Technical: the Desert, Water And You
TECHNICAL: THE DESERT,WATER AND YOU
Arid, Dry and Hot This Place. The Motorcyclist More Than Anyone Should Know His Bodily Needs to Avoid Disaster
J. G. Krol
HAVE YOU EVER undertaken strenuous and extended physical effort in a hot, dry climate? Then you’ve probably experienced hypohydration, even if you didn’t recognize it for what it was. For a motorcyclist, a long race or enduro through the western deserts is the condition most likely to cause hypohydration, but any vigorous cow-trailing during the summer months burns enough water that hypohydration can strike anyone, anywhere in the country.
At best, the victim may suffer lethargy and exhaustion, which he probably attributes to being out of shape. At worst, he may die from lack of water, and at least one such case has been reported in the motorcycle press. The most common effect of mild hypohydration is to impair the rider’s physical and mental ability, possibly forcing him to drop out of a race by choice or by crash. The problem is serious enough in California desert races that there is some current talk of requiring each rider to carry a canteen of water.
Surprisingly, most dirt riders know very little about hypohydration...and most of what they do know is wrong.
For example, most riders say “dehydration” to describe a deficit of water, though this implies the removal of all water, leaving the body the consistency of instant coffee. The more accurate term, introduced by space scientist R.E. Johnson in 1964, is “hypohydration.” This means a lack, or deficit or abnormally low level of water in the body which, of course, is the situation that actually concerns us.
Normally the body is about twothirds water by weight. The proportion of water is ordinarily regulated within plus-or-minus a quarter of 1% of total equilibrium body weight. (All percentages will be given in terms of total equilibrium body weight.) Since a pint of water weighs just over 1 lb., this means that an average-sized man, free from thermal and physical stresses, will ordinarily regulate his body fluid within plus-or-minus one small bottle of Coke. The onset of hypohydration is usually taken as the loss of an amount of water equalling 2% of total equilibrium body weight. Hypohydration in an averagesized man begins at a water deficit of 1-2 quarts. With a water deficit of 2% he’ll experience some loss of efficiency and a fair amount of discomfort.
A water loss of 10% causes marked discomfort, clear bodily symptoms, and a considerable loss of physical efficiency, endurance, strength and speed. However, these effects are completely reversed when the lost water is replaced. Experiments demonstrate that 10% hypohydration has no permanent aftereffects, even if it is repeated many times.
The maximum tolerance for hypohydration varies somewhat among individuals, depending' on attitudes, motivations and emotions at least as much as on physiological differences. Ambient temperature is very important, too. In temperatures below 80-degrees F one might be able to survive as much as 25% hypohydration, but a 15% water deficit may prove fatal above 90-degrees F. Note the double effect of temperature—the hotter the air the more water is lost, and yet tolerance for such losses is lower.
In ambient temperatures above 92-degrees F the body absorbs heat from the air and sun faster than it can radiate heat back out. This places the full burden of regulating body temperature on evaporative cooling-sweating— which means water loss. As you know, it is essential for motorcyclists and other mammals to regulate their body temperatures within quite narrow limits. Heat exhaustion, sunstroke, heatstroke, and heat prostration are the names variously given to a group of related disorders characterized by collapse, coma and death, and stemming basically from a loss of control over body temperature. This will happen when so much body water is lost that a person can’t sweat enough to continue providing the necessary amount of evaporative cooling. From the viewpoint of temperature regulation, a 10-degree increase in air temperature from 80-degrees F to 90-degrees F is much less significant than a 10-degree increase from 90-degrees F to 100-degrees F. The latter increase reverses convective and radiative heat transfers so that heat flows into the body by these means, and it requires that the body obtain all cooling by evaporation of sweat.
Temperature control is easier if the body is covered with light clothing than if the skin is bare. That is, more cooling per unit of water evaporated is achieved, or less sweat is lost for a given degree of cooling. This works out automatically for motorcyclists, who have to wear some clothing to protect against abrasions, anyway. Dirt riders also benefit from being up off the ground on their machines. On a hot day, it is 30-45 degrees cooler a foot above the ground than it is right on the deck.
On the other hand, the very nature of dirt riding prevents taking advantage of two main ways of cutting water loss-staying in the shade and limiting physical exertion. The more active one is, the more internal heat generated, hence more sweat has to be evaporated to get rid of this excess heat. Thermodynamically, this is just like a car that runs cool cruising on level roads, but overheats when developing extra power to pull up a long hill. Moving along in the open on a bike is a mixed blessing. The breeze helps to evaporate sweat, so the rider stays dry—he won’t be drenched with sweat like a àewer cleaner. But this also means a good deal of water can be lost without ever being aware of just how much he’s really sweating. In this way, hypohydration can sneak up on a person.
