Fatigue: Is It a Stress or a Strain? Is fatigue an injury to the
human body from which we need time to recover? Or is fatigue just being
tired or over tired, for which a good night’s sleep is the common
remedy?
That is the question: is fatigue just a stress on the body and mind and as such something from which the body and mind can bounce back without any damage? Or is fatigue rather something more insidious than just a stress? Is it possible that fatigue is actually a strain, that is to say, an injury, some kind of damage to the body and mind? If fatigue is an injury to the body and mind, and overstress resulting in a strain, does the the body and mind need time to heal back to health from this injury?
Does repeated stress lead to more damaging strain? Can the road to recovery from the strain of fatigue to the body and mind be a lot longer than just one good night’s sleep?
I am a professional international pilot of 40 plus years, twenty in the US Navy, much of it on carriers with extended hours, much of it at night and twenty at a global package delivery airline, much of it in international operations and much of it at night. I have a degree in liberal arts and a degree in metallurgical engineering. I have no degree in sleep-ology, so any sheep skin focused stickler can stop reading right here.
But I am a human being who has spent many nights and days working multiple shift hours far in excess of any reasonable eight or ten hour schedule, over tired, falling asleep at the switch as the saying goes from fatigue, but trying to do a good job, a necessary job and trying to have a life outside of work at the same time. The one thing that I have noticed is that recovery from fatigue seems to take much more time than just one good night’s sleep. So I began to wonder why? Was I injured and needing to heal? But where was the injury, how can I feel it and how can I measure it? How much time did I need for full physiological recovery of my body and my mind? Was I required to sacrifice the health of my body and my mind for some jobs? If so, how am I being separately compensated for both the work I do and the sacrificing of the health of my body and my mind?
Well again, I didn’t study physiology in college, but I did receive a reasonably good education in flight physiology during these past 40 years and I have read most of what the fatigue and sleep experts have written in industry literature. It is all good, many studies, great work by some fine people. And I didn't study labor relations and compensation, but I did recognize that there are two issues to working at night and working extended hours repeatedly, the issue of compensation for the work and compensation for the hours past any reasonable shift.
But even then I often come away with more questions fatigue than answers. What is the pineal gland anyway and how does it work? Does the brain need oxygen and sugar to function? Why does worry have the same affect as caffeine? Why is a hot shower so refreshing when tired? Why do kids fall asleep when tired where ever they sit down? Why do older folks struggle often with sleep? Why do I feel so tired on weekend layovers that I just want to relax and do nothing stressful, just recover and hope for restful sleep? Why does fatigue knock your brain out like a light switch turning off, even when you are not lying down in bed? How does it know to do that? What else do we not know about fatigue?
So, in my curiosity I harkened back to my university days studying metallurgy. I remembered that we studied the physical relationship between stress and strain on a metal sample and on samples of wood, plastic, ceramics and other material. Stress is the force that is applied to the metal sample and strain is the amount of deformation that occurred to the sample piece as a result of the stress.
What we found was that for the most part, metals deform elastically under lower levels of stress and essentially return to their original shape, size and strength. This means that the stress is borne by the material and it springs back into its original being.
In physiology terms, we might say that one all nighter isn’t so bad; just get a good night’s sleep and you will bounce back, good as new and be ready to go just fine. Probably all true, especially so for lab studies.
Now back to the metal samples. As we continue to add stress to the metal samples, somewhere down the line we get strain that is no longer elastic. The sample now begins to deform. It is still strong and has some of its original strength, but it has become bent, stretched and weakened. The stress that was put on the sample past the elastic strain point damaged the sample. It is deformed plastically, that is, it will no longer spring back into it’s original size, shape and strength. Moreover, if the stress is continually applied, not only does the strain become a deformation in size, shape and strength, the sample will eventually break, fail and just come apart, often with a very loud bang.
Now, back to the human physiology story. Again I am not an expert, but I wondered if the human body and mind did not react in a similar manner, that is to say, that the body and mind can take some stress, some sleeplessness, and bounce back elastically with just a good night’s sleep.
But what happens to the human body and mind when the stress of sleeplessness is applied continuously, and applied over the ability to take this stress undamaged? Can the stress eventually cause a strain, that is, damage to the body and mind, damage that one good night’s sleep is insufficient time in which to recover? Can we over stress the body and mind with fatigue? Can fatigue be damage that affects the body and mind such that it is injured and needs time to recover from the injury?
I don’t know the answers to all of these questions. But I believe that these questions need to be asked. Is fatigue more of a strain at some point that just a stress? Can we do injury to our bodies and minds by stressing them with fatigue to the point that they are damaged in some manner and no longer function well? Can this damage be such that one good night’s sleep is insufficient in which to recover? Have we broken something that needs mending? Have we injured something in ourselves which needs recovery?
