Stress gets a bad rap. Everywhere you look, stress seems to be getting the blame. Though as Richard Shweder wrote in the New York Times, “Imprecise and evasive language may be a disaster for science but it is a boon in everyday life. ‘I am stressed out’ is non-accusatory, apolitical and detached. It is a good way to keep the peace and, at the same time, a low-cost way to complain.” 
Selye said that, “Everybody knows what stress is, but no one really knows.”  Hans Selye is considered the father of modern stress research. He was one of the first scientists to conceptualise and measure this ethereal force.
As with some of the most important discoveries in the history of science, Selye came upon the discovery of what he termed the “alarm reaction” incidentally when he was injecting rats with impure ovarian extract, and noted that they became sick. He looked further at the physical changes in the rats and noted an unusual cluster of changes to their adrenal glands, thymus, spleen and gut . He was able to reproduce the same responses by exposing the rats to cold temperatures, surgical injury, spinal shock, excessive muscular exercise, or intoxications with sublethal doses of drugs such as adrenaline, morphine or formaldehyde . After years of research, he confirmed that ongoing exposure to the same physical conditions or drugs would follow the same three-stage process of initial physical changes, recovery and adaptation, then eventually exhaustion (and death). He called this model the “General Adaptation Syndrome.” 
The General Adaptation model was groundbreaking, and the sheer volume of work done by Selye brought his theories to the forefront of the scientific community. With time, the theory slowly descended from its place of adulation as other evidence came to light , but it has remained foundational, and Selye is still revered as the father of modern stress research.
The term stress “generally refers to experiences that cause feelings of anxiety and frustration because they push us beyond our ability to successfully cope.”  Scientifically, stress has been difficult to define. Different researchers often use different definitions of stress depending on what they’re studying or what field of psychology or science they belong to .
I wanted to look at stress from a different perspective. In the next series of posts, I want to look at the basic concepts of stress and its functions in nature. I will spend some time looking at different ways of conceptualising stress, and look at how they offer is life lessons on how to approach our stress. I’ll then have a look at what it is that helps us cope with stress.
A broad concept of stress
To gain a better understanding of stress, it’s useful to step away from the medical concept of stress, and think about what the term means in other fields.
When an engineer thinks about stress, it’s usually in relation to a physical force on a material object. My son is a huge Mythbusters fan. He was watching an episode the other day where the Mythbusters were testing the myth of Pykrete, a material that was nothing but wood shavings and ice. They were testing to see whether it was more durable than ice alone, whether it was bulletproof, and whether it could be used to build a boat!  In order to test out these crazy claims, they made some in their workshop and compared it with normal ice. How did they test it? By stressing it – placing weights on the end of the block of the ice/pykrete until it broke. (In the end, pykrete was ten times stronger than ice, was bulletproof, and they made a fully operational motor-boat from it!)
So the mechanical definition of stress is, “pressure or tension exerted on a material object.”  There are a few illustrations of mechanical stress, in our bodies and in everyday life, that are good metaphors for stress in our lives.
The Classical Stress/Productivity Curve
I confess I am NOT a musician. I’ve never learnt to read music or play an instrument. But I do know that when you first put a new string on the guitar, it’s unstretched – there is literally no force on it at all. If all you did was tied the two ends of the string to the tone peg and the tuning peg, the string would remain limp and lifeless. It wouldn’t be able to do anything useful. It certainly wouldn’t play a note.
When the tuning peg is twisted a few times, there is some tightness in the wire. The string is now under tension (i.e. stress). It is now able to play a note of some form, so it can do some work and fulfill some of the function of a guitar string. But the pitch isn’t good enough – the note is out of tune.
With a small adjustment, the string reaches its optimal tension and can play the correct note! This is the point where the string is fulfilling its designed purpose. Optimal stress equals optimal function.
With further tightening of the string, the perfect pitch is lost, but the string can still produce a sound of some form. With more tension, the string can still make a noise, but it sounds awful, and the fibres inside the cord are starting to tear. If the string were wound further and further, it would eventually break.
