DrDan, Good luck with the Tri - let us know how it goes?
Tortuga, Has MarkF says, stick at it. Patience is the key.
VTrunner, Best wishes with the rehab.
Interesting debate on the sub-lt runs. I do a short warm-up to these runs also, 10mins w-up and cool-down with 70mins at 80%. This is because of time restriction. I do most of my running at lunchtimes from work and the maximum time
I can take works out at 1.5 hours running time.
I think ideally a good warm-up say 15mins, plus a mile getting to the 80% would give more accurate results. I think that cardiac drift is most probably masked by the initial rise in the HR.
If we get to the predetermined HR BEFORE we start the measurement, I think the drift will obviously be higher, and therefore more difficult to eradicate.
I sometimes think about doing 20mins warm-up and cool-down and cutting the 80% bit to 50mins to get a "more accurate?" reading, but have never got round to it.
I think the most important factor is to get to the 80% level and hold it for as long as is appropriate. This will always give results and improvement.