Rookie Mistake or Minor Blip?

I think I made a rookie triathlon blunder. I'm still not sure. I’m a wimp when it comes to my trainer. Knowing that I only had one ride before the D.C. Tri this Sunday, I decided to opt out of switching out my tire to use on the trainer and instead sat in on a spin class. This was a little awkward because I wasn’t following the spin instructors routine, but it was nice—good music, inside, spared the hassle of switching out my rear tire.

But today, my bike laziness has come back to bite me: my hamstring feels wonky and my legs feels a little worse for the wear. I don’t know if the spin bike uses different muscles, or whether the (temporary) new position affected them, but it just feels “off.” Did I just commit a newbie sin? Should I actually avoid spin bikes like the plague and just suck it up and break the trainer out of storage? Well, we'll see how the race goes this weekend!