Since you can’t avoid the conditions for hypohydration, be prepared to recognize it when it does occur. Table 1, based on Physiology of Man in the Desert by E.F. Adolph and Associates, gives a list of symptoms roughly in order of increasing hypohydration. Some of these, like increased rectal temperature and decreased blood volume, require special instruments to measure, but most of the symptoms can be observed simply by looking and questioning. According to the table, a person is in rather serious trouble by the time fingernails and lips begin to take on a bluish coloration. What is not so obvious is the role of thirst, which is listed as the very first symptom of hypohydration. Seemingly, thirst would increase in some approximate proportion to the degree of hypohydration. But due to a quirk of the human water metabolism, this is not true.
(Continued on page 99)
Continued from page 81
It appears amazing that a racer or enduro rider who lavishes any effort or expense on improving the capabilities of his machine, who jogs a mile a day to keep his body in shape, who invokes all the competitive tricks and advantages he can find, would willingly throw away a good fraction of his strength, stamina and speed by allowing himself to become hypohydrated. But this is exactly what happens and it’s not at all unique to motorcyclists.
Out of all the experiments with, and medical observations of, hypohydration that have been made over the last century, one finding emerges clearly: Nobody does and nobody can drink water fast enough to replace sweat as he loses it during hard work in hot, dry climates. This phenomenon has been named involuntary hypohydration by physiologist John E. Greenleaf. It is caused by what might be considered a breakdown, or overload, in the thirst mechanism. Think of it this way. You can easily hypohydrate 5% during a few hours of vigorous riding. If you normally weigh 160 lb., that means you’ve lost more than a gallon of water. Have you ever tried to drink a gallon of liquid at one time? If you try to force it down, chances are you’ll vomit it all right back up. This is a normal reaction and, if more water is available, you can drink a more moderate amount again and it will stay down. When your water deficit exceeds a couple of quarts you will not feel like drinking—will not be able to drink in one sitting—enough water to replenish the entire loss. This is involuntary hypohydration.
The thirst mechanism is not well understood even today. Various hypotheses have been advanced to determine perceived thirst from one or another single cause. Attempts have been made to explain thirst in terms of the proportion of water in the blood or in the intercellular fluids or within the body cells; in terms of the concentration of salts in these fluids; in terms of the volume of water swallowed at one time or the volume of water in the stomach; in terms of the activity of the hypothalamus, the air temperature, or the levels of physical fitness and physical exertion. Unfortunately, perceived thirst seems to depend on all these factors, so no simple explanation is possible.
Perhaps the most worrisome finding of such studies is that as the temperature goes up the amount of water one feels like drinking goes down. This means high temperatures are a triple threat—they increase the rate of water loss, they diminish tolerance for hypohydration, and they interfere with the thirst signals that tell one to replace the lost water. This can be a vicious circle. On a hot day a person may, without realizing what he’s doing, permit his water deficit to continue at a high level, or even to increase, because he just doesn’t feel like drinking.
For reasons no one clearly understands, man seems to be unique among the species in his susceptibility to involuntary hypohydration (all species are vulnerable to hypohydration, of course). A hypohydrated dog, for example, will not only recover his entire fluid deficit with a single drink up to 5,-min. long, he will actually overshoot his normal water balance by 15% or more. There is a certain logic to this. If he’s just suffered a major water loss, it’s likely that the same thing may happen again. If so, he’ll be better prepared for it if he starts off with a surplus of water in his body. Other animals like laboratory rats, rabbits, mourning doves, cats, oxen and, naturally, camels can and do replenish their water deficits with a single, lengthy drink. Man cannot do this. Severely hypohydrated men offered unlimited amounts of water will usually drink no more than a single pint at one time.
Ordinary water intake is at a rate sufficient to replace the entire supply of body moisture over a period of weeks. If a motorcyclist spends Sunday riding the boondocks, he will surely hypohydrate to some degree. For the next 3-5 days he will have to drink more than usual in order to overcome this deficit. Whereas some animals can replace their water losses in a matter of hours, or even minutes, it takes man 3-5 days to regain his water balance after an episode of hypohydration. Following a Sunday of vigorous dirt riding it will take most of the rest of the week to catch up on water supply.
