20km van Brussel
It’s become somewhat of a yearly tradition for me to race the 20 km of Brussels. While such a hilly race is not a great setting to break personal distance records, it is nice to run the same race every year as some sort of benchmark. Besides that, I really like the race and it happens to start and finish within walking distance from my front door. As such, last Sunday I summoned my loyal supporters (i.e. my mum, dad and girlfriend), laced up my running shoes, headed towards the jubelpark and got myself ready to race the famed 20K of Brussels for the 6th time.
The Race
The 20km of Brussels is a fairly well known race in Belgium and, as such, I won’t bore you with too many details. Instead, you can study the course map below.
Click for a high-res pdf version.
One key fact worth mentioning about the race is that it is hilly. The first 11-12 kilometres go up and down, after which there is a fast and fairly long downhill part. Afterwards, around kilometre 16 or so, runners are faced with a steep climb, the dreaded tervurenlaan, which goes on for 1.5 kilometres. This hill, in particular, is a killer for runners who pushed themselves a bit too hard, as this long, steep climb drains the last bits of energy and mental fortitude you have left. Pacing yourself to have enough energy to climb this hill is key to the race. After this hill, the race continues on a moderate downhill until right before the finish, which involves a 100m climb on cobblestones.
Past Results
Over the past years, I have consistently improved my times. The most significant jumps happened between 2016 and 17, when I shaved 10 minutes of my time and between 2019 and last year, when I shaved nearly 5 minutes of my time. This last jump was significant for me, as it put me below the threshold to start in the first wave of the race.
| Year | Time | Links |
|---|---|---|
| 2016 | 1:51:54 | strava |
| 2017 | 1:41:37 | strava, report |
| 2018 | 1:43:08 | strava |
| 2019 | 1:39:44 | strava |
| 2021 | 1:35:19 | strava |
Goals & Training
Since I had to push myself quite hard to get close to 1h35 last year, and since I only managed to hold a 4:43min/km pace during the antwerp 10 miles, I figured I should not be overly ambitious: I would be happy if I managed to match last years time this time around.
In spite of my lack of ambitious goals, I took my training seriously. From March on out, I consistently ran 4 times a week. After running the 10miles of Antwerp, I ensured my long runs were around 20km long. I planned to introduce some actual speedwork into my training (which I also did in preparation for the last 20km of Brussels), but I had to mostly drop this idea due to consistent issues with my left Achilles’ heel. These issues were not too serious, but they made me cautious of introducing additional strain on my body nonetheless. Unrelated to the 20km, I also started going for the occasional swim somewhere in the month of May. My full training calendar can be seen below.
| Week | Mon | Tue | Wed | Thu | Fri | Sat | Sun |
|---|---|---|---|---|---|---|---|
| 1 | 9K | 10K | Swim | 11K (threshold) | 18.5K | ||
| 2 | Swim | 7K (recovery) | 9K | 11K | 19K | ||
| 3 | Swim | 8.5K (recovery) | 11K | 11K | 20K | ||
| race week | Swim | 9K (recovery) | 6.5K (recovery) | Race |
Including race day, I ran around 184km in May, which is, apparently, a distance record for me.
Diabetes Management Changes
10 days prior to race day, I started using a new insulin pump and continuous glucose monitor (CGM) system to manage my diabetes. I generally try to avoid major changes this close to a race, but unfortunately, this was unavoidable.
A major change introduced by my new pump is the introduction of “Control-IQ”, which is a system that automatically attempts to correct my blood glucose levels by adjusting the insulin delivered by my pump. To explain it in layman’s terms, the pump will automatically give me extra insulin when it predicts my sugar levels will be too high (thus making my blood sugar go down), if the pump predicts I will be too low, it will reduce the insulin it gives me to bring me back up to a normal level. This feature is a game changer for my personal diabetes management. However, major game changers take some time to get used to. Since I only had 4 runs to get used to my new “setup” (two of which were recovery runs) I was starting an important race with a pump I had very little experience with.
Important to know here is that being active significantly enhances the effect of any insulin in your body: 0.01ml of insulin when sporting has 4 times as much of an effect on my body as the same amount of insulin administered when I am sedentary. This means that sporting with any insulin in your body makes it incredibly easy for your blood sugar to drop too low (which is a bad thing™). When you combine this with a system like Control-IQ that automatically administers insulin when your sugar reaches high levels, you can easily end up in a situation where your sugar levels inadvertently drop too low very fast (which is a very bad thing™).
In spite of this, I still chose to run with Control-IQ enabled. I did this for three reasons. First, the system can lower the level of insulin to prevent lows, which is ideal when racing. Second, I made adjustments to the “sport mode” of the system which seemed promising: during my last run before the 20K, I did not drop too low even after the system decided to correct my blood sugar. Third, getting too high when running is also not great. I often ran my races too high, which lead to issues. Last year in particular, my legs cramped up after 13km or so, which made the second part of my race much harder. Therefore, I did not mind some mild corrections which would help keep me in a reasonable range.
