Runners mostly focus on data, metrics, and statistics - the likes of mileage, pace, heart rate, heart rate zones, thresholds etc. However, the machine that powers our runs is biological—our hearts, lungs, brains, muscles, bones, tendons, and ligaments. It doesn’t rely on data but rather on something more organic: the concept of effort of the run. In this article, I write about the importance of understanding the 'feel' of the run, how to master it, and the benefits emerging from that.