Is this odd?

[Nightsky565]

I just started cycling about 3 weeks ago, before that I was really inactive. I find that I can't make my legs burn out.... I am riding a pretty heavy MTB with nobby tires at about 23kmph for 70-90km and my legs just don't hurt. My chest hurts before my legs hurt.... Although when I get home its hard to walk up the stairs... I am used to lifting weights where you feel the burn instantly, am I not working hard enough? I want to get stronger and maybe race in a few years.

[KingTermite]

I've noticed same thing as you.....

I've been riding for over a year, but just started getting "the bug" in the last few months and riding 3 or 4 times a week. I never really feel problems with my legs (seldom anyway) while riding, but lately I feel them "burn" when I try to climb the stairs at work.