First published in The Huffington Post 6th March 2017. After the First World War, much work was done to find a way to measure fatigue but it was deemed such a subjective concept as to be impossible to develop any meaningful way of objectively measuring it. It was not possible to fathom out the complex interaction between emotional, physical and mental aspects of fatigue in a way that could be reliably and accurately counted. And yet, we all know the feeling of being fatigued and how tired we are.
Roll forward a few decades and Dr Gunnar Borg invented a measurement scale that when exercising, would allow someone to express their level of exertion on a scale between six and 20. This score equated reasonably accurately with their actual heart rate (multiply the score on the scale by 10). Subsequent research has shown a quite remarkable link between the subjective sense of where on the Borg scale a person feels and the specific changes that take place in the body in response to exercise. For example, when people report being at or around 17 on the Borg Scale they have also reached the tipping point at which the blood concentration of lactate, a by-product of exercise, starts to rise exponentially. It’s also the point at which breathing whilst exercising becomes more laboured – a point known as the ventilatory threshold. Sports laboratories the world over use the Borg scale as a very convenient indicator in support of the other tests that they do. The Borg scale is a simple, subjective, reliable and accurate measure of exertion.
Today, the evidence is beginning to emerge that the use of subjective measures like the Borg scale can be applied to other complex processes such as mental fatigue. Research into physical exercise has demonstrated that the thing that stops us exercising more is not so much physical fatigue as mental fatigue. It’s our perception of effort and the value of that effort that governs our ability to perform and not so much the physical fatigue experienced by our muscles. As with fatigue, it’s complex. Physical fatigue fuels mental fatigue and mental fatigue reduces our capacity for physical effort. If we can measure simply and subjectively the level of fatigue an athlete is experiencing, then we can better set the right intensity and volume of training. It appears that something like the Borg scale works well for assessing an athlete’s capacity for work.
Qualitative and quantitative evidence is sometimes used as a weapon to force decisions through when not everyone involved is convinced. In the face of charts, spreadsheets and PowerPoint decks, gut feel seems like a poor response, and yet what we are learning from research into exertion and fatigue, is that it is one of the most useful tools in our armoury of tests. So let’s hear it for gut feel. My sense is we should take it far more seriously than we do.