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  • Writer's picturehidet77

Fatigue


Fatigue.

A natural phenomenon that we all have as a human beings.

And operations have to deal with this phenomenon systematically.


Some people believe machines are better since they don’t have fatigue. Humans have fatigue, and that should become process improvements. Unfortunately, most systems ignore it.


1️⃣ We don’t get fatigued “Mathematically.”

2️⃣ Mental fatigue

3️⃣ Muda (Waste) is Muri (Overburden).


1️⃣ We don’t get fatigued “Mathematically.”


One of the common approaches to fatigue is to calculate some fatigue ratio. The typical ratio would be “80%.”



But this thinking is strange in many ways.

The blue line represents what such a calculation will look like. From the beginning of work, an individual is performing 80% level. But this is different from how we humans get tired. We get tired in a different way.


The green line represents better how those mathematicians think about fatigue. We gradually get tired. 80% is the average of the shift.

I have never seen such a performance. Somebody who performs +20% at the beginning and at the end slows down -20%. If such a process did exist, then such a process would be horrible. The process should be different from the challenging Olympics game, where athletes are challenging the limits of humans. Operations are daily activities. How can we send our employees back to life after driving them tired to that level? 80% or 90%, such numbers don’t represent an accurate picture.


Some will argue that it is not such a linear line. There are more ups and downs since there are breaks. I always say that we are playing too many computer games. In games, there’s a character that gets tired or damaged. Then you use an item or spell, and the character recovers. I know some products in real life create such perceptions, too. “Energy” whatever or this feeling after drinking caffeine. Expecting such a product to function like a computer game is a joke. It is very misleading to think of fatigue mathematically.


2️⃣ Mental fatigue


One big reason we can’t use mathematics is that we get tired mentally.


One typical case is the unclearness of the work. It is unclear what to do, yet you are supposed to deliver some results. The other day, I was in a horrible warehouse. As soon as I entered, we started doing 5S. But at the same time, I was helping the warehouse guys to search for the parts. There are labels everywhere, but that is not accurate label. Some parts not used for five years are in the most convenient locations. Some pick list was a puzzle. It showed a number, but you have to pick something else. That few hours drained me. The supervisor joked that I was a serious candidate to work there since they have a high turnover. Of course, nobody wants to work in chaos. Slight confusion at work drives humans tired. This is one big reason we must have standards and standardized work.


Another type of mental fatigue that I frequently see in today's operations, especially in the service area, is the indefinite break. I often ran into employees talking to each other about whether they took a break or not. (And typically ignoring customers in front.) But how stressful they must be working without knowing when they can have one. Another example, I met an operator in the break room less than one hour before the end of the shift. And before that break, he worked more than four hours straight. What was this break for? Are they providing breaks for fatigue or to mitigate legal risks? Breaks are supposed to reduce fatigue, but in some cases, it is increasing it.


Of course, the sources of mental fatigue are plenty, and I do not intend to cover all. But they are plenty of sources that simple standards can eliminate.


3️⃣ Muda is Muri.


Muri (Overburden) is another source of fatigue. [I have different use of “Muri.”]

And what is the judgment of the overburden? Typically, local government has some policy. In the USA, 50 pounds is the limit. So anything below 50 pounds is not an overburden?

A simple rule that we should have is that the work must be tried by the manager & the process designer (engineer). If it is difficult for them, it is difficult for the worker. Don’t design something that a manager or the engineer feels uncomfortable with.


But the more significant source of fatigue is Muda (waste). An extra motion will make people tired. Fixing defects and cleaning scraps is wasted energy. Waiting makes people tired (Do you like waiting in lines?). Piling up inventories, transporting to distant locations, and doing unnecessary processes will drive people to exhaustion. Nothing will make people more tired is the over-production. Most operators know they are pushed to produce more daily, but whatever they produce is in the warehouse. They feel why I was rushed yesterday and pushed today, and the product sits in the warehouse. It is the feeling of any employee. You submit work by a “deadline,” but that work sits somewhere in the system. Now, the employee has to make follow-up emails and calls, dealing with he said, she said. The employee is thinking, what was my day for?


Kaizen is a great way to reduce fatigue. Start with the complaint, since people typically complain about what makes them tired. A better process will make the process less tiring. Improved processes will generate positive energy mentally.



Fatigue is a normal thing for us humans. It is not math. The best approach is standards and Kaizen. Fatigue is an advantage of humans because it highlights what we need to improve in the system. Instead of looking the fatigue as a “weakness,” converting it into a “strength” is what we need to do systematically.

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