Could today be the day that I break my half marathon personal record set 14 years ago?
Last Sunday (13th August), I ran the 12th event of the 2023 Sportlink Grand Prix, the Great Yarmouth Half Marathon, a half marathon (13.1 mile) road race organised by Great Yarmouth Road Runners.
As per my pre-race article, my primary objective was to beat my personal record of 94 minutes and 20 seconds, set 14 years ago, back in 2009. I had only ever come close to this time in 2016, and since then have been hovering around the 100 minute mark. However, this year my training has been working wonders (thank you to TrainAsONE’s latest AI training algorithm, Artemis), enabling me to achieve personal bests at all distances raced (5 km, 5 mile, 10 km, 10 mile, and 20 mile). So confidence was high, but it would be a case of assessing the weather conditions on the day to ascertain how to run the race to get an optimal as time (as low as 90 minutes), whilst not ‘blowing up’ and missing out on my record.
A good performance looked to be on the cards…
The drive to the race was cloudy, but warm and humid, with the car indicating a temperature of 20° C. However, despite this when collecting my race bib at the event HQ, there was a cooling breeze which seemed to be taking any humidity with it. A good performance looked to be on the cards…
If all was perfect, I was aiming for a 90 minute time (a 4:16 min/km pace) and ‘at worst’ aiming for 94m20s (a 4:28 min/km pace).
My Race
The very first section of the course is a lap around a field and it takes over 600 metres until you reach the road for the remainder of the route. These two factors (running on grass, and being the start of a race) can make pacing difficult. The propensity to go out too fast is always too common. Consequently, I made an extra conscious effort to keep my pace in check for the 1st kilometre, and I was more than willing to allow fellow runners to overtake as we made our way around the field and then up the slight incline to the road.
My pacing effort was rewarded by a time / pace of 4:18 min/km. A great start.
I always find great anticipation in hitting the 1st km and checking my pace. On this occasion, my pacing effort was rewarded by a time / pace of 4:18 min/km. A great start. I felt comfortable and whilst warm, it was cloudy and the breeze was cooling.
The next few kilometres were gentling undulating, presenting no real difficulty, each being completed within a second of a 4:15 min/km pace.
…but my heart rate was now on the rise.
It was at the 4th kilometre point that the clouds began to dissipate and the wind began to die. Naturally it had no immediate effect, but I knew that this turn of conditions could call for a change in pacing strategy. I completed the 5th kilometre at another repetitive 4:15 min/km pace, but my heart rate was now on the rise.
By the 8th kilometre, the sky was blue and the wind was non-existent. It felt humid and I could believe it was the forecast 70% (humidity). I was still maintaining pace, but knew that this state of affairs would not last for long. Either it would have to cloud over and the wind return for me to continue at my current rate, else I would be forced to slow. I continued under the hope of the former.
My experience and sanity told me that today was not the day for the glory of a sub-90 minute time…
I made it to 10.5 kilometers (my mental, but slightly inaccurate half-way point) 7 seconds behind a 90 minute time. However, the conditions had not reverted and it was still hot and humid. My experience and sanity told me that today was not the day for the glory of a sub-90 minute time, and it was best to adjust expectations now, slow down and ensure I still obtained my personal record.
This I duly did, and allowed myself to ease off the pace to around 4:25 min/km. Knowing that if I could maintain that, I would still comfortably have a personal record under my belt. And apart from a couple of slight downhill stretches (one through the lovely estate of Somerleyton Hall) where I allowed myself to go with the terrain and up the pace, I stuck to my revised strategy for the next 7 kilometres.
…the toll of the humidity began to take hold.
It was during the 18th kilometre and an uphill stretch that the toll of the humidity began to take hold. My next 2 ‘k’ were the ‘wrong side’ of 4:30 min/km, but I was near enough to the finish that this little upset would not be a disaster.
Kilometres 20 and 21. I was back on track with 4:25 and 4:23 min/km paces, respectively. It was then a little 4:00 min/km sprint to the finish, and a finish time of 91m27s.
Analysis
Given the changes in conditions of the race, my adjustment to pacing strategy at the half-way point was the correct one. Overall, I don’t believe I could have ran that race much, if any better.
…going to show that such rules of thumb can be significantly error-prone.
It is commonly stated that you can run in heart rate Zone 5 for about 3 to 8 minutes. I ran in this zone for 50 minutes (54 % of the race), going to show that such rules of thumb can be significantly error-prone.
Below is a table summarising the predictions from various algorithms / sources, along with their error from my actual performance.
| Algorithm | Predicted Pace (min/km) | Predicted Time (mm:ss) | Error (seconds) | Error (percent) | Adjusted Error (percent) |
| Riegel (6 min Assessment) | 4:42 | 99:19 | + 472 | + 8.6 % | + 10.8 % |
| Riegel (3.2 km Assessment) | 4:32 | 95:38 | + 251 | + 4.6 % | + 6.7 % |
| Athlete Data Analysis Platform | 4:25 | 93:13 | + 106 | + 1.9 % | + 4.0 % |
| Running Watch | 4:22 | 92:05 | + 38 | + 0.7 % | + 2.7 % |
| Riegel (5 mile race) | 4:17 | 90:13 | – 74 | – 1.3 % | + 0.6 % |
| TrainAsONE | 4:16 | 89:52 | – 95 | – 1.7 % | + 0.2 % |
All the predictions do not consider the weather, rather they assume ‘ideal’ conditions. TrainAsONE calculates that my 91m27s time would equate to a 89m39s time under such ideal conditions. Consequently, I have produced a final column above that compares the predictions against this adjusted time.
There is no need to dwell on these too much. The important points to highlight are that the Riegel (race) and TrainAsONE predicted times were the most informative and useful for devising race strategy. And when adjusting for temperature / humidity, it would certainly appear correct that TrainAsONE’s sub-90 minute prediction would hold true.
Finishing Up
I got a 3 minute personal record!!! Who would not be chuffed with that!
Despite the conditions turning during the event, making it a tougher race, it was still fun. It was definitely the correct decision to change my pacing strategy at the mid-point – I wonder if a ‘younger me’ would have done so. Naturally, I am already looking forward to my next half marathon, and hoping for more favorable conditions to go even faster.
As ever, a big thank you to the race organisers, volunteers and all those involved. A great race. Thank you.
Till next time.
