It's cold outside, and dark more than light. So, I've taken to intervals in the
garage. Thankfully there's a TV out there, or I couldn't even last the 30 minutes I've been spending on each session. Last week, it was a simple set of cadence intervals. Warm up, spin fast-ish for 4 minutes, rest 2, spin 3, rest 2 etc. The picture below shows the data from one of the sessions. The green line is the cadence; it's a steady block down, up, down, etc. The red line is heart rate (HR). The HR climbs through this short simple session. I'm taking that as an indication of the potential for a training effect. I did this 3 days in a row; the image is from the 3rd of these sessions. Then I took a couple of days off.
I'll try another couple of weeks with these intervals in the garage. Hopefully the weather improves enough that in mid-to-late Feb I'll get to move most of the riding outside.