From the beginning of time, an amazing number of poets, prophets, preachers, politicians, playwrights, philosophers, etc., have found something noble, something glorious, even something heroic to say about human sweat. The book of Genesis equated it with life: "In the sweat of thy face shalt thou eat bread, till thou return unto the ground." Hesiod saw sweat as greasing the path to perfection: "...in front of excellence the immortal gods have put sweat, and long and steep is the way to it, and rough at first." Longfellow raised sweating to an essential American virtue in The Village Blacksmith:
His brow is wet with honest sweat,
He earns whate'er he can,
And looks the whole world in the face,
For he owes not any man.
And Thomas Alva Edison revealed it to be the essential component in everything from the light bulb to the phonograph to the 1,091 other inventions he patented: "Genius is one percent inspiration and ninety-nine percent perspiration."
Sweat has been romanticized, glamorized, dramatized, yea, canonized over the centuries. Of all the precious bodily fluids, only blood and tears have had a bigger play. But things have changed drastically in the last three decades or so, and sweat's reputation has taken a turn for the worse. In the old days an ode to sweat was really a hymn to the practice of honest, hard physical labor as well as a paean to the more hard-nosed, puritanical elements of the human character—perseverance, endurance, determination, a never-say-die will to succeed in the face of insuperable odds. Sweat was a verity.
Nowadays we are talking most often about quite a different brand of fluid, about a sort of sweat that oozes out of the dark wells of anxiety. We are talking about sweat produced by guilt, depression, insecurity, by bad marriages, bad news, bad dreams, bad checks, bad tempers, bad vibes, bad luck. We are talking about sweat that breaks out and soaks people who are sitting still in cool rooms. We are talking about nervous sweat, about sweat produced without physical exertion and without hot weather. We are talking about the brand of sweat that has given us a deodorant and antiperspirant industry which last year sold $860 million worth of creams, sprays, sticks, pads and powders.
George Sheehan, the physician-guru of running, wrote with fierce passion in his book The Runner about the phenomenon of sweat in the late 20th century: "I can put up with Madison Avenue using athletes to promote beer and cigarettes and even men's perfume, but when I see athletes in commercials for antiperspirants and deodorants, I rise in protest.
"It just makes no sense. The athlete wants or needs no antiperspirant, no deodorant. He is a hitting, throwing, running, jumping advertisement for sweat. Good honest sweat. The kind of sweat that made America and now has virtually disappeared from the country. The kind of sweat that went down the drain with the advent of an affluent technology and the rise of the service industries. The kind of sweat that was eliminated when our occupations turned from action to conversation....
"For this kind of sweat you need no deodorant. Honest sweat has no odor...."
Well, as sometimes happens with Sheehan. his enthusiasm has driven him into flights of hyperbole. The difference between honest sweat and the other kind isn't really smell any more than it is honesty. The good running doctor is quite wrong to imply that "honest sweat has no odor," as if there were some sort of dishonest sweat that reeks to the heavens. In fact, for most people fresh perspiration of any sort has no smell of its own. But Sheehan is absolutely correct in what he identifies as the No. 1 cause for the demise of the brand of American sweat that some people rank right up there next to patriotism and prayer as things that Made This Nation Great.
Today the U.S. is populated in large part by a sedentary, office-bound, technology-oriented breed of worker who labors by means of paper, phones, business machines and various other items known as "managerial tools." No less than 70% of Americans employed in non-agricultural work perform service-oriented jobs, many of which require less physical exercise in a full day than our ancestors got from spending one hour on the porch swing after work. To capture the essence and to understand the extent of the change that has occurred in the amount of physical exertion involved in work, think for a moment about the sweat produced by the mighty blacksmith at his anvil and compare it to that of the mighty IBM systems analyst at his terminal.
