Different muscle groups stressed...trainer vs road

I notice when I get DOMS after a road ride it is primarily in my vastus medialis. When I’m sore from riding on the trainer it is primarily my quadriceps. For the most part, I don’t care…but maybe I should?

Anybody have a similar experience or thoughts about why such a difference might exist?

In short, what you are experiencing is most likely related to differences in inertial that manifest in the muscular loading during the pedal stroke.

Good article about climbing vs flat riding:

For trainer, the ability to use different gearing in ERG mode may allow for more specific targeting of muscular loading, to more accurately match your needs for outside riding.

This whole topic has some great discussion in this thread.