I've been riding 6 days a week for 5 months now, anywhere from 10 - 20 miles per day, putting my ALL into it, or so I thought. I was riding a 7 speed commuter bike and wanted to see if I was going to keep this up before spending the $$ on a better bike. Well, I'm addicted and after 3 weeks of serious shopping and test riding I found the perfect bike for me - fits like a comfortable shoe, and rides like a dream. Trek 7.6 FX WSD. My first ride was day before yesterday. I did my usual route and must have said OMG! about 187 times as I glided through my 20 miles. When I got home I was floored to see I had cut 20 minutes!!! off my time, but boy was I beat. I don't get it!! The same thing happened yesterday and today I'm just resting because I'm exhausted! I realize I am in a more bent-over position, and I can actually feel muscles being used that weren't being used on the commuter bike - is that it?? I am pretty sore today. I'm drinking and eating and doing all those other things you're supposed to do. Here I thought I was in pretty good shape after 5 months of riding - but obviously not. Should I take it easy on riding for a few weeks? Like only go 10 miles or so?