How much elevation is included in that 100? One of the guys in our club who does triathlons is doing longish rides, keeping his heart rate low, to work on base strength. I've been working on hills, and trying to keep up with the fast guys on one ride a week this winter in an effort to build my base. So far, my program seems to be working better, as my avg. heart rate was quite a bit lower than the tri-guy's on a ride last weekend.