Send any comments to the maintainer Roger Caffin
The author is not a doctor, and readers are cautioned to seek proper medical advice before believing anything written here.
No responsibility can be or is taken for what the reader does.
Inexperienced walkers should always stay on the cautious side of things!
Further contributions welcome.
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We go walking for fun. Obviously physical fitness will affect how well we walk, but after that the single most important factor is probably water. Without enough water, we are in strife. If you have ever run out of water while walking on a hot day you will know just how crucial water is; if you haven't (yet), that's an (undesirable) experience in store for you.
While you have enough water you just sweat. But once you start to run low there three stages you go through. (Terminology varies: this is what we use.)
Heat Stress means you are getting a bit hot and bothered. You may be running a bit short on water and your performance will start to go down a bit. Organisations like the Volunteer Bush Fire Brigades recognise this as a problem and encourage all volunteers to carry water, and also provide basic training on how to recognise the symptoms in yourself or others. Heat Stress is not good for you, but many walkers will admit that they have often suffered from it a bit on a hot day. Some may even go so far as to claim you can get used to it. Strictly speaking this isn't correct, but certainly one can become 'heat-conditioned' and better able to handle heat. Experienced walkers often get used to recogising and handling the symptoms: once you realise you are a bit 'hot and bothered', you back off a little and make sure you stay within your limits. If possible, you also start drinking. Inexperienced walkers very often make all sorts of mistakes, including excessive drinking. More on this below.
Heat Stroke is far more serious. While you have enough water in your body you will probably just suffer Heat Stress, but you can run low, and that's when Heat Stroke starts. You know when you make the transition quite easily: you stop sweating, and your skin gets very hot. CAUTION: this is serious! A common symptom also met is that the sufferer feels he or she cannot get enough air, and starts breathing very fast, even panting. The sufferer usually feels dizzy as well. What has happened here is that the feedback loops within the body have temporarily broken down. Your breathing is normally regulated automatically to give you enough oxygen and to help cool your core by evaporation. When you run low on water the evaporation stops working properly, so the breathing ramps up to try to get more of it. It becomes a run-away process. This leads to hyperventilation and contributes to the dizziness. But you will have to be many kilograms down from your normal weight before this happens: usually over 4 - 5 litres of water short of normal. That is a lot more than many ever experience.
The recommended medical treatment for Heat Stroke varies, but lying down in the shade helps reduce the heat-dissapation demands being made on the body. Some 'experts' strongly recommend an ice bath and a quick trip to Casualty. Wouldn't we all love the ice! More realistically, this happens when you are in the middle of the bush and short of water, and other treatments are needed. If the patient is hyperventilating, talk to him and persuade him to start holding his breath. He may argue that he feels he is suffocating: persist gently. Get him to control his breathing down to a very slow rate. This will stop the hyperventilation, and also lower the basic metabolic rate. Wait until the patient really has slowed down and relaxed: this may take quite some time, half an hour or more. A small snooze may help a lot. Real success comes when the patient starts sweating slightly, but this may not always happen. Then you have to decide what to do next. You could try walking on slowly, watching the patient carefully. You could send some people off to find water. Or you could wait until the evening before moving on. I guess you could also use your EPIRB or mobile phone to yell for help, but that decision is up to you.
Just in case you are wondering, yes, the author has been through the Heat Stroke stage himself and with others more than once. It was not fun, but we all survived. In one case it took half an hour just to get the patient breathing normally. In another case a half-hour snooze worked wonders. In a third case we resorted to walking uphill for 100 m, then resting in the shade for 10 minutes - repeated many times. The key action in every case was to limit exertion to a low level to let the body recover.
If you don't heed the warning signs and try to keep going, the next stage is collapse. The author thankfully has little experience here, and is not going to waffle. However, it is worth knowing what can happen if you push too far. A marathon runner killed himself not so many years ago in a race by 'pushing himself through the pain barrier'. Basically, his internal organs all failed: they 'melted'. Part of the problem here is that you can lose common sense before you realise what is happening. While this does not happen too often here in Australia, the Park Rangers at the Grand Canyon in America have to rescue people regularly. These are usually young males who think they are too tough to take notice of the warnings about dehydration. It is a common saying there that people die with a litre of water in their pack: they just don't notice they are going downhill.
At the same time, you can drink too much water. A very recent and very dangerous idealogy has been created that you should 'drink as much as you can'. Quite a few runners have died this way - more than from dehydration it is believed. The section on hyponatraemia (meaning drinking water to excess) covers this. A recent (2004) race across Sydney saw two people collapse from hyponatraemia.
