I am completing Eric's marathon training program & last night my training consisted of;

WU 20min in zone 1-3 + 5 X 30sec building speed.

MS 8 X 15 sec steep hill repeats with 2-3 min RI.

As where I am working at present in Toowoomba Queensland, steep hills were a bit away & the light was fading so I modified the MS of this session, really enjoying it.

The modified repeats consisted of 10 X 30sec repeats with 1min RI. Once I had established a few metrics, eg, the distance travelled in the 30 second sprint and 1 minute recovery. And once I had established some assemblence of consistency, I switched my watch to HR and tried to attain and maintain the same effort and therefore HR for each repeat, by HR alone.

My goal was to have a maximum HR of 140bpm by the end of the effort and to reduce my HR to 115bpm during the recovery before the next effort.

It was fascinating to see how I could control my effort HR by adjusting my I minute recovery speed until towards the last repeats the accumulated effects of the session required me to walk so as to maintain my effort HR.

I was so engrossed in the "experiment" that I lost count of exactly how many I did but I think it was 13 or 14 finishing in the dark without a head lamp. If it wasn't dark I think I would have continued, I will definitely do this again