Ideally, the only reason why a healthy person should take to their bed is because what he or she has in mind cannot comfortably be undertaken by standing up. Bed is a superb place to sleep and have sex. What bed is bad for is rest and recuperation. Even though bed is still commonly prescribed for a cold, flu, or other minor ailments, hospitals continue to use a bed as the standard convalescing piece of equipment. There is reason to regard it as a positive hindrance to a speedy recovery.
When we're in bed, and especially when we're in bed on our own, we degenerate. Physically, that is—not morally. Even healthy people, when resting in bed, will experience degeneration of their bodily functions and develop a condition that is serious enough to be called "bed disease." Of course, there are some medical conditions that require bed rest, or placing the body in a horizontal position; but normal rest can be obtained without going to bed.
Cape Kennedy Physiologists Study Sleep
The recognition of bed rest as a harmful factor was a direct spinoff from the Apollo space program. Until the Cape Kennedy physiologists began their intense research into the effects of gravity on the human body, there were only two minor studies on bed rest, and the value of this treatment had been more or less taken for granted traditionally. Most of what we knew about bed rest was learned, after all, from people who were already sick. Even the most virile of lovers were not staying in bed long enough to give doctors an example of what happened to a healthy corpus if it was allowed to languish in a horizontal attitude.
Weightlessness sleep in decreased gravitational environments is the key to bed rest effects. When you are standing erect, it causes blood to pool in your legs, in the same way that water from a water tower runs downhill. Your bones and muscles also have to be strong to keep you upright against the pull of gravity. When you lie horizontally, the blood no longer pools in your legs, and your muscles and skeleton have no weight to bear. The effect is the same as weightlessness in space. The deterioration of the body during space travel also occurs in bed rest.
Releasing the Pressure
Let's examine this degeneration in detail. Essentially, our bodies are adapted to the force of gravity, particularly our bloodstreams. As upright animals, we tend, during the day's activities, to accumulate blood in the lower parts of the body. More importantly, the pressure from this pooled blood causes water to accumulate in the muscles and other tissues of the legs.
Every muscle cell is like a tiny canvas bag, and gravity causes water to fill these up. When the cells are full, the muscles in the legs are firm and offer support to the large deep veins in the legs. Without this support there would be nothing to stop the veins expanding more and more as blood pooled into the legs. If the veins were allowed to expand in this way, too much blood would accumulate in the legs and there would not be enough blood returned to the heart. This in turn would decrease the heart's ability to pump blood to the brain, resulting in fainting.
Water in the Legs
Usually, when you're upright and active, there are about five pounds of water in your legs. When you stay in bed, this water pours out of the muscle cells and enters your bloodstream. The body, in many remarkable ways, begins to adapt to this influx of water. As the water pours into circulation and increases the volume of blood, the upper chambers of the heart are stretched. Tiny nerve receptors are sensitive to this change and relay a signal to the brain that the blood's volume needs adjusting. Immediately, the brain relays the message to the small pituitary gland that rests underneath it and is directly connected to the brain.
One of the normal functions of the pituitary gland is to release a chemical that prevents the kidney from pouring too much water into our urine (antidiuretic hormone). When the signal is received from the brain that there is too much blood in circulation, the pituitary stops releasing this chemical; this leads to the kidney's releasing enough water from the bloodstream to lower the volume again. The process continues until all the body water necessary to adapt to a gravitational situation has been released. Usually a healthy adult will lose five pounds in 48 hours. Some can lose that much in 24 hours.
Once the water is lost, the body is no longer adapted to standing upright. The amount of blood in circulation usually decreases by more than a pint because of the water loss. The muscles in the legs, now soft, do not provide enough support for the deep veins, so that when you eventually stand up, excessive amounts of blood pools in the legs. Water pours out of the circulation into the water-thirsty muscle cells, decreasing even further the amount of blood available for pumping to the brain. Apart from trouble in the veins, the arteries change, too. Ordinarily, when you stand up, the arteries below the heart—in the legs—constrict. It is just like turning off the valves to a plumbing system. Pressure rises in the rest of the circulation, and is maintained at a sufficient level to pump blood uphill, against gravity, to the brain.
Getting Up to Faint
The opening and closing of the arteries is controlled by a nerve reflex which is kept active by our changing exposure to gravity as we get up or lie down. During prolonged bed rest, this nerve reflex mechanism is, of course, not stimulated, and so does not function as well as it should. When you finally do get out of bed, its response to the stimulation of gravity is sluggish. The result: too much blood pumped by the heart runs down relaxed arteries to the legs, and there is insufficient pressure to send enough blood to the brain.
The combined effect of these changes in muscles, veins, and arteries is to make you more likely to faint. Many quite healthy young men, after several days' bed rest, will faint if they have to stand still. The same thing happens to you when you go to bed with a minor illness. When you get up you feel faint from bed rest—not from the illness.
Most of the astronauts who have been on prolonged space flights have experienced similar problems when they first returned to earth. After you have been up and about a while, the tissues refill with water, causing the body weight to return to its usual level. The reflexes return to normal and you become readapted to the earth's gravity force.
