blog geeking running


Ok, this is probably a lot to take in with one picture! I’ve had a look at the last 12 months worth of marathons and training data and tried to capture it on a plot showing how training has improved my performance. Firstly I’ve focussed on the relationship between heart rate and speed. This is a well established linear relationship and as such you can easily plot out the line for yourself with just a few runs at different steady speeds. Now the goal of training can be achieved with a number of approaches, but the end result will be the same – your heart rate will get lower at a given speed, in-fact at all speeds! This means it can be used as an excellent indicator of fitness. The gradient of this line has an interesting unit, beats per kilometre, and as your body adapts to more training load the gradient will start to go down (and vice-versa I’m afraid!). So whatever your approach to training, you want your beats per kilometre to go down. Still with me? Good!

So bearing this in mind I’ve plotted the fit of four weeks worth of running before the taper of each of the 6 marathons I’ve run in the last year. The fit gives me a line that should then in-turn give me speed estimates for different heart-rates. Now after running several, evenly-paced, marathons I know I can sustain a speed corresponding to an initial heart rate of around 168-170 bpm (this number will be specific to each individual but I’m finding it’s in the range 20 – 28 beats less than your maximum). The progression of the lines from each marathon shows that the increased training load in each bout (averages over 4 weeks shown in the legend) does indeed improve my beats/km and with it all my race times. Putting in half marathon and 5k results would clutter this plot even more so I’ve stuck with marathons, plotting points corresponding to the average speeds I managed to finish each marathon with the half-split noted for reference. As you can see they don’t quite match the interception with the heart-rate/speed lines at 169-170bpm but they come fairly close and the trend follows the lines nicely. The end result is that with even a small dataset of runs including heart rate you can get a pretty accurate idea of your speed and fitness and track its improvement (and decline too which I know all to well from last Christmas, I’ll save that particular plot for another time!).