Clearly the sweat in those two examples not only differs enormously in quantity, but also in quality. And therein lies what we might call the physio-psycho-socio-economic truth about sweat in late 20th century American society: It's more often produced by tension and anxiety—call it psycho sweat—or by voluntary recreational exertion—call it sport sweat—than it ever is by the actual jobs we do. Here we could launch into a discussion of the honesty of our society as mirrored in the honesty of our sweat, but let's skip the sociobabble over the moral function of our sweat glands and move smartly on to the physiological.
Now this is a subject of far more complexity and seriousness than one might imagine after a lifetime of hearing TV hucksters reduce the subject of human perspiration to alarm about underarm odor. Sweat—its causes, purposes and effects—is one of man's oldest concerns. Hippocrates, the 5th century B.C. Greek physician, knew that skin gave off an invisible vaporous substance, but he couldn't explain why or how. Nor did he realize that these vapors were closely linked to fluid sweat, the functions of which he understood remarkably well. Not until the great medico and student of anatomy, Galen, tackled perspiration in the 2nd century A.D. in Rome was the mystery of sweat partially unveiled. Having already stunned the medical heavies of his day with the discovery that the arteries are filled with blood, not air as was widely believed, Galen then revealed that the mysterious vaporous secretion was discharged continuously and involuntarily through the skin and respiratory orifices as "insensible perspiration" and that it took the form of a visible fluid, sweat, when the body heated up beyond a certain point.
After Galen's breakthrough, 15 centuries elapsed before anyone added anything markedly new about sweat. Then, in the 17th century, Sanctorius, an Italian physician, built a large metal arm balanced on a fulcrum. He placed weights equal to his body weight on one end of the arm and sat on a platform on the other end for hours at a time—his slow ascension proving beyond doubt that his body was losing weight through so-called "insensible perspiration." Sanctorius continued to perfect and expand on this experiment for 30 years. In 1687, Marcello Malpighi of Rome established the existence of the orifices in the skin, the pores, from which watery droplets flowed. In 1833, Jan Evangelista Purkinjè of Bohemia discovered sweat glands and their spiral ducts, and in 1922, Use Schiefferdecker of Germany determined that there are two kinds of sweat glands—the eccrine and the apocrine."
A Nobel Prize has never been awarded for scientific work on perspiration, but if there was ever a worthy candidate, it was the late Japanese physiologist Yas Kuno. After 30 years of intense experimentation and investigation with the loyal assistance of some 65 collaborators and technicians, Kuno published in 1956 a 416-page book entitled Human Perspiration. Though a portion of its contents has been proved erroneous by subsequent research, Human Perspiration ranks as the definitive work on sweat. As Kuno wrote of his years of work, "With regard to the study of perspiration, these three decades may rather be looked upon as a period of renaissance."
According to Kuno, "All the daily sweatings in man may be classified into two groups, the thermal and the mental or emotional sweating. Thermal sweating appears over the whole body surface with the exception of the palms and soles. Mental or emotional sweating usually apppears restrictedly on the palms, soles and axillae [the armpits]—although occasionally on other regions as well."
Also, according to Kuno, women generally sweat less than men, people who live in the tropics are able to sweat more than others, and "athletes perspire more easily and more profusely than untrained people, and this seems to be true also of workmen in hot mines or hot factories."
Moreover, according to Kuno, no animal sweats as efficiently as man: "The development of sweat glands and of the associated nervous apparatus has been most highly attained in man, so that human beings stand at the top of the animal kingdom in their ability to keep body temperature constant."
The human nervous and hormonal systems are so sensitive that changes of as little as .1° centigrade trigger the mechanisms, like sweat, that cool or heat the body. The basic, most critical function of sweat is its thermal action, the simple act of cooling the body when it becomes too hot, either because of high external temperatures or from physical exertion. As Kuno wrote, man has by far the most finely tuned cooling system of all mammals, which as a class have the most sophisticated such systems in nature. Even those animals that also have sweat glands—such as the horse, sheep, goat and monkey—don't have as well developed a heat-control apparatus as humans do. On a hot day, sweating animals will have higher body temperatures than usual—will be running fevers, in effect—because their sweat glands aren't capable of pouring out the vast quantities of water needed to hold their body heat at a constant, normal level.