Normally a certain number of red blood cells are destroyed each day from simple mechanical wear and tear. The bone marrow manufactures just enough new ones to maintain the right number of red blood cells. During inactivity, fewer cells are destroyed and the bone marrow activity slows down. The rich red marrow becomes pale and yellow. There is a gradual diminution of red blood cells. When activity is resumed, the old red blood cells are quickly destroyed and the bone marrow isn't ready to replace them. It may take as long as three weeks to readjust the proper balance between cells destroyed and manufactured. During this period an anemia develops, which in some instances is fairly severe. This is one reason why physical activity should be increased slowly.
Resting the Heart
Bed rest causes gradual changes in the heart. Slowly the heart gets smaller in size and the resting heart rate increases. This combination means that the heart pumps a smaller amount of blood with each beat and beats more often to circulate the same amount of blood. The heart, quite simply, begins to lose its previous level of efficiency.
Ordinarily, the excess products from released adrenalin are burned up by the increased metabolism caused by physical activity. During bed rest these chemicals accumulate in the heart muscle and brain, and in many ways they affect these organs like the build-up of excess carbon in an engine. They decrease the heart's ability to utilize oxygen economically, further decreasing the efficiency of the heart muscle. These chemicals also contribute to a gradual increase in the resting heart rate. Of course if the heart is already overworked this does not occur, and then rest is beneficial for the heart. You can, however, rest the heart as well, or better in many instances, by sitting up as opposed to lying down. If one remains inactive there is actually a little less work for the heart to do sitting upright than lying down.
A complete network of small arteries normally interconnects the branches of the large left and right coronary arteries to the heart muscle, and these are essential in delivering blood in large amounts to the heart muscle during exercise. During prolonged bed rest, these interconnections begin to close—significantly impairing the capacity to increase blood flow to the heart muscle when it is needed. One of the beneficial effects of proper exercise is to develop the circulation to the heart muscle. Bed rest and inactivity tend to have the opposite effect.
The combination of effects of bed rest on the circulation seriously impairs a person's ability to exercise. After prolonged bed rest the heart is not able to pump as much blood while exercising in the upright position. The smaller size of the heart after bed rest appears to be one limiting factor. The heart has to work much harder to enable the body to do the same amount of exercise. This is probably related to changes in the circulation within the skeletal muscles, and is evidence of loss of circulatory efficiency. It is another effect that has also been observed in astronauts after prolonged space flight.
Loss of Muscle Mass
The bony skeleton maintains its strength and calcium stores because of the constant stress of gravity on the upright body. Exercise in the gravity field tends to increase the density and strength of the bones. Bed rest negates the effects of gravity and the bones begin to get soft because they lose their calcium stores. Over a few days' time this isn't important in normal people, but as time goes on the loss of calcium can become significant. If you have a broken bone, the loss of calcium is more rapid. In sick people at bed rest for long periods of time, the calcium mobilized from the bones may clump together in the kidney and cause a kidney stone. The upright position, even if you are inactive, helps to prevent loss of bone calcium.
Your daily activity affects your amount of muscle mass. A weightlifter or a heavy laborer will have large strong muscles that feel firm to the touch. An inactive office worker will have soft, underdeveloped muscles. Even a muscular person will begin to lose his muscle mass at bed rest. First there is the pouring out of water, then with disuse the muscle tissue literally turns to fat. We know that fat, tender meat is produced by heavy feeding of inactive or penned animals or birds. Bed rest does the same thing to us.
When I first started studying the influence of bed rest on people I was startled to see that on a high-calorie diet most of the young men lost weight. This didn't make sense, because they shouldn't have been using many calories at bed rest. The answer was that their muscles were being converted to fat. Five pounds of muscle contains only as many calories as one pound of fat. Obviously for every five pounds of muscle converted to fat tissue the body weight would decrease four pounds—even if there had been no loss of stored calories. The difference in calories in muscle and fat tissue is explained by the fact that muscle contains much more water than fat tissue, and fat contains more calories than proteins. A pound of lean muscle is over 70 percent, water while a pound of fat tissue contains less than 20 percent water. The actual amount of protein in lean muscle is less than one-third of its weight while there is four-fifths of a pound of fat in a pound of fat tissue.
After several weeks of bed rest, the leg muscles are weak. Prolonged standing, barefoot, causes pain in the feet. The normal strength of the muscles in the feet is lost and allows strains on the bony joints.
Release the Breath
Another effect of lying down is increased difficulty in breathing. The diaphragm rises in the chest—decreasing the usual upright lung capacity. In healthy people at sea level this doesn't make much difference, but in individuals with respiratory problems or those exposed suddenly to altitude, it can be important.
In sum, if you are inactive—even if you are upright—gradually the body functions begin to deteriorate. There is a slow loss of body mass as muscle is converted to fat. The heart is affected, the bones, the bone marrow and the red blood-cells are affected. This is why the office worker with limited activity needs an exercise program. That fatigued feeling at the end of the day is caused by inactivity. Bed rest accelerates the loss of body function from inactivity.
Knowing what we now do about bed rest and its harmful effects, I think you should not go to bed for minor illnesses. You might be wise to stay at home but, if you need rest, you should get it sitting up and not lying down—except for the normal night's sleep. Bed rest for some sick people is an added hazard, not a help. Far from being a panacea, it can be part of the problem.