Just a caution here though Magrat,

You might want to check in with your doc too, just to cover your bases. -- Unless of course you have always been in shape, and it's just "biking" that you are new to, and not exercise as a whole. Never a bad idea to let your doc know what you are up to. He/she can make sure your BP, Hemoglobin, blood sugar etc are all up to snuff, and ready for intensive exercise.

On the other hand, my brother used to be a doc in the Navy and said his Marines told him that...

"If yer not pukin', yer not tryin'"

Somehow that doesn't seem too appealing to me - hee hee!