Jeff has the best answers to questions like this......though sometimes
I don't really know what he said.
For a mid packer like myself, I don't think VO2max is very usefull
information. I find that percieved effort and heart rate to be my best
means of feeling in control of my training. Not that I really benefit
all that much from any of the data I collect on my running.
I suspect most of it is piece of mind and a hint that I have some
sort of control. The one thing I find with heart rate is that I can
sometimes "get over" a bad run when I see the heart rate was quite
high, which tells me the body is tired. Also there are times when I
"feel" I am running to my max and the brain says I can't put in any
more effort....but I look at my heart rate and see it is not peaking,
it helps convince me that I can push harder and I usually do.
The one time heart rate really helped was when I ran the first 50K
and used heart rate to keep myself from putting in too much effort
during the first 2/3 of the race. I can say that it worked very well
and allowed me to finish strong.
What this all boils down to is, use what ever means that helps you in
your runs.