My wife and I went to Natalie's RPM class this morning at CAC. It was a pretty chilly walk across the salt-and-pepper bridge but the first track got us all warmed up.
The class was quite challenging. A couple of the songs involved a pretty fast-paced climb where we had a lot of resistance applied (or "on the fly"); I was sweating profusely. I was thankful for some of the built-in breaks that RPM has, where we do a few shoulder rolls, etc., before continuing to punish our legs.
Other challenges for us in the class were a 75-second sprint (ouch) and a few hard seated climbs. All-in-all great positive instruction from Natalie, good song selection, and a hard workout.