My Centurion Grand Slam in Numbers
Posted by Ed on March 30, 2022
In 2021 I completed the Centurion 50-mile Grand Slam, a series of four 50-mile races spread across the year. With the start of the 2022 Slam just a few weekends away, I thought now might be a good time to look back on my Grand Slam and analyse some of the data to see how things went.
As a self-confessed spreadsheet addict, I keep quite a detailed Google Sheets on all my runs, with some nice visualisations to help me better get a sense of how things are going. I did a more detailed dive into each race in the Grand Slam in a separate spreadsheet, pulling data from my GPS watch as well as the Centurion website.
Please note, this is not a race report. I’ve already written up a quite lengthy race report for each race on this blog – if you’re interested in that kind of thing, click here.
Pace
Unlike shorter distances, it’s very difficult to manage a negative or even split in an ultramarathon. Running for hours on end just slows you down, it seems. However, research does suggest that the best ultrarunners in terms of overall performance have one thing in common: they slow down the least.
That might sound obvious, but it’s actually not as simple as just saying “the best runners run fast.” In order to slow down the least, you have to start out at the right pace. This is difficult in any race, but it gets more and more difficult to judge as the distance gets longer – it can be very hard to imagine what your pace will look like after 9+ hours of running when you’re standing at the start line, fresh as a daisy.
The graph below is a representation of my average pace across all four races. I’ve tried to eliminate the impact of elevation gain by using Strava’s gradient-adjusted pace stats, and by smoothing out each data point over a 5k average.
There are some discernible points of interest, such as the 40k mark in the North Downs Way 50 when Box Hill reared its ugly head, or the fact that I managed a (relatively speaking) sprint finish in each race. But generally, it’s a bit of a tangle to decipher. Visualising the trend for each race brings the bigger picture more into focus.
Here, the similarities between each race stick out more than the differences. Namely, that my rate of depreciation was pretty much uniform for all four. Whilst I started out slower in the Wendover Woods 50, for instance – no surprise given the elevation involved – I slowed down at more or less the same rate as the altogether less lumpy Chiltern Wonderland 50.
Interestingly, I started out the CW50 and the South Downs Way 50 at essentially bang on the same pace, but slowed less in the SDW50 overall. Unsurprisingly, given that it is a mile short, the SDW50 was my fastest race, but it was the NDW50 where I achieved my fastest average page, of 6:55/km (around 11:05/mile). This shows in the chart above, where the NDW50 line is below all the others until the 60km mark, where it only barely creeps above the SDW50.
Position
Pace is all well and good, but comparing each race in the Grand Slam is a bit like comparing apples to oranges. They are all so different in terms of terrain, time of year, elevation gain, that it can be hard to extrapolate any noticeable pattern from such a small amount of data.
Luckily, I have access to a much larger amount of data, in the form of Centurion’s results for each race. Centurion publish amazingly detailed results, listing not just your overall position, but your gender and age category position too. And they don’t just do this for your overall finishing time, but for each aid station along the way.
This gives us access to the most relevant data source when it comes to analysing how each race went for me – namely, how it went for everyone else!
The graph below, then, shows my overall position across the course of each race. Each data point represents an aid station along the 50 mile course.
I must admit, this is a really satisfying graph for me to look at, because it correlates exactly with what I instinctively felt was happening during each race. I always started conservatively, allowing plenty of eager-looking people to overtake me for the first few hours. Then, in the second half of the race, I slowly overtook people myself.
There are only a couple of instances where the graph goes the other way, such as towards the end of the SDW50. This was the first race of the Slam (and my first proper 50 miler, solo run aside), and I distinctly recall feeling euphorically broken as I walked out of the penultimate aid station in the late spring sunshine. But as you can see, I did manage to pull myself together and overtake a couple of people in the last few miles.
I think the biggest shock for me is the steepness of the curve for the WW50, where I passed through the first aid station in 171st place and finished 56th. I don’t know if this is a testament to me doing a really good job pacing, or a lot of people really misjudging it. I suspect it’s probably both.
Takeaways
Can we learn anything from these graphs? Well, yes – and no.
It’s definitely the case that running conservatively at first and aiming to slow down as little as possible is a great strategy, especially if you are running all four races in the Grand Slam and don’t want to burn out on any of them. There is no better feeling than surging towards the end of a race, or even just holding onto a decent pace; conversely, there is no worse feeling than blowing up.
However, what worked for me won’t necessarily work for you. Your own running history, style, the conditions on the day – all of these will affect how a race pans out, much more than any strategic approach you bring to it. As Mike Tyson once said, “Everybody has a plan until they get punched in the face.” And a 50-mile run is more or less guaranteed to throw you a few punches.
What matters is the experience you have, which teaches you more than numbers ever could. I really, really enjoyed the Grand Slam, so much so that I’m running the WW50 again this year, and considering the SDW50 and/or the CW50 for 2023. So if you’re considering entering any of the races or all of them, I highly encourage you to do so!
