No kidding! Yep, a tandem works your legs harder than a single, especially climbing. We rode RAMROD this year on our tandem. Out of 800 riders, I think there were 5 tandems and a lot of folks around here have tandems, too.

I think the difference is that the much greater weight of the tandem means that it doesn't "get out of the way" of your pedal stroke like a single does. A tandem puts a constant strain on your legs. But don't ease off! Ride that tandem and put away your singles. After about 6 months have a go on a single again. You will be amazed, along with all the folks in your mirror.

Stoker and I keep things "fair" by using HRMs. She has my HR on her Garmin and also her HR on another monitor. She matches her HR to mine since we both have about the same LT. If LTs vary as is more usually the case, the stoker would compensate appropriately. If I'm more tired that she, she'll run her HR a little above mine, and vice versa.