30 Minutes Running and 30 Minutes Spinning

I did 1:00/1:00 intervals this morning after a short warm-up.My left knee started to twinge after about 25 minutes, so I walked the last 5 minutes. I had planned to ride my bike in the early evening, but it rained. Instead, I set it up on the stationary platform that Bob loaned me and spun for 30 minutes. It worked really well, but it reminded me of being on a treadmill - you get your time in, but you don't get to go anywhere. I was in my hot garage. Even though the overhead door was open and a fan was blowing, it was still pretty hot. I would have preferred to have been outside.
We have an early seminar tomorrow, but I'm going to try to get up early and go for a swim before.