I like heart-rate-based running training for three reasons. It tracks your internal effort far better than running on pace does. It lets you train in physiologically meaningful intensity zones, which pace alone cannot do. And it gives you a real way of tracking your aerobic fitness over time. The trouble is that heart-rate training is also deeply confounding, and the moment you start reading about it on the internet, it gets worse rather than better. So what I want to attempt here is to cut through the noise and make heart rate training as clear as it currently can be. ...

Part one of a series. This is the overview — my personal history as an introduction to the series. Follow up articles will be technical deep dives into various aspects of fast and sustainable running (heart-rate zones, zone 2 vs zone 3/4 running, the economy of run-walk) and articles detailing my own personal N=1 experiment. I have never been a patient runner. Left to my own instincts I run hard, because running hard and pushing myself is what I enjoy. However, for the better part of a decade the dominant wisdom in endurance running has been the opposite of my instinct: slow down to get fast. I tried to follow that advice faithfully. It worked, in the sense that both my distance tolerance and my times improved (albeit slowly), but it also made me quit running out of sheer boredom. So ultimately it didn’t work for me. This is the story of my search for the holy grail of running that gets maximum results, minimises injury risks and most importantly, keeps me motivated. How I started out running hard, then discovered running slowly, lost the will to keep doing it, and finally found a way — run-walk intervals — to train fast and stay in one piece at the same time. Most of the numbers here are my own, pulled from my Garmin and a current (messy) experiment on myself. Where I lean on the science, I have tried to source it for further reading. ...