From what I know about muscles and experience levels in bodybuilding there's "stages" for muscles according to "what are they able to handle". That's why we are taught to go "nice and slowly" by scooby and thats why I never seen a pro bodybuilder to go like that

Because probably, in such an experienced level of muscle, it is not that dangerous for them.
Now, from this knowledge, an interesting questions rises up for me.
When you go cardio, bike or running, even in fast walk muscles are making pretty fast movement. If your leg muscles are in "beginner level stage" isn't it unhealthy for your muscle developement?
Thanks for answers
