Originally Posted by nitroRoo

Welcome to cycling! As someone who lost 50+ lbs through crossfit and running, then turned to cycling, I get where you're coming from. While your p90x and running background will definitely help you, cycling uses some different muscle groups and is taxing in a different way - especially when climbing. 10 miles on your first ride is a good start! Prepare for your butt to feel a little sore/bruised and for your legs to feel sore (especially going up stairs!). But, keep it up and those hills will get easier and easier. If you can get in a ride at least 2-3 times a week, you'll be surprised at how much better you feel in a month or two. You'll be able to stay in higher and higher gears as you climb, and your legs won't start burning nearly as fast. Suffer through the first bit, because it definitely gets better!

The great thing about being faster and stronger is that you'll get up those hills quicker. When you are new it's extra bad because not only do your legs and heart feel like they might explode, you are stuck pedaling in a low gear, going slow, which means you are suffering for even longer. But that's what it takes! Good work - keep it up!