Is fatigue more of a strain than a stress?
That is the question: is fatigue just a stress on the body and mind and as such something from which the body and mind can bounce back without any damage? Or is fatigue rather something more insidious than just a stress? Is it possible that fatigue is actually a strain, that is to say, an injury, some kind of damage to the body and mind? If fatigue is an injury to the body and mind, and overstress resulting in a strain, does the the body and mind need time to heal back to health from this injury?
Does repeated stress lead to more damaging strain? Can the road to recovery from the strain of fatigue to the body and mind be a lot longer than just one good night’s sleep?
I am a professional international pilot of 40 plus years, twenty in the US Navy, much of it on carriers with extended hours, much of it at night and twenty at a global package delivery airline, much of it in international operations and much of it at night. I have a degree in liberal arts and a degree in metallurgical engineering. I have no degree in sleep-ology, so any sheep skin focused stickler can stop reading right here.
But I am a human being who has spent many nights and days working multiple shift hours far in excess of any reasonable eight or ten hour schedule, over tired, falling asleep at the switch as the saying goes from fatigue, but trying to do a good job, a necessary job and trying to have a life outside of work at the same time. The one thing that I have noticed is that recovery from fatigue seems to take much more time than just one good night’s sleep. So I began to wonder why? Was I injured and needing to heal? But where was the injury, how can I feel it and how can I measure it? How much time did I need for full physiological recovery of my body and my mind? Was I required to sacrifice the health of my body and my mind for some jobs? If so, how am I being separately compensated for both the work I do and the sacrificing of the health of my body and my mind?
Well again, I didn’t study physiology in college, but I did receive a reasonably good education in flight physiology during these past 40 years and I have read most of what the fatigue and sleep experts have written in industry literature. It is all good, many studies, great work by some fine people. And I didn't study labor relations and compensation, but I did recognize that there are two issues to working at night and working extended hours repeatedly, the issue of compensation for the work and compensation for the hours past any reasonable shift.
But even then I often come away with more questions fatigue than answers. What is the pineal gland anyway and how does it work? Does the brain need oxygen and sugar to function? Why does worry have the same affect as caffeine? Why is a hot shower so refreshing when tired? Why do kids fall asleep when tired where ever they sit down? Why do older folks struggle often with sleep? Why do I feel so tired on weekend layovers that I just want to relax and do nothing stressful, just recover and hope for restful sleep? Why does fatigue knock your brain out like a light switch turning off, even when you are not lying down in bed? How does it know to do that? What else do we not know about fatigue?
So, in my curiosity I harkened back to my university days studying metallurgy. I remembered that we studied the physical relationship between stress and strain on a metal sample and on samples of wood, plastic, ceramics and other material. Stress is the force that is applied to the metal sample and strain is the amount of deformation that occurred to the sample piece as a result of the stress.
What we found was that for the most part, metals deform elastically under lower levels of stress and essentially return to their original shape, size and strength. This means that the stress is borne by the material and it springs back into its original being.
In physiology terms, we might say that one all nighter isn’t so bad; just get a good night’s sleep and you will bounce back, good as new and be ready to go just fine. Probably all true, especially so for lab studies.
Now back to the metal samples. As we continue to add stress to the metal samples, somewhere down the line we get strain that is no longer elastic. The sample now begins to deform. It is still strong and has some of its original strength, but it has become bent, stretched and weakened. The stress that was put on the sample past the elastic strain point damaged the sample. It is deformed plastically, that is, it will no longer spring back into it’s original size, shape and strength. Moreover, if the stress is continually applied, not only does the strain become a deformation in size, shape and strength, the sample will eventually break, fail and just come apart, often with a very loud bang.
Now, back to the human physiology story. Again I am not an expert, but I wondered if the human body and mind did not react in a similar manner, that is to say, that the body and mind can take some stress, some sleeplessness, and bounce back elastically with just a good night’s sleep.
But what happens to the human body and mind when the stress of sleeplessness is applied continuously, and applied over the ability to take this stress undamaged? Can the stress eventually cause a strain, that is, damage to the body and mind, damage that one good night’s sleep is insufficient time in which to recover? Can we over stress the body and mind with fatigue? Can fatigue be damage that affects the body and mind such that it is injured and needs time to recover from the injury?
I don’t know the answers to all of these questions. But I believe that these questions need to be asked. Is fatigue more of a strain at some point that just a stress? Can we do injury to our bodies and minds by stressing them with fatigue to the point that they are damaged in some manner and no longer function well? Can this damage be such that one good night’s sleep is insufficient in which to recover? Have we broken something that needs mending? Have we injured something in ourselves which needs recovery?
Is fatigue more of a strain than a stress?
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