9	Body Temperature, Electrolytes, and Running

Body temperature varies throughout the body. It is lost by physical processes and by physiological factors which enable the blood to be cooled as it flows through near the skin and by providing water for cooling the skin by vaporisation.

When the air temperature is low, the blood vessels of the skin contract to diminish heat loss; when the temperature is high, or when exercise produces excess body heat, they dilate. More perspiration is secreted and evaporative heat loss is greater. The more you exercise, the more blood flows through the outer skin area and the more you perspire.

Strenuous exercise creates a demand for more blood for the muscles and for more to flow to the skin for cooling; the warmer the atmosphere, the greater the demand becomes. This pressure can exceed the capacity of the heart to increase cardiac output, causing nausea, dizziness and even heat-stroke.

If you are not accustomed to exercising strenuously in heat, you are immediately exposed to these progressive problems: heat cramps through excessive loss of salt and water, which leads to neuromuscular breakdown; heat exhaustion, through circulatory inadequacy caused by dehydration; and, at the worst, heat-stroke, a condition serious enough to kill because the temperature-controlling centre of the brain becomes deranged.

You can adapt yourself to exercising in the heat by carefully controlling and gradually lengthening exercise periods while the circulation of blood to the arterioles in the skin improves in response to the stimulation you are giving it.

Marathon runners are often required to race in hot conditions in which body temperatures rises to extremes and dehydration is excessive. If they have been training in the heat, they can usually handle these conditions quite well but those unaccustomed to heat rarely finish and are often in a distressed state of fatigue for some time afterwards.

Jim PETERS’ marathon run in the 1954 Empire Games in Vancouver is probably the classic example of a fine marathon runner who came close to death through dehydration and circulatory failure because he was not prepared to compete in high heat.

People taking their first sauna bath usually feel extremely hot and even faint in temperatures of around 80°C but, over a conditioning period of a few weeks, can comfortably withstand temperatures up to 120°C.

The body’s temperature-regulating mechanism is most efficient, as I have proved during marathons in which I have been suffering from the effects of heat. Instead of using the customary sponge, I would up-end a bucket of water over myself. The cooling effect was almost instantaneous and allowed me to run freely again. I found I could run my regular marathon-training courses ten to fifteen minutes faster on cool days, which proved the degree to which the metabolism is taxed in hot conditions.

I have seen athletes trying to reduce weight by running distances on hot days in heavy clothing. They will certainly deplete their bodies of water and minerals but, because they are limiting the volume of running they could do by overdressing, and they will not be burning as much fat as they might hope. A few hours after stopping, they will have replaced most of the liquid they lost and their weight will be pretty much where it was earlier.

If they wore less clothing to keep the body temperature down and then ran farther and more intensely, they would be using up some of the fat in their bodies.

Another factor they overlook is that heavy clothing, by causing higher body temperatures, draws blood from the working muscles to the skin for emergency cooling, so the efficiency of the working muscles is reduced. Since it is necessary to do as large a volume of running as possible to develop general cardiac efficiency, anything that gets in the way is to be avoided. Wear only the clothing that is necessary; any more retards movement, overheats the body and reduces running’s benefits.

In high temperatures, even near 40°C, you can continue steady running for an hour or more, as long as the humidity is also high, and the moisture perspired can remain on the skin surface to help cooling. If the humidity is low, the perspiration evaporates quickly and creates conditions for dehydration.

When I tried a run in Tucson, Arizona, the temperature was 38°C and the humidity less than 20 percent. I lasted about 20 minutes and then decided I should stop. But, for six weeks in Maracaibo, Venezuela, at sea level and 10 degrees from the equator, I trained regularly for at least an hour a day. The temperature was always high – between 38 and 50°C – and I ran in the middle of the day, when everyone else was having a siesta, on the tarmac of an old airport. I could even do speed training for a full hour. I suffered no ill effects because the humidity was always near 90 percent and I was always wet with perspiration. I followed this programme to accustom myself to the heat so that I could sleep more easily at night when it remained extremely hot.

A study of runners after the 1968 Boston marathon and the United States Olympic marathon trial showed body temperatures were up to 41°C, and wider research revealed that it was not unusual for temperatures to be higher than 40°C after races of beyond six miles (ten kilometres). It was considered then that part of the distress seen during the final phase of a distance race might well be attributable to the stress of excessive body heat on the nervous system – a state of hyperthermia.