Most mammals rely either on panting or heavy salivation to keep themselves cool. Instead of sweat glands, a dog has a relatively large mouth and tongue; moisture evaporates from the tongue and from the lungs through extra quick and heavy breathing. Lions and tigers routinely increase their respiratory rate from 10 breaths a minute on cool days to 80 or more in the heat of summer. Mice, which have small mouths and no sweat glands, cool off by first drooling saliva on chest and paws and then rubbing it over the rest of their bodies. Elephants, with a huge sweatless body and a small mouth that allows neither heavy panting nor much salivation, keep cool by loading up their trunks with water and squirting it all over themselves—a procedure that probably equals the human sweat system in efficiency, and certainly beats it hands down as an all-round fun cooling method.
Nonetheless, the human perspiratory system is enormously sophisticated and terrifically effective in comparison to all others. The skin is, in fact, the largest organ of the human body. And the skin is absolutely peppered with pores, which are mainly orifices for sweat glands.
The two kinds of sweat glands Schiefferdecker found in 1922, eccrine and apocrine, are enormously different, in origin, in purpose, in quantity and in quality. Let's begin with the eccrine glands, because they are far and away the more numerous, the more important and the nicer of the two. (As we shall soon see, the apocrine glands may have played a fascinating role in prehistoric human life, and they play an oddly important commercial role today because, interacting with skin bacteria, they're the major producer of the stink that keeps the deodorant industry going. But no one can find that the apocrine glands now perform any remotely useful function in the body's cooling system—or any other system, for that matter.)
There are eccrine glands on every inch of human skin, from two to five million of them, except for the lips and parts of the genitals. A German anatomist named Karl Friedrich Theodor Krause was the first to actually count them. He established in the mid-19th century that there were precisely 2,381,248 sweat glands on the human body, and if they were linked together into a single super-gland, they would occupy eight square inches of space. Though his exactitude was admired, Krause's census was later found to be, at best, approximate; the total varies considerably from individual to individual. Eccrine glands are present from infancy in the same number they will be in maturity. Thus, the density of the glands in the skin of a baby is eight to 10 times that of a full-grown person, and a baby's sweating system is almost as efficient in its first year as it will be in adulthood.
The eccrine glands are so essential to human life that without them most of us would be unable to tolerate temperatures higher than 80°F. Given any amount of physical exertion, a sweatless body could bake itself to death with heat stroke at much cooler temperatures.
Gil Gleim, chief physiologist at the Institute for Sports Medicine and Athletic Trauma at New York's Lenox Hill Hospital, explains the body's cooling system this way: "There's an area in the central brain, the hypothalamus, that senses the increase in the temperature of the blood caused by a change in thermal conditions. This part of the brain then sets up an excitation of the autonomic nervous system which controls involuntary functions such as blood flow, heart rate, the digestive system and all sweat glands. The brain's reaction causes sweat to be secreted from the eccrine glands. The body surface gets rid of heat in three ways—by radiating it off, by conducting it away through touching something cooler, or by convection when air currents move over the body and cool it. Sweating removes heat from the body when it evaporates due to a flow of air over the skin."
The principle of physics involved in sweat's acting as a body coolant is the same one that comes into play when water turns to steam. As James Watt could have told you, heat is needed to cause the transformation of a liquid into a gas in a teakettle, and the same process occurs in a human when body heat makes sweat turn to vapor on the skin. As Kuno wrote: "One of the most important properties of water, insofar as it pertains to biological systems, is its high latent heat of vaporization. This property is fully utilized in perspiration, as it controls the body temperature by withdrawing heat from the body by vaporization of water."
