Guys, looking for some advice from the folks who offered it earlier in the thread (Dr, Brian etc).
Have been a lurker for some time but would really appreciate some help now.
I find it impossible, even at virtually static pace (12:30 min mile) to keep heart rate at 75%. Can I reverse the theory and keep running at nearer 85% of MHR at the same pace UNTIL my HR comes down to 70% as I become fitter?
Brief info: age 36, 6ft, 12.5st, MHR 191 (actual test...the 220 minus age has me at 184)...generally fit, was a swimmer for three years until taking up running three months ago for the first time. Normally run 10miles about five times a week. I like having targets - so after 8wks of pointless huffing I looked into theories etc.
Hadd suits me, I have plenty of time to run.
Yesterday's 11.5miles was PAINFULLY slow, almost walking, and HR was an average of 160 (doing 12min miles.) Aaaaaaargh 
Today's 10miles was around 11:30 min miles and managed to keep HR to around 150 (but I was almost jogging on the spot at some points.) Between miles 8 and 10 I couldn't keep it below 160bpm. 
Ideal world: my 70% would be 133bpm, 75% would be 143bpm (both impossible, unless I walk, which is a no go) and 80% would be 153bpm...
Do I stick with the frustrating pace for however long it takes? If that is the answer, please say so. I have no problem sticking to it. Just worried that 12minute miles are not doing me any good. I have no problem running for 90mins or more (but then neither would anyone else at this pace!)
Regards,
Gus.