Taking a break from running due to a bum knee. Hope to

go back to it soon.  Thinking is good.  Playing music is good.  Just don't sing/hum to yourself while running.  There was a time when I tried to learn to breathe right.  I started singing/humming to myself while running to keep things in rhythm.  I don't know if you've ever followed "Seinfeld".  There is this episode wherein a character called George keeps humming "Master of the House" (from Les Misérables) incessantly as he has apparently developed an earworm.  Well, I ended up like poor George and it took me more than a year to shake it.  :)