weakness, weak and rapid pulse, heavy sweating, uncoordinated stride or vomiting. 

EXPOSURE (HYPOTHERMIA)
There can be a dramatic drop in temperature in the Namib Desert after the sun has gone down. This will leave you at risk of being exposed to the cold and could even leave you in danger of getting hypothermia. 

Hypothermia occurs when the body loses heat faster than it can produce it and the core temperature of the body falls. It is surprisingly easy to progress from very cold to dangerously cold due to a combination of wind, wet clothing, fatigue and hunger, even if the air temperature is above freezing. Cold conditions are exacerbated by wind where the temperature is effectively lowered and it appears to be much colder than it actually is. This phenomenon is known as wind-chill. 

Symptoms of hypothermia are:
• Exhaustion
• Numb skin (particularly toes and fingers)
• Uncontrollable shivering
• Slurred speech
• Irrational or violent behaviour
• Lethargy
• Stumbling
• Dizzy spells
• Muscle cramps 

Prevention:
Managing mild hypothermia is relatively easy, as long as you have the correct protection from the environment. It is best to dress in layers; silk, wool and some of the new artificial fibres are all good insulating materials. A hat is important, as a lot of heat is lost through the head. A strong, waterproof outer layer is essential, as keeping dry is vital. 

Treatment:
If you or another runner is suffering from hypothermia, you must prevent any further drop in body temperature. Seek shelter and wrap up to insulate yourself. Replace any wet clothing with dry ones; make sure your head, feet and hands are covered; drink warm drinks if possible and eat high energy foods (sweets, chocolate etc). Get into your sleeping bag – with another person if possible to help you warm up. 

Namibia Ultra Marathon
Across the Divide
Desert Medicine Training Course – Namibia

Most of my diving has been in cold water. Not just the American definition of cold water, being anything less than 18ºC, but properly cold! UK winter diving of 5-6ºC for example, or Arctic Russia and Antarctic winter diving with sea temperature down to -1.8ºC, together with air temperature down to -20ºC. 

 
Perhaps it’s the splendour of travelling to dive by skidoo, ice particles glinting in reflected sunlight all around, breathe freezing on the scarf around my neck. Or is it the battle with the elements, when spindrift snow enters every crevice of clothing and covers the newly cut ice-hole. Or the continuous struggle to keep equipment warm and dry, to prevent freshwater ice from entering then regulator and causing a free-flow. Excitement is present with every dive, senses ready to detect the first rattle of ice forming in the regulator, a pull on the rope to signal a problem, or the eerie whistle of a seal singing beneath the ice!

Diving during the Antarctic winter is an extraordinary experience and I feel very lucky to have had this rare opportunity. The Antarctic continental land exhibits extremes in physical characteristics and severity of climate. But underwater, seasonal sea temperature fluctuations are minimal, often varying only between +1 to -2ºC, making Antarctic waters one of the most thermally constant environments in the world. These cold waters, however, have a vast seasonal change in nutrients, providing abundant summer food to an array of marine organisms. Summer diving may resemble diving in pea-soup during plankton blooms, but in winter the visibility allows spectacular diving conditions. As the sea freezes, wind no longer stirs up the surface. Sea ice restricts light filtering to the water beneath, limiting plankton and algal growth. Particles settle out of the water column, icebergs ground and become fixed in the frozen surface. The challenge of SCUBA diving in these conditions includes drilling or chain sawing an ice-hole, protecting equipment against cold, keeping the tender on the surface warm against raw winds and freezing temperatures, and working as a team to ensure safe underwater work, managing scientific instruments and cameras whilst wearing 8mm thick neoprene mitts!

Under-ice diving is becoming more accessible to the adventurous (or mad?!) diver as centres in Russia, Norway and Canada run ice-diving courses. When Expedition Medicine first discussed a course in Medicine for Marine Environments, I thought that encompassing this with under ice diving would be ideal! The idea didn’t last for more than a breathe, and anyone wishing to go on the course will be pleased to hear that it will be run in Oman – in warm water!

The aim of the course is to provide medical and expedition experience for doctors hoping to go on future expeditions. We’ll experience a desert environment, based in a bay beside the Arabian Sea, with local guides and camp staff for support. Geographically we’ll be about 2½ hours south of Muscat, the capital of Oman. The minimum requirement for diving on the course is PADI Open Water Certificate, and there is opportunity before or after the course to gain further dive experience or qualifications at one of the Omani PADI Dive Centres.

We aim to provide an unforgettable experience of the marine environment, using daytime sessions of practical skills and lectures in the evenings, to enhance your understanding and enjoyment of the marine environment, and to enable you to be a bonus to any expedition. Fitness to dive, diving equipment, water rescue, boat handling, search and rescue techniques, dangerous marine creatures, sea kayaking…and more!

The course speakers have a vast range and depth of experience. Dr Mark Reid is an expert on marine animals and has previously worked alongside Steve Irwin. He has organised and led many diving expeditions. Mark Hannaford, Managing Director of EML is a power boat instructor, Director of Across the Divide Expeditions and leader of many desert expeditions. Rob Conway is a doctor form London, working at the Mayday Hospital London, who is also the founder and medical advisor for Blue Ventures. I have experience in diving Medicine from the hyperbaric units in both Aberdeen and Plymouth, and have conducted diving research whilst working in the Antarctic. I hope to give lectures on decompression illness, decompression theory, and under-ice diving!

Oman is a safe and friendly country that welcomes western visitors. Dress requirements are m ore relaxed than many neighbouring countries, and head cover is not required for women outside mosques. The rugged interior contains mountain ranges contrasting dramatically with desert plains and interspersed with lush valleys. The coastline is over 1000 miles long, with areas where mountains plunge directly into the Arabian Sea.

Oman offers the best diving in the Gulf. Underwater visibility consistently ranges between 15 – 25 metres. During October, the air temperature should be a pleasant 25-30ºC, but several degrees cooler at night. We will be staying in tents, with meals provided by local cooks. Sea temperatures are expected to be between 24-28C, thus probably only requiring a 5mm wetsuit. During the summer months (April to September), as the sea temperature rises, a 3mm wetsuit would suffice.

The range of marine life is amazing! There are a large number of endemic corals that have learnt to survive in sea temperatures above their normal temperature (over 30C during summer!). We hope to sea Spinner dolphins on the surface, and beneath the waves the colours will amaze you! Coral varieties include Table, Brain, Stag and Teddy Bear corals; several varieties of moray eel – Zebra, Honeycomb; sharks such as Lemon and Black-tip Reef sharks; turtles, lobsters, Sting Rays, Eagle Rays, sea cucumbers, octopi, sea slugs, various sea anenomes, Barracuda, Blue Triggerfish, Spotfin Lionfish, Blue Tang, Cornetfish, Parrot Fish, – to name only a few of the myriad species!

So, if you’re one to get excited about diving a new environment, and want to learn expedition techniques whilst enjoying an exotic location, come and join us!

Dr Lesley Thomson

Is a lecturer on Expedition Medicine’s Polar Medicine and Diving Medicine Training Courses