Am pleased to report that, even though I have been feeling as if there was no improvement whatsoever, my heart seems to think differently. I was convinced nothing was happening, despite my interval training interspersed with steady runs. But when I went to the doctor's to get a medical certificate (necessary in France where I live, even if you want to join a simple 5k race!), she measured my resting HR at 48. When I checked it first thing in the morning about 3-4 months ago it was 58. So am very pleased the effort has paid off and thought I would let you all know in case you think you are not improving - you probably are!. I guess the gradual nature of training and improvement makes it hard to spot sometimes!.