Night_Manager
My shift-workers are not understanding the concept of fatigue. They are confusing it with other human states. What states have you seen it confused with? Does anyone have a term that clarifies the concept of fatigue as we see it?
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In the clinical world, the term fatigue is usually used to describe a state of lethargy that is normally linked to psychological conditions more so than to sleep problems. Understanding the source of the symptom of fatigue is important for clinicians because they try to recommend treatments to address the source. If the source is a psychological condition like depression or anxiety, the recommended treatment is aimed at these conditions and not at sleep. As Fatigue Managers, we are more concerned with the symptom of fatigue when it is linked to sleep factors than when it is “lethargic fatigue”.
There are two additional uses of the term fatigue that get confused with the sleepiness use of it. If we exert ourselves physically or mentally in an intense fashion for a short period of time or less intensely, but for a long time, we will often say we are fatigued. For example, after working out intensely and physically at the gym for 30 minutes without a break or after going through an emergency situation without a break that required a great amount of mental effort in a short period of time, we will often describe how we feel as “fatigued”. We do not say we are sleepy. Or, if we spend a whole day walking around town sightseeing without taking any breaks we will often say “I am fatigued.” Likewise, after spending many hours reading a boring textbook without any breaks, we can feel fatigued. In these situations, if we have slept well and long enough before we exert ourselves physically or mentally, and we have not been awake for a long period of time, we do not fall asleep more quickly than people who have not experienced these situations. This means that when we say we are “fatigued” in these cases, we must be experiencing something different from sleepiness. I call these types of fatigue, “physical” and “mental” fatigue.
A quick side note is in order here. Some of the regulations do mix up the types of fatigue. For example, here in the USA the FAA messed up the definition of fatigue. They stated that fatigue can result from increased physical activity. Check out their definition of fatigue here: https://www.ecfr.gov/current/title-14/chapter-I/subchapter-G/part-117/section-117.3#
While this is true for physical fatigue, it is not true for fatigue if we are using the term as a synonym for sleepiness. There is no research that indicates, in the absence of sleep related factors, that physical activity leads to sleepiness.
There are many more types of fatigue and uses of the term; but, thankfully they do not get mixed up too often in the safety realm. You have probably taken note when you hear people talking about things like compassion fatigue, voter fatigue, COVID-19 fatigue, chronic fatigue syndrome and even material fatigue (e.g., the fatiguing of metal over repeated strain). These are all very different from the fatigue we are talking about.
I am going to introduce a term that will help us keep all these uses of the word fatigue straight. To link the term to the conditions that cause sleepiness, like inadequate sleep quantity and quality, circadian rhythm effects and prolonged wakefulness, I use the term sleep-related fatigue. I think it is a perfect term for distinguishing between the type of fatigue we are talking about and all the other types. The Transportation Safety Board of Canada thinks so too. They renamed their fatigue investigation manual to the Guide to Investigating Sleep-Related Fatigue. You can get this guide here: https://fatiguemanagersnetwork.org/wp-content/uploads/Canada_Transportation-Safety-Board_Investigating-Fatigue-Guide-Two-2014-2015-EN.pdf in English and here in French: https://fatiguemanagersnetwork.org/wp-content/uploads/Canada_Transportation-Safety-Board_Investigating-Fatigue-Guide-Two-2014-2015-FR.pdf
This term is slowly making its way into fatigue regulations and guidance material published by regulators and governing organizations, and I credit the TSB for it.
In all of our documentation and all our training we state something like: “From this point forward, let us keep things clear by either using the term sleep-related fatigue or by agreeing that when we are talking about fatigue, we are referring to this type of fatigue unless we specify otherwise.”