Of course, since I am spending so much time explaining all of this to you, you can probably guess something eventually went wrong. *dramatic music*
Race Day
I got up at 7, ate some cereal, freshened up and started getting ready for the race. As expected, the weather seemed perfect for running. Before I knew it, it was 9 and me and my girlfriend left to the race venue. I checked my sugar before leaving; it was at a perfect value for running: a bit too high, but not overly so. Unbeknownst to me, this is when control-iq decided to give me some insulin to compensate for my high sugar value.
In spite of some delays I actually managed to get to the race venue on time (I usually arrive at the very last minute). Once there, I took my time to run a few warm-up laps after which I ate a banana. This would gradually release some sugar into my system, which should keep me at a perfect value for running. I sorted into my corral, greatly enjoying the fact that I didn’t need to queue up to get to the other side of the park this year. Once there, I decided to check my sugar once more before departing. To my surprise, I saw my sugar levels were lower than before my warm-up and slowly dropping. It seems like the correction administered by control-iq was enough to cause my sugar to drop when combined with a walk to the venue and a few warm-up laps. At the time I did not know why I was dropping. I decided to drink one of my gels to cause my sugar level to go back to the desired, slightly too high levels.
While I was worried about this, I did not have that much time to worry as it was nearly time to go. When the bolero by Ravel started playing, I set up my watch and got ready to set off. One bolero and one rendition of the Brabançonne later the gun went off and we all started running while “Ode to Joy” started playing. Or well, we sort of did. As is tradition, a bottleneck appeared before the start line, so I took my time walk-jogging to the finish line. Once there, I hit the start button on my watch and we were off!
As usual, the first kilometre or so was pure chaos. This time was spent weaving through the crowd, trying to find a spot where I could run my own pace. This was not that easy as the first few meters of the course are quite narrow. I also knew my family would be waiting close to this point, so I tried to stay on the right where I would have a better chance of saying hi as I passed by.
I evidently don’t like weaving.
Luckily these first metres passed without incident. After I passed my little crew of loyal supporters the course opened up which gave us all some more room to manoeuvre. By the time the race reached its first climb, very little weaving was required. At this point I also realised I was running quite fast. Since I was worried I might blow up if I went too fast at this point, I slowed down a bit and tried to find somebody running a bit slower to tail for a bit. I didn’t really find anybody running an appropriate pace, so I decided to keep an eye on my heart rate to make sure I wouldn’t overdo it. I consistently stayed between a heart rate of 170 and 180, which seemed to work well. I was not sure if I would be able to maintain running at this heart rate, but I was feeling fine, so I carried on.
| km 1 | 4:01 |
| km 2 | 4:22 |
| km 3 | 4:17 |
| km 4 | 4:51 |
When I passed the 4km sign I noticed I has passed the previous km markers without noticing. I pushed the lap button on my watch (I lap this race manually to avoid accuracy issues in the tunnels) and was surprised to hear that my pace during this first lap was 4:23. I was very worried about blowing up, so I kept a close eye on my heart rate and made sure I did not exceed 180bpm. When I did, I made sure I slowed down until I was back at a more manageable level. Since we were consistently climbing, the splits for this part of the race are a bit slower. However, my watch told me I was consistently running faster than my planned pace.
| km 5 | 4:46 |
| km 6 | 4:29 |
When I entered Bois de la Cambre, I remembered the aquarius drinks that would be handed out around kilometre 8 or so. I figured this was a good point to get some extra sugar if I needed it, so I took the time to check my sugar levels, which were high and rising. I was delighted to see this and decided to skip the sugary drink and check my sugar again once the race would go downhill, a few kilometres later.
Somewhere in the forest, the 1:30 pace group caught up with me. This was to be expected: I was aiming for 1:35 and started ahead of them in the start box; the 1:20 group had already caught up with me some time before. Some time after they passed me, I noticed they were not that far ahead. I checked my watch and I noticed I was well ahead of my 1:35 plan. At this point I figured a PR might be in the cards. However, I was still worried about blowing up, so I stuck to a pace which would keep my heart rate in an acceptable range.
I was really enjoying the race at this point. A PR was in the cards, I was feeling good and my sugar seemed to be fine. Carried by some uplifting tunes and the hope for a PR, I sped out of the forest.
| km 7 | 4:42 |
| km 8 | 4:33 |
| km 9 | 4:06 |
| km 10 | 4:21 |
| km 11 | 4:33 |
After cresting a hill, I knew the race would go downhill and decided to check my sugar for my peace of mind. I was dismayed to see that my sugar was in free fall. I was back to the level I started at, and the trend arrow indicated I would keep on going down. Apparently, Control-IQ had decided to give me some insulin when my sugar was rising rapidly. My sport settings are obviously not in tune with my body yet, because this made my sugar drop like a brick. To its credit, once the system saw that my sugar was dropping like crazy it cleverly decided to stop all insulin deliveries.
