Not trying to patronize you at all, and I apologize if it came off that way. I'd say that most people in the tech/hacker community aren't too well acquainted with consistent, dedicated exercise. It wouldn't be unreasonable for someone to have the belief that after 6 months of 7 minute circuits, their body should be well adapted to intense workouts. Since I don't know who you are or where you stand on the experience spectrum, I took an educated guess, and apparently was wrong.