For every gram of water evaporated, .58 of a Calorie of body heat is used up. In this case, we are talking about a Calorie with a capital "C," or a kilocalorie, which is equivalent to 1,000 small "c" calories. A calorie is the amount of heat needed to raise the temperature of one gram of water 1° Centigrade. (When dieters talk of calories, they mean the large "C" kind.) A liter of sweat will dissipate about 600 Calories' worth of heat from the body during exercise, the equivalent of a temperature reduction of 50°F. in a person weighing 165 pounds. Strenuous exercise (such as running or cycling) in hot weather, can result in water losses of as much as two or three liters in an hour. One can even train to sweat better.
According to Dr. David Costill, Director of the Human Performance Laboratory at Ball State University, an athlete can tolerate a maximum water loss of 8½% to 10% of body weight. In a man weighing 145 pounds, that equals 14 pounds or about a gallon and a half. "However, that would be extremely severe," says Costill. "Anytime you dehydrate more than two percent of body weight it begins to affect your pulse rate, rectal temperature and your central nervous system. We measured the actual sweat losses of runners at the U.S. Olympic Trials in Alamosa, Colo. in 1968 and of Amby Burfoot when he won the Boston Marathon that year, and the most that I've seen lost, even in a marathon, is five percent to six percent or about three to five liters." Former Dodger Pitcher Don Newcombe, a noted sweater who had—and has—a far beefier build than any marathoner, claims that on one memorably hot summer afternoon in Montreal, while pitching in a minor league game, he sweated so much he dropped from 220 to 200 pounds. "It took three days of drinking beer to get the weight back," says Newcombe.
Gleim says that athletes are able to produce more sweat—and do it more efficiently—than average people because they ultimately "recruit" more sweat glands to work in the course of repeated training routines. "The same is true of people in hot climates," says Gleim. "They don't have more sweat glands; they simply have more of them working. Sweating can be an adaptive process in this sense."
Similarly, saunas and steam baths cause people to lose enormous amounts of sweat in a short time, but as with strenuous exercise, prolonged stays in such baths require acclimation. And one must beware of overheating; if there is no airflow in the bath, perspiration won't evaporate and the body won't cool efficiently. Despite widespread belief to the contrary, a sauna doesn't offer any real benefits to an athlete, with the possible exception of a jockey, wrestler or boxer trying to make weight. It may, in fact, be harmful. As Costill points out, "It's important to bear in mind that dehydration affects endurance. If you dehydrate in a sauna or steam bath, you decrease your body weight by three to four percent. Studies indicate that this means you also decrease performance in a 5,000- or 10,000-meter race by six to seven percent." Furthermore, says Costill, a sauna can't prepare an athlete for hot-weather competition. "The only way to acclimatize yourself to heat is to do the work under conditions of heat," he says. "You can't train in a sauna or steam bath. To become heat-acclimated, a runner must run in that heat for 90 minutes a day for eight days in a row at a fairly high speed."
Though most people think strenuous exercise is an automatic way to work up a sweat, that may not always be the case. Take swimming. Although tests made during distance events held in very warm water—in the Nile and the Amazon, for instance—indicated that endurance swimmers sweat while swimming, test results in cooler water are ambiguous. No one has been able to establish for sure if a swimmer sweats while performing in cool water. But whatever the water temperature, "the demand for cooling from sweating isn't as great while swimming as in dry-land exercise," Gleim says.
Whatever the conditions, men demonstrably sweat more than women, though this doesn't mean that women don't tolerate heat as well as men. Sweat pouring off a male athlete doesn't necessarily indicate that his cooling system is working better than that of someone who's only slightly damp. "If a woman's body remains moist, she's sweating sufficiently," says Costill. "Women appear to be more efficient in their sweating; they produce just enough, whereas men often sweat in excess of what they need. The disadvantage in heavy sweating, of course, is that you also have greater dehydration." Could there also be some truth to the old saw that animals sweat, men perspire, ladies glow?
