I’m a physical therapist and I’d say the big reason is when you get tired doing an exercise the first thing to break down is form. People who work out regularly will stop at this point (unless they do CrossFit) but at work you have to keep going. That plus a lack of knowledge about form and injury leads to people doing a lot of poor movement patterns because it is less strenuous, like lifting with the back instead of the legs. Over time this injures knees, spine, shoulders commonly.
The thing I hate the most about it is it’s pretty predictable. If you make someone workout past what they are physically able to do they will find a way and it will hurt their body. It’s not fair.
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