Little can be done about the environment but it is obvious that the runner must slow his or her pace to minimise the detrimental effects of a warm, sunny day. Most runners fail to allow for the weather hazards when they are racing. Taking fluids frequently helps the body’s air conditioning system; every ten to fifteen minutes is desirable, according to some researchers.

The first symptoms of hyperthermia occur at about 40°C body heat: throbbing pressure in the temples, cold sensation over the trunk. If the temperature climbs a little higher, muscular weakness, disorientation and loss of equilibrium follow; higher still, and diminished sweating and loss of consciousness occur.

At the point where you experience that throbbing in the temples allied with chills, you should stop immediately and try to lower your body temperature with cold fluids or cool showers. To continue is dangerous.

The opposite applies when you train in sub-zero temperatures. If there is moisture in the air when temperatures are 20 to 40°C below, it can become impossible to train because you risk icing your lungs. But, if the humidity is below 20 percent, you can train in those temperatures for hours, as long as the wind is not too severe and you are well wrapped up. As I explained in the chapter on clothing, I trained in Finland in two tracksuits which gave me a cushion of body-warmed air to run in. A woollen hat, muffler, gloves and socks protected every other part of me except my cheeks.

Remember the formula if you live, run or train in an area of temperature extremes: when the temperature is high, the humidity needs to be high; when the temperature is low, the humidity should also be low. If any other combination prevails, be careful of running into trouble. Limit your training.

The hazards are surprisingly real and too many have been caught by them. Recently, in bush not far from New Zealand’s capital, Wellington, three young runners died of exposure. They ran a short distance into the bush following a regular jogger’s trail, but encountered a sudden dramatic temperature drop, rain and hail. They were lightly clad and were almost immediately in difficulties from which they could not recover, because no-one was near to help them. They were dead before they knew what had happened to them.

The human body is a machine which works at 37°C. The other areas can get much colder but the vital organs must stay at that constant temperature. If, in cold, wet and windy conditions, the core begins to cool and the cooling is not immediately checked, you will suffer mental deterioration, loss of co-ordination, unconsciousness and total failure of breathing and circulation. Within 30 minutes of the first symptoms, you can be dead.

Check the progressive warning signs: tiredness, cold or exhaustion; lack of interest, lethargy; clumsiness, stumbling or falling; slurring speech, difficulty in seeing; irrational behaviour; obvious distress; the cessation of shivering, despite the cold; collapse and unconsciousness; coma.

It sounds unreal and a sense of unreality is one of the warning signs. If you feel any of the early symptoms while you are running in cold, wet and windy weather or note them in a companion, you must act immediately to prevent further heat loss, begin warming and try to prevent loss of consciousness. Do not bash on and hope for the best because that can cause the rapid onset of more serious stages. You must get out of the wind, get dry clothing, warm drinks and, essentially, send for expert help.

The best advice, of course, is to be adequately equipped with clothing to protect you against a sudden fall in conditions. And bear in mind that heat loss from the head is high – a fact often overlooked.

Over-breathing or hyperventilation is another unusual hazard. What happens is that, due to nervous tension, a person starts to overbreathe and blows off too much carbon dioxide. This gas is the stimulus to breathe and as the level in the blood drops, it causes biochemical changes which can lead to giddiness, pins and needles, rapid beating of the heart and a feeling of dread.

With most of the carbon dioxide breathed out, there is not enough gas in the blood to stimulate the breathing centres, breathing may stop and the victim may feel no desire to take a further breath. Then, because no oxygen is taken in, the level of this gas reaching the brain drops and this can lead to unconsciousness.

Then, as the level of carbon dioxide produced by the tissues builds up again, the breathing resumes and the person regains consciousness. Sometimes, the altered calcium metabolism in this phenomenon causes muscles to tense and twitch and hyperventilation can be mistaken for an epileptic seizure.

The remedies are to force a person under attack to slow down breathing or to breathe in and out of a paper bag, which forces him or her to re-breathe carbon dioxide and restores the balance.

However, exercise creates a surplus of carbon dioxide and uses up oxygen so it is a phenomenon not likely to be experienced by athletes except in rare circumstances. The outpouring of lactic acid into the blood contributes to heavy breathing and breathlessness but, by decomposing bicarbonate, also causes a temporary increase in the output of carbon dioxide.

Training in a warm climate or perspiring profusely, you have to replace minerals as well as lost water. In long-duration competition, such as the marathon, you should take liquids regularly before any effects of dehydration are felt.

Electrolyte drinks are now available – I recommend you take them at half the suggested strengths – which replenish lost minerals, but check that the one you buy contains calcium, magnesium and potassium. The reasons are discussed in the next chapter.