Thanks everybody for the replies. Very useful indeed (except one, you know who you are.)
I'd like to go off a tangent on something chasm54 wrote:
Originally Posted by
chasm54
Therefore, the answer to the OPs question is that he would be better off doing the bulk of his training below his threshold, and building a big aerobic base by so doing; and supplementing that with shorter, much more intense efforts to bump up his threshold and VO2 max.
I have measured my resting HR, but not my max, so I just went with 220 - age = 188. That gives me a fat burning range of 135-148 bpm (and I've been there when riding with my sister: I barely feel anything), and an aerobic range of 148 - 161 bpm. I could do that: it wouldn't feel like a super workout but it wouldn't be too boring.
Today after 33 miles (54 km) in my anaerobic range I really felt like my energies totally dropped in my last 10 km. This must be because of the glycogen that you mentioned. So, to reiterate, do you recommend that I do most my workouts in the aerobic range and only every now and then push it more?
Thanks!