sides of thighs ache

[Beckyridesamule]

I have been rowing in a tandem wherry for a spell, but recently bought a Concept 2 for the winter months. I am finding that the sides of my thighs start aching after just a short time on the erg. They don't ache in the wherry. What am I doing wrong that causes this?

[JRBJR]

I was wondering if perhaps your rowing position, the location of your legs and feet in particular, on the tandem wherry and Concept2 erg were so different as to cause you to strain underused leg muscles on the erg. But a Google image of the boat suggests that's not the case. If the pain persists, I'd suggest you consult an expert who can advise you, perhaps a sports physician.