Folklore has it that a person can acclimate to high temperatures and adjust to hypohydration. In general, this just isn’t so. Here’s what actually happens. During the first day of strenuous activity in the heat of the day, he loses water as he sweats, more or less proportionally to his activity and to the temperature above 92-degrees F. If he drinks an amount guided by his thirst, he will not drink enough to replace the water losses as they occur. This leaves him hypohydrated. In the evening, the temperatures will be lower and he, presumably, will be less active, so the rate of fluid loss will be lower and his drinking will tend to make up part of his water deficit.
If he repeats this cycle day after day his water intake will tend to adjust to accomplish three things. First, he will slowly overcome his initial deficit. Second, his average daily intake will rise to equal his average daily losses. And third, his hour-by-hour drinking pattern will tend to shift towards his hour-by-hour losses, i.e., he will tend to drink more during the hottest part of the day and during the periods of greatest activity and sweating. Even so, there will remain some degree of periodic hypohydration during and following peak daily activity and temperature. (Continued on page 100)
Continued from page 99
This whole process of adjustment takes 10 days-2 weeks, and it is the only sense in which he acclimates to strenuous activity in high temperatures. All that really happens is his water intake comes into closer balance with his water losses. Acclimatization does not mean that he loses less water or that he needs to drink less water or that he can develop greater physiological tolerance for water deficits. On the contrary, it means that he learns to increase and regulate his water intake throughout the day, minimizing the extent of hypohydration at any point in time.
A weekend rider will not enjoy this physiological adjustment that takes place over a couple of weeks of regular daily activity. As far as water metabolism is concerned, each Sunday is a “first day” of hypohydration. He can, however, make certain psychological adjustments. Having experienced some degree of hypohydration on several previous occasions, he will know what to expect and can be mentally prepared for it.
Don’t underrate mental preparedness; it is an important factor in many other aspects of motorcycling. A novice rider is likely to panic the first time he accidentally slides the rear wheel. Even some pretty good riders freeze up if they inadvertently lock the front wheel and cause it to slice while descending a hill. Both will probably be spit off. A more experienced cyclist on the other hand can often ride out the same situations, simply because he knows what to expect and stays calm. Early one spring I rounded a turn on Saddleback Mountain and saw a patch of snow on the trail—it must have been all of 20-ft. long and 6-in. deep. I was so terrified I didn’t even know what it was until I tasted it in my mouth. Yes, Virginia, I was lying face down in the snow. No, Virginia, I didn’t plan it that way. A motorcyclist who’d ridden in snow before would have sailed through this snowpatch effortlessly, and probably thought it fun. It’s all a matter of psychological preparedness.
Besides ensuring a calm and sensible approach to such symptoms of hypohydration as one may experience, psychological preparation forewarns a person that he will actually need more water than he feels like drinking. Experiments with lumberjacks, soldiers, cane cutters, construction workers, and the like usually find that, at first, these men think they need less water than they really do, and that they try to prove how rugged they are by denying their thirst even to the extent it is perceived. Strangely, the same subjects who pride themselves on how little water they need often pride themselves on the sizes of their appetites, that is, on how much food they need. If one is mentally prepared, he will realize that, due to involuntary hypohydration, he needs even more water than his thirst would indicate, so he will drink freely and often, just as much as he comfortably can.
There is some evidence that people who are born and raised and live all their lives in the Sahara, Arabian, Gobi or North American deserts do adjust to hypohydration. This is not to say they need less water or can go longer without drinking, only that a given percentage of hypohydration does not seem to upset their body chemistry quite so much. More importantly, such desert people invariably adopt life styles that minimize their water losses by rationing their sweat. They rest quietly and stay in the shade during the hottest part of the day. This isn’t the way the movies show it, but in hot weather Arab desert caravans travel before 10 in the morning and after 5 in the evening. If the moon is bright, they travel at night and spend the day asleep or at rest. Thus, a good part of the legendary adaptation to hot climates is behavioral, not physiological.
Motorcyclists too, can make such behavioral adaptations, at least to a limited extent. If they’re going out for a full weekend of cowtrailing, they can do most of their riding in the morning and afternoon, spending the hot midday lounging around camp, eating a leisurely lunch, taking plenty of water with the food, and trying to impress their buddies with bench-racing stories and tall tales of derring-do on the trails. During the hottest months of the year, an increasing number of desert races are scheduled to start just after dawn, avoiding the peak daily temperatures. This is a good idea, but it’s not entirely under a rider’s control. Things are tougher if the race starts late in midmorning, or if it’s hundreds of miles long, or if it’s an enduro that takes six, eight or even ten hours to complete. In these cases he’ll be riding during the hottest part of the day, and should be prepared for higher levels of hypohydration.
