I'm in the market for a tri bike - up until now I've been riding a road bike, occasionally with clip-on aero bars. Lately I've been doing a lot of climbing and haven't raced in a few months, so the aero bars have been off for a while. I got fitted up for the tri bikes before I took them out for test rides, and then put in probably about 15-20 miles of total test riding time (on 5 different bikes).

I noticed that my hip flexors got tired/sore very quickly, and the next day, my quads are more fried than usual. I know that the steeper geometry on a tri bike (the seat angles on the bikes I rode varied from 76 to 78 degrees) causes different muscles to be recruited, but I've never seen an in-depth discussion of WHICH muscles are used more - so I'm wondering if this increased use of the hip flexors and quads is to be expected. I'm expecting a considerable adjustment period to the more aggressive aero position, but I'm curious as to what other people's experiences in making this transition have been.

Thanks for any info/feedback.

Scott