The 100km de la Somme was the first ultra I ran with a heart rate monitor and it opens up some new opportunities to assess my form during the race and afterwards, too. Coupled with looking at the cadence data – at least when I am not mixing them up in training – it gives me a good idea of my form and feel during the course of the race.

In the race yesterday I managed to keep my heart rate under control throughout. This was part of the game plan, of course, and I didn’t want to spend much time outside what is a comfortable endurance zone. A little tempo? Of course, that’s to be expected. But the longer I could stay in an endurance zone the better as it would leave me better able to dig deep when I needed to.


As shown in the breakdown of the heart rate data above, most of my time was spent in zone 1 and zone 2. All up, 70% of my race was at a heart rate below 157 beats per minute. I’m sure that most of the nearly-one-hour I spent in zone 1 was when I was walking or at an aid station for a minute or two, so I’m quite happy to have managed to keep my heart rate in the moderate zone for the largest part of the time I was running.

The time in the tempo zone (zone 3) was primarily the 30km I ran between the 20km and 50km points – indeed, it came just before I started feeling bad in that lead up to the turnaround. Perhaps something to keep an eye on next time I am racing?

In contrast, during the final 25km when I was laying down my fastest splits of the race I never went above 159 beats per minute for any of the kilometer splits. Though the cut off for tempo according to my maximum heart rate is meant to be 157, I know that if I keep it under 160 beats per minute I am doing fine, and I managed to do that in the closing quarter of the race.


The cadence I was running at – in the pink in the chart above, with the blue being the pace – was also pretty good.

The average cadence was only 166 steps per minute which is lower than the 180 I aim for. However, that 166 average includes time walking and time in aid stations taking very few steps, too. If those times are excluded, I pretty much stuck to 180 throughout.

That flattish line across the top of the cadence data that I held for most of the first 50km and then every time I ran in the final 50km? That’s smack on 180 steps per minute. I wasn’t always running fast but I was running well, keeping my step rate up, and taking small steps to keep things nice an efficient.

For what it is worth, I didn’t look at my cadence during the race but I did keep an eye on my heart rate from time to time. It’s another data point (besides speed and distance) to take into account when assessing whether to push hard or to ease it off, and I’m glad to have access to it while on the run.

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