If this ratio of the tension of the string versus the usefulness of the string were to be plotted as a graph, it would look like an upside down “U”. This is the classic stress/productivity curve.
The Exponential Stress/Productivity Curve
The second metaphor that I think illustrates a different concept of the stress/productivity relationship is a car.
As well not being a musician, I am also NOT a mechanic! I know the important things like where the petrol goes, and how to drive them, but otherwise cars are very mysterious and powerful devices, their mystery is only exceeded by their power.
What I do know is that the engine is very much like the guitar string. As more petrol is fed into the engine, the engine gets more powerful. Soon, the engine finds its “power band”, a zone of maximum torque that can be achieved at moderate revolutions. As the engine is given more gas, the power output declines from the middle of the power band. If the engine was maxed out then the amount of functional power coming out is reduced.
This would plot as a similar graph to the U-curve of the stress/productivity curve. But cars not only have engines, but also a gearbox. The gears allow for multiplication of the work done (the productivity) for the same stress on the engine.
As a child, I didn’t dream of becoming an astronaut, but I was interested in space. The beauty of our night sky is as stunning as any forest, river or mountain. I would read of the astronauts in rockets and in space stations, floating around in zero gravity, swimming through the “air”. That sounded like a lot of fun.
But zero gravity isn’t particularly good for you. Some early astronauts had to be carried off their landing craft on stretchers because the effect of zero gravity would render these men weak and atrophied. They boarded the spacecraft at the peak of their physical strength and fitness, but after only a few weeks without gravity, their bodies resembled that of the elderly (although without the wrinkles) .
It’s a general principle of the human body that any tissue that isn’t needed shrinks in size – a process called atrophy. In zero gravity, the body doesn’t need as much muscle, so the muscles shrink. The body doesn’t need as much bone strength, so the bones weaken. There is no gravity to pull their blood away from their head, so the blood volume decreases. Because there is less muscle to pump blood to, and less blood to pump, the heart doesn’t work as hard, so the heart muscle atrophies. The net effect of zero gravity is to make you physically weak .
On the other hand, too much gravity is not great either. Animals can adapt to small amounts of hypergravity . But large amounts aren’t so good. During astronaut training, NASA subjects the rookie spacemen to rigorous tests including placing them in a large centrifuge and spinning it very fast. The result is an increase in the gravitational forces applied to their bodies. The increased gravity makes everything in the body heavier and their blood is pulled towards the legs and away from the brain, which leads to what is known as G-LOC (Gravity-induced Loss Of Consciousness). In other words, the heart can’t fight the increased force of gravity and the brain loses its blood supply, which makes you pass out. Josh McHugh did an entertaining piece on his experience with G-LOC and the centrifuge in Wired (2003) .
In this sense, gravity is to us physically like stress is to us mentally. Without gravity, our physical bodies turn to mush as we slowly weaken from the inside. Too much gravity, and our physical bodies are slowly squashed by the invisible weight of the extra G’s. Our bodies work best at 1G.
In the next post in this series, I’ll look at how these different models of stress apply to our everyday.
- Shweder, R.A., America’s Latest Export: A Stressed-Out World. The New York Times, New York, 26 January 1997 http://www.nytimes.com/1997/01/26/weekinreview/america-s-latest-export-a-stressed-out-world.html
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- Beyond Entertainment / Discovery Channel, The Alaska Special 2 (Season 7, Episode 2), Mythbusters: 2009 Discovery Channel, 44min. http://www.imdb.com/title/tt1427433/
- Oxford Dictionary of English – 3rd Edition, 2010, Oxford University Press: Oxford, UK.
- Gravity Hurts (So Good). NASA Science | Science News 2001 [cited July 2013]; Available from: http://science1.nasa.gov/science-news/science-at-nasa/2001/ast02aug_1/.
- van Loon, J.J., Hypergravity studies in the Netherlands. J Gravit Physiol, 2001. 8(1): P139-42 http://www.ncbi.nlm.nih.gov/pubmed/12650205
- McHugh, J., Surviving 7G. Wired, 2003. November(11),
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