In hot, dry climates a minimum of about one gallon of water per day is needed, even if a person does little but sit still in the shade. The more active one is, the more water he needs. Riding hard throughout the hot part of the day increases his requirement to two or even three gallons per day. That’s right, gallons. He will be hard pressed to drink that amount of liquid. Indeed, he should drink more, and more often, than his thrist seems to require if he wants to keep up with his rate of water loss. Studies conducted in 1945 in various hot, humid climates (hot and dry climates being even worse) found that none of the subjects drank enough to keep up with his sweat losses completely, and that thirst did not seem pressing until considerable hypohydration had already occurred.
Table 2, also based on Adolph’s book, is a guide to the length of time one can expect to survive at various temperatures and low humidity. Notice how little advantage a quart canteen of water really provides. For extended exposure, one has to think in terms of gallons per day, not quarts. On a gallon of water per day one can walk about 20 miles per night, resting in the shade while the sun is up. That’s a fuel consumption of 20 mpg, comparable to a 750cc two-stroke.
Does this mean carrying a quart canteen is pointless? Well, if a person expected to be afoot in the desert for days or weeks, a single quart of water wouldn’t make much difference one way or the other. But a canteen of water can make a considerable difference when trail-riding with friends or competing in an organized event. Table 2 assumes the person is starting off with a normal water balance. Actually, if he’s forced out of a race or enduro by heat and hypohydration he probably is, at that point, already 5% or more low on water. Once down, he has to spend some time waiting for help to arrive. Since a canteen represents about 2% of his weight, it can reduce his existing hypohydration by two percentage points...or it can keep hypohydration from getting two percentage points worse. That could mean the difference between staying awake and alert alongside the trail, and wandering off in a daze or falling asleep in a patch of shade somewhere off the trail where the cleanup crew will fail to see him as they sweep the course.
Aside from its fairly limited physical benefits, a canteen of water can be highly valuable psychologically. If one is dizzy, nauseous and uncomfortable, a few swallows of water can make him feel a lot better. Knowing that he has some water left helps him to wait patiently for the cleanup crew and to avoid doing dumb things like trying to walk out without having any clear idea of the distance or direction to go. For these reasons he’ll probably want to drink his water a little at a time, so there’ll be a little more available for as long as possible. Knowing that he can take another drink if he absolutely has to is psychologically beneficial—even though there is no purely physical advantage to rationing his water to a swallow at a time.
On most bikes it’s fairly easy to nestle a canteen among the fork tubes and triple-clamps, holding it in place with a couple of bungee cords. Finding a way to carry more water on the machine is not so easy. A canteen can be carried on a cartridge belt around the waist. The disadvantages of this are that the weight pulls the rider down, the canteen flops up and down and tends to slide around the body to the worst possible position, and as sure as God made rocks and cacti, he’ll eventually fall on it. If water is carried on the waist at all, use two canteens, not just one. Besides the obvious advantage of doubling the water supply, the balanced weight tends to ride more smoothly (assuming the rider drinks from the canteens alternately) and the belt doesn’t have as much tendency to turn around the waist, placing the load in an awkward position. Arrange the canteens so they are back behind the hip bones. A simple but often overlooked trick for minimizing damage to the body when falling is to use cheap plastic canteens instead of solidly built, military surplus, metal ones. The plastic canteen will burst on impact, acting as a shock absorber, whereas a sturdy stainless steel canteen will drive right into the body, maybe rupturing the spleen. Of course, if the rider never falls, the metal canteen should be chosen for its durability.
Don’t overlook the most obvious place of all to carry a supply of water: in the body. Be sure to drink plenty of water for several hours in advance of a race, so as not to set out already hypohydrated to some degree. And just before leaving the starting line, drink as much water as can be comfortably tolerated in the stomach. If carrying one canteen on the bike, then drinking a pint of water just before each forray from camp effectively increases the on-board water supply by 50%. More than a pint will probably produce a sloshy stomach and interfere with riding.
If cross-country racers are each required to carry a quart of water, as has been proposed, it won’t make a great amount of difference to the individual rider. He won’t get significantly farther with his canteen than without it. Perhaps the most important benefit of this proposed rule would be that several other riders, whose machines are running well and who don’t need water badly themselves, could supply a good deal of water to the occasional competitor who is forced out with severe hypohydration at some remote spot on the course.
What’s actually needed is not so much a new rule as a better way to carry water on a dirt bike. Herewith are some suggestions to enterprising accessory manufacturers:
(1) A combination water tank and number plate that would quick-disconnect between the forks and fill the hollow between the triple-clamps. It should be possible to double the capacity of a canteen here if the tank is efficiently shaped.
