Imprimir Republish


Body at the limit

Physical exercise protects the organism against damage caused by sleep privation

NEGREIROSIn 2003, a brief phone call put an end to months of searching by researchers Marco Tulio de Mello and Hanna Karen Antunes, from the Sleep Institute of the Federal University of São Paulo (Unifesp). Scholars of the effects that physical exercise produces on the organism, Mello and Hanna Karen planned an experiment to discover what happens with the body and mind of someone who spends days without sleeping. And they had almost everything necessary for the research at their disposal. All that was missing was to find people willing to spend some sleepless nights in the laboratories of the Sleep Institute – without receiving anything in exchange, since the Brazilian legislation precludes the remuneration of research volunteers. At the other end of the line, journalist Celso Lobo, from Rede Globo, presented the solution. A team from the Fantástico program was to report on the first Brazilian edition of one of the longest and most exhausting competitions in the planet – the Ecomotion-Pro, in which the participants spend days almost without sleeping – and he invited the team from Unifesp to monitor the athletes’ performance. It was the opportunity that Mello and Hanna Karen were pursuing so much.

After weeks of planning, Hanna Karen disembarked with almost half a ton of equipment in Lençóis, in the interior of Bahia, where she transformed one entire wing of one of the main hotels of this town of a mere 10 thousand inhabitants into a research unit. There, at the entrance to the Chapada Diamantina National Park, she submitted 11 competitors from three different teams to batteries of physical and psychological tests and analyses of their sleep before and after the trial. The first results of this experiment, repeated in another two editions of the Ecomotion-Pro and also on the premises of the Sleep Institute in São Paulo, are now emerging in a series of scientific articles that reveal how physical exercise can, up to a point, protect the organism from the harmful effects caused by the lack of sleep. It is useful information not just for athletes accustomed to submit body and mind to extreme situations, but also – and in particular – to improve the quality of life and the performance of people that work in very long or irregular shifts, such as doctors, nurses, aircraft pilots, bus drivers, policemen and firemen, amongst others, who add up to 15 million people in the United States.

The confirmation of the protective effect of physical activity became evident when Hanna Karen and the group coordinated by Mello compared the data on the almost 300 variables relating to the physical and mental health of the athletes with the wear and tear to which they had submitted themselves during the trial. For seven days and seven nights, the participants in the 2003 Ecomotion-Pro de 2003 covered 477 kilometers in the Chapada Diamantina National Park, one of the few preserved areas of the Cerrado in the country. They ran, they cycled, they climbed or rowed to cross fields with creeping vegetation and sparse trees, dense forest, mountain ranges, rivers and waterfalls. All this, without time to rest. Made up of four members, usually three men and one woman, the teams only slept when they could not stand any more – on average, they would rest half an hour each day. Besides the physical challenge, accentuated by the temperature variation that swung from 20° to 36°C in that month of November, this sporting modality, created in the 1980’s in New Zealand, imposes intense mental wear and tear of the competitors. The teams have to remain alert the whole time, to find the route to be covered with only the assistance of a compass, an altimeter, and a relief map of the region. “In this kind of competition, the slightest error of the athlete responsible for guiding the group’s movement, the navigator, usually results in an increase of kilometers in the team’s route. And in a lot of wasted energy”, Hanna Karen explains.

Just the effort of covering a distance similar to the one that separates São Paulo from Rio de Janeiro in one week would be sufficient to leave anyone physically exhausted. Then imagine doing all that without any shut-eye. Studies published in the last three decades have more than demonstrated that sleep privation leaves people aggressive and agitated, besides, of course, tired. It was precisely like that, exhausted and with alterations to their humor, that Hanna Karen expected to find the athletes who crossed the finishing line of the three editions of the Ecomotion-Pro that she accompanied. And it was, in part, what she found.

From the physiological point of view, the competitors’ organisms were very debilitated at the end of the trial. They would arrive with their feet badly hurt, cramps all over the body, and from 7 to 10 kilos thinner, because during the trial they would consume 3,500 kilocalories per day and would spend three times more. The blood levels of a protein that indicates lesions in the muscles and in the heart would about 20 times higher than normal, similar to someone who was suffering from a heart attack, and the rates of hepatic enzymes suggested a serious lesion in the liver. Amongst the men, the rate of the masculine hormone testosterone, essential for the restoration of the muscle cells, was found to be 70% below normal, a sign that the body had used the available resources to keep itself functioning.

