So I thought I would try and increase my cadence, and "cadence increasing running plan" didn't throw anything out. I also knew from experience that if I just did a 5K unstructured (i.e. trying harder) I would fail.
I decided to run 1st, 3rd and 5th K at between 160 and 170 regardless of pace or HR and run the 2nd and 4th Ks as recovery, regardless of cadence or trying to get my HR down.
Result: connect.garmin.com/modern/a...
Very pleased with the result - you can clearly see where my cadence increased and there are a few download trajectories of my HR on the even Ks - not as much as I had hoped for but that will improve with time.
It was also encouraging to note that my 'recovery K' cadence was a teeny bit higher than normal.
It was interesting how much extra effort that extra cadence cost - perceived and HR. I did speed up unintentionally during the increased cadence. I can't run a 5K at that increased cadence yet, but within a month - almost certainly.
Next run will hopefully be a long 7.5K 'aerobic' HR run where I am not going to worry too much about my cadence.
I plan to put this workout at least once a week.
Anyway, off to enjoy my post-run peanut butter on toast