With a worried heart, I drank my second and final gel and decided to consume any source of fast sugar I could get my hands on. As if I summoned her, I saw a lady next to the course handing out slices of orange a few minutes later. I gratefully took one of these and sucked out all of the juice like some sort of sugar chasing gremlin.
| km 12 | 4:39 |
| km 13 | 4:15 |
A few minutes later, I saw another lady handing out orange slices. Again, I greedily accepted a slice and resumed my gremlin ways. I also decided to try to signal my girlfriend (who I would see in a few kilometres) for the extra sugar tablets I knew she was carrying to give me some options in case my sugar would keep on dropping.
Besides my concerns about my sugar I noticed I was still running very fast compared to my usual pace. Every time I pushed my lap button I was mildly surprised to hear the pace I ran for the last kilometre or sure. At some point I’m pretty sure I thought the kilometre markers were placed too soon, which would explain why my watch said I was running so fast.
| km 14 | 4:33 |
| km 15 | 4:14 |
A few minutes later I arrived at Hermann-Debroux where I would see my loyal crew once more. While I was very grateful to see them I did not really show this. Instead, I was gesturing to an empty packet of gel and yelling “DEXTRO” in the hopes to get some more sugar. Of course, I passed by fairly fast, so my partner did not have nearly enough time to fish the dextro’s out of her purse and give them to me. I sped on and resolved to not look at my sugar levels from this point on out as they would only make me anxious and I could not really do anything about them besides eat any sugar I could get my hands on.
Patiently waiting.
The next few kilometres were fairly uneventful. I still refused to believe the splits my watch was giving me and kept an eye on my heart rate to stay at an appropriate pace.
| km 16 | 4:23 |
| km 17 | 4:32 |
By the time I arrived at the tervurenlaan, I was still feeling good. Moreover, my watch said I was more than 4 minutes ahead of my goal time. At this point, I accepted that I was going to absolutely destroy last year’s PR if I didn’t royally screw up. I also considered if I could breach 1:30 at this point. However, I told myself that a 1:30 goal is way out of my reach and focussed on sticking to a manageable pace. I evidently still had enough left in the tank as I climbed the tervurenlaan at my planned pace without much issue. I also found another lady handing out orange slices, which I gladly accepted.
Doing fine compared to some of the people around me.
| km 18 | 5:02 |
| km 19 | 4:33 |
Once I crested the tervurenlaan I noticed I still felt fine. Since there is no reason to hold back at this point, I gradually started to accelerate in the last straight line towards the finish. Half a kilometre before the finish I saw my family one last time. My mum yelled at me that I was doing really really well. I checked my watch and noticed that I had been running for 1 hour and 28 minutes. With the finish in my sights I finally believed that I could breach 1h30 for the first time if I hurried.
Still looking surprisingly good so close to the finish.
At this point I started pushing everything I had left out of the tank. I gritted my teeth and sprinted up the cobblestones, determined to reach the finish before the 1h30 threshold. I rounded the final corner, checked my watch, saw a 29, and let out a fistpump as I crossed the finish.
| km 20 | 4:08 |
Results
My watch showed a time of 1 hour 29 minutes and 16 seconds (strava). My official time was 1:29:15. That makes the updated table look like this.
| Year | Time | Links |
|---|---|---|
| 2016 | 1:51:54 | strava |
| 2017 | 1:41:37 | strava, report |
| 2018 | 1:43:08 | strava |
| 2019 | 1:39:44 | strava |
| 2021 | 1:35:19 | strava |
| 2022 | 1:29:15 | strava, report |
Since I was aiming to match last year’s time I was extremely happy to unexpectedly breach 1:30 for the first time. What’s more, I still felt fairly okay after the race. I checked my sugar which went down to a perfect level. Evidently, Control-IQ managed to keep me conscious by turning of all insulin delivery. That being said, if the race had lasted a bit longer I might have really been in trouble. Of course, I would have brought additional supplies for a longer race. A post-race banana kept me at a good level as I walked back home with my family.
In spite of the stress caused by my sugar-level related worries I am very happy I decided to run with the Control-IQ system enabled. While I still don’t know how I exactly managed to cut more than 5 minutes of my time, I do think that running at a good sugar level contributed significantly to my success. Besides that, I am sure that the perfect conditions also helped. Of course, I should give myself some credit. I am sure that consistently training 4 times a week for several months helps too. It felt very satisfying to be rewarded with such a nice time after working at it for such a long time. This serves as a nice motivation to stick to it and to increase my weekly mileage in the future.