I agree with you. I'm an avid mountain biker and ride every chance I get for at least an hour. When I'm going at race pace, or near race pace, my mind does 1 of 2 things.
1. My mind will be 100% focused at the task at hand. (Pedal faster, smoother, avoid that tree, jump, get off the saddle, drink water, etc). My mind drowns everything else out and is just focused on the trail. I find this therapeutic because I can forget about everything else going on in my life. It's an escape from reality for an hour or two. When I'm done, it mind tends to stay this way and I'm usually productive afterwards.
2. I won't be 100% focused on the trail, and I'll be planning other things. I'll be thinking about a solution to a problem I've encountered at work (I'm a software engineer), or I'll be planning my next race, or planning something else. I'll also think about tasks I need to complete at work or errands I need to run this week, etc. It's weird because my mind will retain this all this information for several hours, and I may or may not have to make notes after I'm done.
It's strange because they seem to be the opposite of each other, but I find it refreshing no matter what happens. The mind is a strange like that I guess.