Originally Posted by
bikerjp
As for not staying in zone 2 on a training ride I don't think anything happens. In fact, I've read that it's good at times to do 10 min hard efforts every hour of a zone 2 ride. It's pretty hard to hold a certain HR for a long period of time. I go more for average.
I would agree going hard every know and then during a Z2 ride can be a good thing. I also think that a 2-4 hour ride in only Z2 is great workout. Read Chappel's "Base Building for Cyclists" and you'll understand why. Has a lot to do with how your body uses fat for fuel and as a result gets really effecient, over time, using fat a the major fuel source. That effeciency then can be translated into faster cycling speed at your given HR.
I don't use power, so I won't write about an increase in average speed only to get raked over the coals for it. All I can say is I have done this "base building" and seen some nice gains.