One of the more interesting topics which surfaces occasionally is salt. There are those who swear by salt tablets, and there are those who swear against them. There are those who swear by 'sports drinks' for the salt and other 'electrolytes' in them, and there are those who sneer at them. It should be noted that many sports drinks are in fact very unbalanced, mainly in having a serious deficiency of salt or sodium. Apparently the vendor companies feel thay can sell more of their product if it tastes more like lolly water than a serious electrolyte mixture. That figures. There are those who believe in the recent fad for drinking huge volumes of water, and there are those who never do it and think it is dangerous (which it is). So dangerous that the next section deals directly with it.
'Hyponatraemia': a potentially fatal medical condition brought about by drinking too much water.
How much water you should drink in a day? The short answer may be a lot less than many of the self-styled 'experts' have claimed. A recent editorial by Dr Noakes, Editor of the British Medical Journal and world authority on sports medicine and fluid consumption, in the British Medical Journal1 suggests the the current dictum that you should 'drink the maximal amount that can be tolerated' is horribly wrong and leads to hyponatraemia2. To quote:
'To date at least seven fatalities and more than 250 cases of this condition have been described in the medical literature.' The editorial goes on to suggest that 'In particular, exercisers must be warned that the overconsumption of fluid (either water or sports drinks) before, during, or after exercise is unnecessary and can have a potentially fatal outcome. Perhaps the best advice is that drinking according to the personal dictates of thirst seems to be safe and effective.' Apparently marathon runners have been trying to drink over 1 litre per hour, possibly over 1.5 litres, and up to 15 litres in a day in one case, as a result of the drinking craze.
This editorial stirred things up a bit in the medical area, and triggered some 'discussion'. In response to some opposition, he went on to write in the correspondance pages of that journal3:
Consider first the definitive series of studies undertaken in the Nevada desert during World War II (35). There, in one study (36), groups of army conscripts exercised during the day in desert heat for as long as they could, usually up to 8 hours, without any fluid ingestion whatsoever. During this time they would cover up to 34 km. At the point of fatigue, caused by 'dehydration exhaustion,' subjects exhibited the following symptoms and signs: They 'grew peevish and intractable; others walked in silence and were unresponsive.' All developed marked physical fatigue and ultimately became 'incapable of even mild physical effort.' Yet 'there were no obvious after-effects of dehydration. . . . We do know that man can suffer a water deficit so incapacitating that he can neither walk nor stand; yet he recovers his walking ability within a few minutes of water ingestion, and his feelings of well-being within half an hour or less after he begins drinking. With a meal or two intervening, his recovery is practically complete in 6 to 12 hours.'If these army subjects, who developed levels of dehydration twice as great as those usually measured in modern endurance athletes, were able to recover within minutes of drinking fluids orally, where did the idea arise that much lesser degrees of dehydration are (1) life-threatening and (2) must be treated immediately with intravenous fluids? (8)
The second body of evidence--also conveniently ignored--is that up to 1969, endurance athletes were encouraged not to drink during exercise (2,12). Yet there are almost no documented case reports of complications experienced by these athletes. Thus, the impressively titled review article 'Heat Stroke and Hypothermia in Marathon Runners' (37) mentions only one case of heatstroke in a competitive marathon runner, that of Jim Peters in the 1954 Empire Games Marathon in Vancouver. The reasons other than dehydration that explained Peters' only collapse in a remarkable competitive career have been described (38). Generations of competitive distance runners were, like Peters, able to set world records at a wide range of running distances without ever consuming anything (let alone maximal quantities) and without apparently suffering life-threatening complications (as is now frequently reported in those who drink too much). [The references may be found in the cited article3.]
This has two implications for bushwalkers. The first is that the current craze for a 'hydration bladder' with a hose over your shoulder and nipple to suck on is just that: a craze based solely on marketing spin, principally designed to transfer dollars from your pocket to that of the manufacturers. You simply do not need to drink that much that often. The second is that most of the 'sports drinks' may be useless at best and possibly dangerous at the worst. Discussion in the medical journal following the editorial included the following quote3, but more may be read in the original article:
'Current sports drinks have low sodium concentration relative to sweat losses at maximum sweat gland function. Thus, it may be safer to increase the salt content of sports drinks to protect athletes performing under high heat rather than discouraging adequate replacement of losses. An added benefit would be that less serious athletes performing under lower ambient heat would not over-consume beverages with a higher electrolyte content. Normally hydrated individuals would find the brackish taste of more salty drinks less palatable. Such an idea obviously works against the thrust of the beverage industry that seek to cajole us all to drink as much as possible of any fluid they produce' [His words, my emphasis].
