Spreadsheet consulted again. I actually used my working heart rate as a reference point.
But as a %age of HRmax that would be about 80 - 85% which was close to marathon pace. I built up to this over a period of time, in increments of 5bpm. I got to the point that I didn't really need to look at my HRM.
It looked something like this...(hope this table works OK)
Mon 9 miles easy LA 130 Tue 9 miles LT 155 Wed 9 miles easy LA 130 Thu 9 miles LT 155 Fri 6 mile easy LA 130 Sat Sun 14 mile easy LA 130
Sorry for butting in unannounced, but spotted this thread by accident and wanted to comment. I haven't read all the comments or the previous thread, so perhaps this has all been said before but...
There were a group of us all running close to, but just over 36 mins for 10k. Then one of our group started HADD and he progressed over time to 33 mins 10k, sub 70 min for a half and sub 2:30 for a marathon.
Armed with that info we all started it and with great results. My improvements weren't as dramatic probably because I was a little low on miles, but managed to knock 1 min off my 10k PB and run a sub 17 5k and 6 minute mile a half. I was well pleased with that.
I found the most effective runs were long efforts at around 150/155 bpm, for 10 miles or so. Couple of these a week and rest low HR stuff were all that was needed. I used to plan it all out on spreadsheet, work out HRs and schedule races with tapering. Just looked back at all my training spreadsheets and can't help but think what a geek I was!
I started to mess around with it and used it as the base aerobic training of a Lydiard programme. Didn't really work any better, but the variation was welcome.
Illness last year, increasing age and lack of motivation means I am now a Has Been as one of my running colleagues christened me, when he started to beat me. But I can still run 17:40 as a v50 probably due to the aerobic base via HADD.