I began running regularly last winter during my lunch break. When all goes well, I run six miles a day-M, W, F, and bring my road bike in on Tue & Thurs to do a an hour of steep hill climbs. During both runs & rides I like to incoprporate alot of interval training.
If you are looking to be a Norba supertar this is probably not the smartest thing to do, but if you are a regular jo-blow spoort racer it will probably help you. IMO, most people worry too much much about VO2 max, heart rate, lactic acid, and all the other hard core mumb-jumbo. I say get out there and bust your ass, become familiar with Suffering, shake his hand, become friends
...soon you will become a sick freak and no one will want to ride with you.