Havent worked out HRmax as yet but at a guess I would say its probably 180. based on that my 75% would be 135. Had a half hr on the mill again but this time set it to 6mph. I knew outdoors it would be difficult to estimate a consistent pace for this test,
It seems to show an average of 131 which means I need to do my slow runs at 10 min miles. I'll try a couple of these slow runs a week with an interval and normal paced longer run at weekends and see how it goes!
Thanks guys - reassuring. The trend was a slow increase in speed over the first halh hour culminating in a 2 min sprint then recovery. Glad you think it looks OK. It does appear though that even a steady slog at 7mph will see a gradual increase in heart rate. The 5 - 20 min section shows an increase from 139 to 157. that was pretty much my half marathon pace so would be interested to see how high it went at a prolonged period at that pace.