No kidding. The emphasis on forced made it a little confusing. It seems extremely likely that the "forced" can be internal. When I'm at CrossFit, the criteria of the workout force me to exert much more strenuously than I'm comfortable with.
> In one study from 2008, rats forced to run wound up with significantly more new brain cells after eight weeks than those who ran when they chose, even though the latter animals ran faster.
ha, when I read that article all I had in my head was images of me doing death-by burpees and thinking "... I hope there are health benefits to that, because it really hurts..."
I think the idea is that what you want to do differs from what you are doing, or what you must do. When you run faster than you're comfortable with, the will to do that comes from yourself. External forced, not using your willpower.