Jack Galligan, vice-president of research and development for the Gillette Co., the manufacturer of Right Guard and Soft and Dri deodorants and antiperspirants, among other products, has an obvious, enduring interest in sweat. Galligan says that tests performed by Gillette have revealed that "the underarm glands in women are larger, yet men put forth a greater rate of perspiration per gland. On the average, a woman sweats 400 milligrams during a 40-minute test period under warm, humid laboratory conditions, while an average man will sweat 600 milligrams under the same conditions."
The fluid secreted from the eccrine glands is 99% pure water, and the rest is a mix of a little sodium chloride (table salt) and far tinier amounts of potassium, urea, lactate and glucose. It was once thought that sweating helped to flush wastes from the body, that sweat glands were in some way similar to the kidneys. Not so. In 1978 the U.S. Food and Drug Administration published a pamphlet based on hearings and research into ways of regulating the manufacture and marketing of antiperspirants. Among the FDA's findings: "While sweat contains measurable amounts of urea and lactic acid, the popular belief that sweating is necessary to 'purify' the blood in an excretory manner analogous to kidney function is not borne out by fact. Many people live in air-conditioned or other cool environments and suffer no ill effects from the fact that they sweat little or not at all." Kuno, too, found no evidence that sweating was a purgative, for the simple reason that "most constituents of sweat other than water are small in amount."
It's true, however, that the discharge of sodium chloride through sweating could be significant. As Gleim says, "In terms of its evolutionary development, the body has a far greater ability to conserve salt than to get rid of it. An average man will take in something like three times the salt he needs with an average diet. Sweating may be viewed as an aid to keeping the balance right." Costill agrees, saying: "I never saw a marathoner who took salt tablets. They don't need to. The kidneys are an adequate regulator of the body's salt levels provided the diet is a normal one. If you go out for hard exercise and produce a lot of sweat with salt, the kidneys sense this through the hormone system and just excrete less. Because of this, marathoners may not urinate for 24 hours after a race."
Therefore, salt tablets may be of no value to a healthy person, even when sweating excessively from exercise. However, Gleim believes there is a need to replace other elements such as potassium following exercise. He recommends fruit juice for this purpose. He points out that "ergogenic" beverages, such as Gatorade, will also do the trick, but that they are more expensive than juices.
Costill urges athletes to stick to plain water before and during exercise. He discourages the use of fruit juice—"too concentrated"—and pooh-poohs the usefulness of products like Gatorade. "If you listen to the claims of the ergogenic commercials, it's amazing how the human race ever survived without such drinks," he says. "Their concept is that since the body loses electrolytes in sweating, the ideal is to drink the equivalent of sweat to replace them. This is totally impossible. Besides, the concentration of electrolytes in the body goes up, not down, during exertion because of the loss of water."
Whatever an athlete drinks to replace what's lost in sweating, he's going to be faced with the fact that his body can't absorb fluids as fast as it loses them. Even the long-distance runner who "fluid loads"—consumes huge extra amounts of liquids before the start of a race—and stops for a drink at every aid station along his route will end up dehydrated at the finish line. And a lot of weekend athletes don't have the sense to take such precautions, even on a hot, muggy day. "Humans, unlike animals, don't have a good system for knowing when they need water," says Costill. "Many animals can dehydrate three or four pounds, but they'll immediately drink water to replace it. Humans have a sluggish system. We have to drink in excess of what we desire."
If a person suffers too much fluid loss, the sweating mechanisms begin to shut down to prevent further dehydration. Then body temperature rises and symptoms of heatstroke appear—high pulse rate, dizziness, shortness of breath, even delirium. At this point it's far too late to gulp down a cup of cold water—a cold drink, though preferable to a hot one, will only minimally affect an overheated body. It's time to get medical help, and fast.