But from the cognitive point of view, they were fine, much better than could be expected from someone who had been without sleep for almost a week. They would remember the difficulty of climbing a rock wall or of reencountering the way through a stretch of dense forest after getting lost at night. They were also neither sad nor irritated. “It was surprising”, Hanna Karen says, “they would arrive happy for having finished the trail and they would recount the adventures through which they had passed with an impressive wealth of detail”. One long night of sleep lasting from 16 to 19 hours was enough for them to recover almost completely. Even before returning to São Paulo and analyzing the data, the researcher already imagined that the physical exercise was responsible for this well-being. But it remained to discover how sedentary people would respond to sleep privation for such a prolonged period. She also wanted to know whether the fact of showing good physical conditioning was sufficient to prevent the damage associated with the lack of sleep, or whether this benefit would only favor those who practiced exercises during the time they were awake.

With their eyes open
In the laboratories of the Sleep Institute, coordinated by physician Sérgio Tufik, one of the principal specialists in sleep disorders in the country, Mello and Hanna Karen decided to reproduce the trial in the Chapada Diamantina. Of the 28 volunteers invited to this stage of the research, eight were sedentary and 20 carried out physical exercises frequently and had already taken part in competitions like the Ecomotion-Pro. Fourteen athletes exercised themselves on apparatuses that simulated the modalities practiced and the distances covered in the 2003 Ecomotion, always carrying the same equipment that they took in the competition. The athletes would manage to complete the tasks in roughly four days, in which time the other volunteers had to keep themselves awake with reading, films, board games or videogames and browsing on the Internet. Those who did no exercises could only sleep, actually take a snooze that would last little more than one hour, when the physical activity group decided to stop to rest – and for the same time. “The sedentary people would try the whole time to convince the athletes to rest for a few minutes”, Hanna Karen says. The volunteers who did not do exercises would spend a good deal of the experiment amusing themselves with a car racing videogame in which they would manage to surpass several stages of the contest and spend hours in front of the television. “At the end”, the researcher says, “they were no longer capable of getting past the first curve”.

To evaluate the quality and the pattern of the sleep, Hanna Karen and Mello repeated polysomnography examinations before and after the experiment and during the snoozes. On the first night when they could sleep as much as they liked, the volunteers who exercised themselves during the four days showed an increase in slow-wave sleep, a stage in which there is a greater production of growth hormone, essential for cell multiplication and the restoration of organs. Only on the following night was there an increase in the sleep associated with the recovery of the cognitive functions, the so-called REM (Rapid Eye Movement) sleep, when the greater part of the muscles of the body remain paralyzed and dreams occur. Those who remained awake without doing exercises, though, showed an increase of REM sleep already on the first night. “This alteration in sleep pattern seems quite logical”, Hanna Karen comments, “first the organism recovers the body and then the mind, in the cases where the physical wear and tear was greater”.

Hormonal fluctuations
The benefits of exercise became evident when they analyzed how the levels varied of two hormones: testosterone, connected with muscular recovery, and cortisol, released by the suprarenal glands in situations of stress like an armed robbery or a competition. Both those who exercised themselves and those who let their muscles rest while that looked for another way of keeping awake showed a decrease in the testosterone rate, also associated with sexual desire and erection. Previously identified by biophysician Monica Levy Andersen in studies with rodents at the Sleep Institute, this reduction was more marked amongst sedentary volunteers.

Cortisol varied in a more complex way. It used to be believed that the level of this hormone would be higher in the group that exercised itself during the experiment, since sleep privation and the excess of physical activity are different sources of stress, and each one of them brings about an important increase in the release of cortisol. Different from what was expected, the active volunteers showed an initial increase followed by an important reduction in the rate of the stress hormone, which remained high amongst the sedentary. “There is possibly a security key that prevents an exacerbated increase in the level of this hormone”, Hanna Karen comments. It is as if the body knew the moment to lower the production of cortisol and so prevent the depletion of its reserves of cholesterol and of other hormones essential for the functioning of the organism.

More importantly, after the first night of rest, the level of cortisol had returned to normal, amongst the volunteers who had done exercise, while amongst the sedentary this only occurred three days after the experiment, on average. “Despite being more tired, those who kept themselves physically active recovered more quickly”, Hanna Karen says. “These results suggest that exercise triggers physiological and neurochemical responses that work as an antidote to the losses caused by the sleep privation”, Mello says.

It is now known that spending the small hours wide awake or working up to a day and a half to conclude a project whose deadline coming up does not cause any great damage to the organism, which rapidly re-establishes itself. The problems arise when what ought to be an exception becomes the rule and now repeats itself year after year, the case of doctors and nurses who are used to working in shifts of up to 36 hours when they are on duty. The consequence of this inadequate rest pattern is an increase in cardiovascular problems, like high blood pressure and heart attacks. To combat these harmful effects, it is calculated that three 50 minute sessions of exercise a week would suffice.

