Originally Posted by Wadester
I've read a few discussions about them. What I took away was that you've only got so much "whoopass". Having more ways to apply that to driving yourself forward does not give you more power, just lets you spread the load over more body parts - either all together or at different times (like after your legs need a rest).
The drawback is the additional weight of the 2nd drivetrain.
Here's some good reading:
It makes little sense from an aerobic perspective; the designs clearly don't consider the disparate cross sectional areas of each muscle group, so you very quickly experience the anaerobic shift in the upper-body portion, even if you're just "mailing it in." You could design some gearing to accomodate the difference in power, which strikes me as an awkwardly out-of-synch experience.
Want to feel the power of your whole body contributing to the power stroke? Get out of your seat and start hammering. Your whole body becomes a linkage, anchored at the bars. But I guess that's not an option when you're bent.