I took a few yoga classes. The first 2 wiped me out. I had to go sit in the car for 15 mins before I drove home. I guess its getting the stamina back up. I'm not a huge fan of yoga, but it was relaxing. Part of the problem I found was looking up and down at the instructor since I never took yoga before and didn't know what I was doing.

Try it...take a spot near the door...you can always quietly leave. (talk to the manager at the gym...give them your story about concussion, etc. and that you want to "try" it out ...they were so wonderful with me giving me a free pass etc.