But there is a limit. Physical exercises seem to combat these damages in the situations in which one remains no more than 96 to 120 hours (four or five days) without resting adequately. After so much time awake, the best thing to do is to sleep. That is because after this stage the levels of irritation and failings in the memory and physiological unbalance become so intense that physical activity fails to protect and now merely masks the problem. “We are trying to identify this tenuous limit that separates the protective action of exercise from the masking effect”, Hanna Karen says.

At the same time, Mello and another researcher from his team, Márcio Rossi, attest to the effect of aerobic exercises (swimming and running) and anaerobic exercises (bodybuilding) carried out at different moments of the day on the sleep pattern of the sedentary. The objective is to discover what is the most adequate kind of physical activity for workers who need to stay awake during the night or for long periods, such as doctors, policemen and truck and bus drivers. Before the end of this year, the team from the Sleep Institute intends to put to the test different exercise programs, in experiments with workers from the nuclear power plant of Angra dos Reis, in Rio de Janeiro, and from Petrobras’s oil platforms, who work in irregular shifts. In Mello’s opinion, physical activity may represent a cheap and efficient way of helping these people, without the unwanted effects caused by stimulants (coffee, guaraná powder and energy drinks) or medicines. Besides combating the effects of sleep privation, these professionals could benefit from other effects now known, such as strengthening of the muscles, hormonal balance and an increase in the cardiac and respiratory capacity.

Before people go out there running through the parks or in search of a fitness center, Hanna Karen warns that this physical activity cannot be random and must take into consideration the characteristics of each person – how many hours a day he sleeps, what the quality of sleep is like, and what period of the day he works in. On the basis of this information, they next try to find the most adequate exercises for each worker, who must be accompanied by a doctor and be given guidance by a professional in physical education.

Sleep and sex
Despite the evidences of the protective effect of exercises, more and more data is building up about the harmful effects of sleep privation. Recent experiments conducted by the team of Monica Levy Andersen, from Unifesp’s Sleep Institute, indicate that the losses from the sleepless nights affect the male and female sexes differently. A few years ago, Monica showed that in male rats sleep privation affects the functioning of an area of the nervous system associated with pleasure and causes an effect called hypersexuality, an abnormal number of erections and spontaneous ejaculations, which is not necessarily good (please see Pesquisa FAPESP nº 110). Now, Monica and biophysician Isabela Beleza Antunes have proved that the privation of REM sleep, when the brain is just as active as when in waking hours, alters the reproductive cycle of female rats.  After being taken out of a tank with water in which they remained four days almost without sleeping, keeping their balance on dry platforms, the rats would go nine days without ovulating or menstruating, according to an article published last year in Hormones and Behavior. In human beings, this time would correspond to two interrupted menstrual cycles – roughly two months. “This data suggests that the lack of adequate sleep may be one of the factors associated with the difficulty that some women show in getting pregnant”, Isabela says.

The researchers observed this alteration whenever sleep privation occurred at a specific moment in the estral cycle of the rats (equivalent to the menstrual cycle in women), known as diestrum – when the uterus is getting ready to receive the eggs released by the ovaries. Without resting fully, the rats produced levels of the corticosterone hormone, corresponding in rodents to the human cortisol, twice as high as normal. The excess of this hormone leads to a greater production of the sexual hormone progesterone, which controls the functioning of the ovaries. And more progesterone, in turn, means a lower production of two other hormones: the follicle-stimulating hormone (FSH) and the luteinizing hormone (LH), responsible for the ripening of the eggs. “Menstruation only comes back when the rates of LH and FSH returns to normal”, Isabela explains.

The damage caused by the lack of sleep may be even more serious. After the menopause, the period in which the ovaries stop producing the estrogen and progesterone, sleep privation increases the risk of cardiac problems. Rats that undergo a surgery to remove the ovaries, a situation similar to the menopause, show a risk 20% higher of developing cardiovascular problems than those that remain with the reproductive apparatus intact and were also unable to sleep. Monica and Isabela already expected some increase in the risk of cardiovascular diseases, since the estrogen acts as a protector of the cardiovascular system. But they did not imagine that it would be as high as what was observed in the study published in January in Behavioural Brain Research. According to Monica, the probability of the females without ovaries suffering from heart problems became practically the same as in males, where it is naturally higher. “We believe”, says Isabela, “that stress associated with the lack of sleep reduces even more the level of estrogen, increasing the cardiovascular risk”.

The Project
Sleep Studies Center; Modality: Research, Innovation and Diffusion Center (Cepid); Coordinator: Sergio Tufik – Unifesp; Investment: R$ 16,403,545.87 (FAPESP)