Remember, we're still talking about eccrine glands, the nice sweat glands, which work at the behest of the heat-sensory elements of the nervous system. Thermal sweating is strictly involuntary and is more profuse on the face and upper body than elsewhere. It has no smell and no color and has nothing whatsoever to do with the dark and odoriferous underarm world. Indeed, eccrine sweat is so clean and fresh and invigorating that folks like George Sheehan don't even wash it off. As he writes in Runner. "Almost every day in the early afternoon, I change from my street clothes into my running gear and put in a sweaty hour on the roads. At the end of the run I towel off, put my clothes on and go back to work. No shower. Showers are time-consuming and can lead to a chill and all the complications thereof. Showers are also unnecessary if they are used simply to rinse a dilute odorless salt solution off your body."
Too true. Sheehan says that to stay in good odor, all a person needs is "a daily change of clothes and that old-time favorite, the Saturday night bath"—as long as one sweats only eccrine sweat.
Unfortunately, that isn't possible because of the apocrine glands, which are found in a relatively few places—mainly in the armpits and on the palms of the hands and soles of the feet. Although they are present at birth, they don't become active until puberty. Children sweat pretty much pristine eccrine fluid; they don't become deodorant or antiperspirant consumers until they are about 13 years old. And in old age the apocrine glands gradually become less active for reasons not clearly understood, but probably related to a decrease in sex hormones.
No one is quite sure exactly what these apocrine glands are all about. Their secretion process is slow and skimpy, unlike the constant cooling wash of eccrine sweat. For long periods they don't do anything at all, and they seem to be activated only by a particular section of the brain and nervous system. The apocrine glands usually begin to operate suddenly under conditions of anxiety, fear or mental stress, such as anticipation of pain. Says Sheehan: "These glands go into action at the instant of any emotional distress. They can be triggered by any crisis, be it at home or on the job.... The irony is that the apocrine glands are vestigial organs, which means that anatomists don't know why we have them. They have no apparent function in the human, but like the appendix we still have to contend with them. One way to contend with them is to get rid of the trigger mechanisms of fear and anxiety and guilt and apprehension."
Kuno, too, was puzzled by so-called emotional sweating, writing that certain "phenomena accompanying emotion, such as constriction of the skin vessels, goose skin and glycemia are identical with those appearing in the cooling of the body, but contrary to those induced by heating. It seems very strange that both [thermal and emotional] agents act in the same sense in the provocation of sweat." Kuno went on to point out that so-called cold sweat is the product of emotional or sensory stimuli. He found that what could cause cold—or emotional—sweat to rush to the pores of the armpits, palms and soles included doing complex arithmetic problems in one's mind, reading difficult books, "emotion created by unexpected news," uneasiness over the expectation of painful stimulation, and moderate pain sensations, such as a mild electric shock or touching a hot light bulb.
These are about as far as one can get from the hard manual labor that brings sweat to the blacksmith's brow. Yet some investigators believe that these apparently useless, anxiety-excited glands played a big role in human evolution. Galligan, for example, suggests that emotional sweating was once a significant factor. "If you take the skin and wet it, its coefficient of friction goes up," he says. "It's 8.5 times higher on slightly wet skin than it is on dry. So if you happen to be gripping something—a spear or a club or, say, a rock—and suddenly you notice a mastodon or a saber-toothed tiger charging at you, the sweat in your palms will give you a better grip on your weapon, won't it? Of course, if thermal sweat is added to this emotional sweat, the palm will become too wet, and the ability to better grip an object will be lost—as with a slippery tennis racket. Also, some emotional sweat on the soles of your feet will give you better friction with the ground that would allow you to run more quickly, to get off to a faster start and to avoid slipping in front of whatever beast or monster is chasing you. And the lubrication from sebum, an oily substance from the sebaceous glands found in the hairy areas under the arms and between the legs, possibly worked to ease friction and prevent chafing when running away from—or after—something. I think it's very possible that our ancestors survived back in the Stone Age because of apocrine sweat. The better our ancestors sweated, the fitter they were to survive."