(2) A tank of about two quarts capacity that quick-clamps to the handlebars and to the handlebar crossbrace, or that clamps solidly and has a drinking tube.
(3) A saddle-tank that attaches to the frame loop that holds the rear fender behind the seat. This wouldn’t work on some bikes, of course, but it would place the added weight in the most favorable location. It would make sense for the really long races through hostile terrain and for extended trail riding.
(4) A kidney-belt with a pair of suitably located, non-flopping canteen pouches built in. This would be a big improvement over the usual cartridge belt that slides around and allows the canteens to pound up and down. A kidney-belt circled by soft, flat plastic water pouches would be even better, if it could be made sufficiently durable, and would greatly enhance protection for innards in case of a fall.
So far we’ve been talking only about water. But it isn’t just water that the body loses when one sweats, nor is pure water the only fluid one can drink. One line of argument, which everyone has probably heard, is that the body loses salt as it sweats, so a rider had to take salt tablets to make up this loss. Also, salt tablets make one feel thirstier, which will lead to more drinking, which is good. There is some truth in this, but also a lot of myth. Involuntary hypohydration—the failure to drink as much as is needed to replete a water deficit—can happen when water is lost without losing salt, when salt is lost without a proportionate loss of water, or when salt and water are lost together. The former can be replaced by means of salt tablets, but ordinary table salt is not the only salt the body needs; potassium chloride, for example, is also necessary. As a person sweats, the salt concentration may go up in some body fluids, down in others. Excessive salt consumption can depress thirst rather than stimulate it, thus increasing involuntary hypohydration. And the most striking consequence of excessive salt consumption is that should one manage to raise body salt above normal, he will require additional water to purge it from his system; this means an increase in hypohydration.
Salt water, alcohol, gasoline, blood and urine are ineffective water substitutes because they contain chemicals that must be purged from the body, and it takes the kidneys more water to remove these foreign substances than is provided by drinking the fluids in the first place. The kidneys require more than a quart of water to flush out of the system the amount of salt ingested by drinking a quart of seawater. So drinking seawater increases hypohydration. Brackish water, however, provides some net gain in water after the kidneys remove its impurities.
After profuse sweating, some extra salt is needed, but the amount is not terribly critical. At mealtimes there will probably be a heightened craving for salt on food. Salting meals more heavily than normal approximates the amount of extra salt needed due to sweating. Sprinkle it on and don’t worry farther about the matter. Some people have been led to believe they should force down salt tablets, even to the extent it makes them nauseous. Forget it. That much extra salt isn’t needed. It would be better to force down more water than one feels like drinking, instead of more salt tablets than one feels like eating.
(Continued on page 102)
Continued from page 101
One can’t go wrong by drinking pure water, but some studies have shown improved water retention if the liquid is nearly neutral on the acid-alkaline scale (pH about 6), if it contains a fractional percentage of chlorides (salts), and if it is fortified with glucose (sugar). The liquid should be fairly cool to make it palatable, but it should not be ice-cold. Ice-cold liquids remain longer in the stomach. Since water is absorbed through the walls of the small intestine much faster than through the stomach walls, ice-cold drinks take longer to reach the bloodstream where they’re needed. If an ice-cold drink seems to satisfy your thirst better, this is another instance of involuntary hypohydration. Vigorous exercise right after drinking also delays stomach emptying.
So acidic beverages like tea or coffee are not ideal. Tepid, sweetened, weak tea is preferable to ice-cold, acidic lemonade. Soft drinks containing real sugar are preferable to dietary soft drinks, but the carbonation of such beverages makes them difficult to drink in the necessary volumes. Beer and wine are less effective than plain water, because only part of their water content is a net gain. And good old Gatorade is as close to an ideal drink as is commercially available today...but ignore that stuff in the advertising about drinking it over ice. That’s okay if you’re lounging on your patio or watching football on TV, but it’s a whole different ball game when you need to get several quarts of water into your body as quickly and efficiently as possible.
The most important single thing to remember is that thirst is not always a dependable guide to the amount of water needed in order to regain normal water balance. High temperature, low humidity, and strenuous physical activity all combine to depress thirst, causing involuntary hypohydration. Yet these are the very conditions in which rate of water loss and degree of hypohydration are apt to be greatest. Consequently, under such conditions a person should more-or-less force himself to drink as much as he can as often as he can. He will still hypohydrate to some degree because of his inability to replace water as quickly as he loses it. Involuntary hypohydration seems to be an awkward, inconvenient, and potentially dangerous quirk in the human water metabolism, but awkward quirks or not, it’s the only metabolism we’ve got.
