I've been mountain biking for about a year and "thought" I was in pretty good shape but 3 weeks ago I got my first road bike. Since then my ride lenghs have increased almost 4 times since I find the road to be much more fun. I've also made amazing gains in going up hills. Hills that have kicked my ass for a year are becoming easy and my legs have already gotten bigger, because I keep pushing myself.
My problem is that at work I walk around a lot and do many steps. The steps have become a problem since when I go up them my legs will start burning and my heart rate will sky rocket. I feel like my body is gearing up for a massive hill. People have said to me that I should get in shape because my breathing will increase and it appears to others that I'm straining to make the stairs. Its not like I'm sprinting up the stairs or doing two at a time for 3 floors, but I'm getting a little concerned because today my legs "gave out" and I actually had to grab the railling to stop from falling.
Is this an issue of over-training or should I just take like 3 days off from riding and lay on my sofa when I get home?