Every human is different, but yes I believe that's too much. If he had said, "I exercise 5 days a week, take 1 week off every 3 months and 2 consecutive weeks off per year." Then that is different. But he said he runs a 5k EVERY SINGLE DAY, and that is far too much abuse for a human body. The most insidious symptom of overtraining syndrome is a compulsive need to exercise.
If this individual is overtrained, his body will find a way to stop him. He will become ill from immune suppression or injured from the constant stress that never fully heals, or too depressed to exercise at all.
Body builders have a saying something like, "Muscles are made in the bedroom and the kitchen."
Prior to doing this, did you walk 10K every day? Curious about the diff between 10K run vs 10K walk. Personally, weightlifting 3x a week and roughly 10K walking every day does the same thing as running did.
I would love to do this but 10k/day is a lot. I tried it for one week and I was extremely exhausted. My productivity also dropped as I am very tired. What time of the day do you run?
Not the OP but that is not really how you start running 10K/day. You gradually build up endurance starting from a mile a day or so, till your lungs can deal with that. I run 5 miles on the days I don't weight lift. It is not exhausting or something. I do this in the morning and then go do my work stuff.
I'm not a beginner in running. Been running for more than two years but I find it hard to run 10k/day unless I don't have a job and don't go to work. I do the same I run on MWF and lift TThSat and that routine is ok for me. But running everyday is different.
The productivity gains are in the 2-3x range.