Oh yes! Big gains, but not so much at the high end. OTOH, the high end comes up by far the quickest. Nancy's speed on her trainer at VT1 is up from 7 mph to 11. My speed on my resistance rollers is up from 16.5 to 18.2.

Carmichael puts it this way (paraphrased): Imagine you have a straight string of all the intensities, from zero at one end to 100% at the other. When you work at a particular intensity, you pick up the string at that point and make a graph of improvement something like that. However when you increase your VO2max, the whole string raises, since power at every intensity is a function of VO2max.

I rather doubt that it's that simple. Experience says that it is not, at least in terms of endurance. When we have done climbs recently of up to 8 minutes in zone 5, it's been easier for me to hold the intensity than it has been in years. And for Nancy, it's now possible. I'm not sure that we're faster in zone 5, at least not yet, but we passed a relatively fit single on a 15% grade the other day.