Pacing yourself is always an important part of running a successful race. You don’t want to go off too fast and suffer through the second half, or feel so fresh at the end that you wish you’d pushed harder in the early stages.
To pace yourself correctly, you need a target time, which should ideally be based on your performance in training rather than a neat number plucked out of thin air. The best sports watches all now provide race predictions for the most common running events — 5K, 10K, half marathon and marathon — and Strava will also do the same, with the watches and app basing these predictions on your training history.
I’ve been training hard for the Brighton 10K and checked my race predictions from Garmin and Strava ahead of the race, as well as asking my coach what he thought I could run. Here’s what they said, and which was most accurate.
Garmin and Strava race predictions
I have been using both Garmin watches and the Strava app for many years, so they have a lot of training history as well as past race performances to draw on with their predictions.
Garmin says it uses the estimated VO2 max you get from its watches, plus training history, to provide a race prediction. I have had my VO2 max tested properly using a gas-exchange mask, and Garmin’s estimate of 69 is about right; coupled with my training history, I expected a good prediction from the Garmin Forerunner 970 I’m wearing at the moment.
Garmin believed I could run the 10K in 32:05, which I assume is a prediction based on perfect conditions — both in terms of the weather, the course of the race not being too hilly or twisty, and my physical condition on the day.
I’ve noticed that Strava’s race predictions are a lot more volatile than Garmin’s, in that they can change quite a lot based on one run. Strava says it uses 100 data points, including all-time run history and top performances, to make its predictions, and doesn’t use theoretical VO2 max estimates.
Ahead of the 10K, Strava’s prediction was very close to Garmin’s, with the app saying I could run 32:03 for the distance, again, presumably in perfect conditions.
As an extra data point, I also checked my Coros Pace 4’s prediction. I haven’t used Coros watches continuously for as long as Garmin and Strava, but it did give a similar predicted time of 32:09.
Finally, I also asked my coach, Andy Hobdel, what he thought I could run on the day. I’ve worked with Andy for around seven years, and he was more optimistic, suggesting a time of 31:55 was on the cards.
Which was the most accurate?
Conditions were close to perfect on race day. The Brighton 10K is a fast, flat course with just three turns, and it has a strong field of runners, so I knew I’d have people to run with all the way, which definitely helps to maintain a fast pace.
The race is on the seafront, and in the past, at the same event, the wind has made it difficult to run fast, but on this day, the breeze was fairly gentle and not a factor. The only potential prediction confounder was that I woke up with a sore throat on the day.
I felt pretty fine overall, though, so I went all out in the race and hit the halfway point in 15:41, way ahead of the pace for my predicted times.
The second half of the race was tough, and I did slow down, but getting involved in a four-way sprint finish helped to keep me going, and I ran 31:54 for a big PR (or PB, as we call it in the UK).
That means that Strava was the closest to my actual time ahead of the predictions Garmin and Coros gave, but all three were pretty much on the mark.
I imagine watches also don’t account for the illogical level of importance runners like myself place on finishing in under a minute mark — 31:59 feels a lot faster and better to me than 32:01, so I pushed hard to go sub-32.
The best prediction of all came from my coach, who was just one second out, which perhaps goes to show that while sports watches and other training tools are good, you still can’t beat the real-world experience of an expert.
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