It would seem that this area of medicine has been of interest to Dr Noakes for some time. Another very good paper by him is "Hyponatraemia in distance athletes". This is definitely worth reading.
Andrew Taylor of UNSW supplied a reference to a fascinating Invited Review by H Valtin in the American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, 2002. The Review is entitled "Drink at least eight glasses of water a day." Really? Is there scientific evidence for '8 × 8'? and goes on to document the author's search for any medical evidence to support the title. ('8 × 8' refers to drinking eight 8oz glasses of water per day.) Not only did he find no supporting evidence, but he found many documented examples of the hazards of hyponatraemia. It's quite a lengthy and thorough paper, as you might expect from an Invited Review.
In addition, the author of that review found two other common claims to be rubbish. The first rejected claim is that you are dehydrated when you start to feel thirsty; the second is the claim that the water content of tea, coffee and soft drinks can't be counted. In fact, the phrase 'severe water intoxication' is used in this Invited Review in all seriousness. Read the paper for yourself.
In 2007 the American College of Sports Medicine issued a lengthy Position Statement on the general subject of dehydration and hyponatremia, autghoredf by a whole bunch of experts, entitled Exercise and Fluid Replacement. It is fairly heavy going, and does cover the risks from severe dehydration at levels rather beyond what the avergae bushwalker will ever experience, but an interesting quote from it is thus:
Health problems in individuals can result from dehydration or overdrinking (consuming volumes greater than sweat losses). In general, dehydration is more common, but overdrinking - with symptomatic hyponatremia - is more dangerous. Dehydration can impair exercise performance and contribute to serious heat illness, and exacerbate symptomatic exertional rhabdomyolysis; while exercise-associated hyponatremia can produce grave illness or death.
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Exercise - associated hyponatremia. Exercise associated hyponatremia was first reported at the comrades marathon (45). Later, exercise-associated hyponatremia was reported in endurance runners (104), and since that time a number of participants from a variety of occupational and recreational activities have been hospitalized for this condition, with several having died (8,82,100,108). Symptomatic hyponatremia can occur when plasma sodium rapidly drops to ~130 mmol.L-1 and below. The lower the plasma sodium falls, the faster it falls, and the longer it remains low, the greater the risk of dilutional encephalopathy and pulmonary edema.
Despite several of the aurthors of this report have some financial links to various beverage companies, the Position Statement does not make encouraging noises about so-called sports drinks.
As mention in the Water page, this whole hydration myth has even reached the web chronicler of Urban Myths, Snopes.com, who has the usual amused and critical comments to make about it, and about the vested interests who would like to benefit.
It's always interesting to read some of the old classics to see what previous generations thought and did. Lawrence of Arabia spent a lot of time with the desert arabs during one war. He rode with them on raids - he thought he was leading them, but maybe they were just enjoying themselves? Anyhow, these guys were travelling huge distances by camel, unsupported. Lawrence tried hard to match them in toughness: this included matching them in drinking, but not in the sense you might expect! The problem (for Lawrence) was that the arabs would drink a huge amount of (possibly suspect) water at one well, then ride for two days in the desert heat without another drink - until they reached another well. They drank like camels, and only when their camels could also drink. That was their norm! I don't think they suffered from hyponataemia, but neither did they all die from heat stress. Many older walkers may remember being taught in the 50s and 60s to just drink at breakfast and dinner times: similar idea.
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1: British Medical Journal, vol 327, 19-July-2003, p113
'Overconsumption of fluids by athletes: Advice to overdrink may cause fatal hyponatraemic encephalopathy'
Dr Timothy Noakes, Discovery Health chair of exercise and sports science, MRC/UCT Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, Faculty of Health Sciences, University of Cape Town and the Sports Science Institute of South Africa
2. Hyponatraemia: in simple terms a reduction in the sodium concentration in the body to a potentially dangerous low level. Obviously, drinking 15 litres as one person did could cause this problem.
3. BMJ, 19-Aug-2003, Rapid Response section, from William B. Greenough III, M.D., Professor of Medicine, Johns Hopkins University School of Medicine, USA
3. 'Hyponatremia in Distance Athletes, Pulling the IV on the 'Dehydration Myth', Timothy D. Noakes, MB ChB, MD, The Physician and Sportsmedicine, vol 28/9, Sep 2000
4. '"Drink at least eight glasses of water a day." Really? Is there scientific evidence for "8 × 8"?', Heinz Valtin, Am J Physiol Regul Integr Comp Physiol 283(5):R993-R1004. This article contains 100 references to the popular press and scientific literature. As you might guess, he finds no supporting evidence.
© Roger Caffin 1/3/2002, 31/01/2011