About a year ago I shelled out TWO HUNDRED QUID for a top level running gadget called a Stryd. This little footpod promises to deliver laser smart precision running dynamics data, facilitate power based training and – most importantly for me – deliver far more accurate distance data than GPS. Great, I thought, no more thinking you’re on for a PB at parkrun only to realise your GPS has wobbled and you still have 100 metres left. Some of my friends had Stryds already and reported they worked perfectly. But it seems that there is a problem with some of the newer devices.
For the first few months of owning the device I took what it said as gospel – the website proclaimed that it was accurate “out of the box” and should require no calibration. Most of the time it seemed this was true, but there were a couple of occasions that should have raised red flags – a suspiciously fast freedom parkrun at Mile End where I assumed I must have started too far back because my watch said I’d done 5k before the real finish line appeared, and a similar case at Lancing Beach Green where I assumed I must have had the turn around point wrong. I didn’t twig – I just trusted the Stryd because it seemed everyone vouched for its reliability. There were no official races at this time, but I was looking forward to trying it out for real. But when I did, I was in for a real shock, because it measured my 10k as 10.4k! I don’t recall every getting a result that far wrong with GPS, with the exception of races in built up areas with skyscrapers and the uncertified Fulham 10k which even the pacers thought was a long course. It was really quite annoying because it messed up my pacing completely and I spent more time doing maths in my head than enjoying the run. And then I thought back to the other oddities and started to wonder.
I posted for advice on the Stryd Facebook community but the admins (the manufacturers) did not approve my post and instead replied to me by email – their reply being basically “there’s nothing wrong with your Stryd, you probably ran the extra 400 metres weaving round other people or taking corners long”. I don’t buy this because
- it was a socially distanced race which I ran in 70 minutes. I overtook about three people the whole time.
- it was on narrow paths in a park. There are no opportunities for wide turns.
- looking at Strava, everyone else in the race recorded it between 9.9 and 10.1km on their supposedly unreliable GPS devices.
- it was a certified course put on by a reliable and trustworthy company
- when I used the Strava distance correction to see what GPS had recorded, it was just over 10k.
The same thing happened in several other races – but not every single one – so the second piece of advice I got from the manufacturers, to calibrate the Stryd on a track, didn’t seem like it would help, but I gave it a go anyway and ended up with a calibration factor of 97.6. The next day I ran a known 5k route and as you might have guessed the Stryd said I had done 4.88km which is 97.6% of the 5km my GPS watch had recorded. I tried to work out what would make the Stryd misbehave one day and be fine the next (hills? weather? my pace?) but I can’t really find a pattern. It’s just some days those kilometres are longer than others.
I was coming to realise that the fact I had only heard people praising Stryd’s accuracy is because the moderators get rid of all negative reviews on Facebook. There is, however, an unmoderated Stryd forum on the Stryd website where I found an entire thread of people who had the same problem (all people with the latest version who’d purchased it in the last year), and someone who works for Stryd had chimed in saying they were working on a fix and that it was due by the end of March. I was really pleased that it wasn’t just my imagination and that the manufacturers had realised something was wrong and were working hard to fix it. I decided to persevere until the next firmware update. But the end of March came and went and there was still no fix. People were starting to get impatient. I posted the thread as a comment on a post in the Facebook community and a different Stryd person, some bloke called Gus denied that there was ever a problem and that therefore there was never going to be a fix (quite the opposite of what his colleague had said – this makes me wonder if they tried to fix it, found they couldn’t, and then backtracked furiously). His reasoning for concluding there was no problem? Well, none of the people on the thread had conducted meticulous and stringent testing on the device and proved to him there was a problem. I asked what data he’d like me to send him. I could not believe the reply. He wanted me to
a) purchase a £100 premium measuring wheel (not just any old measuring wheel!) and a steel ruler
b) go to my local running track and measure it with said equipment
c) run several laps of the running track with meticulous attention to distance and send him the details
Those of us with any kind of scientific or mathematical background (or even a combined science GCSE from 20 years ago) are probably noticing a problem here. Well, a few problems. We’ll start with the frankly laughable request that I spend £100 and a whole morning testing his device for free. It seems he forgets we are runners and not scientists or gadget testers and just want our “accurate out of the box” device to work with no hassle. Then we’ll move on to the fact that he expects me to replicate a problem that occurs in one circumstance (races that could feature hills, a variety of surfaces and speeds, pauses and turns, and that are different every time) in a completely different circumstance (running the same short, flat, even paced, loop repeatedly). I think there’s a pretty good chance the stupid thing works just fine in these circumstances (presumably that’s how they tested it and why they have concluded it is so perfectly accurate). But I am not Mo Farah and I do not race on a track and I want mine to be accurate over a variety of courses. I want it to be closer to the advertised distance than GPS, not further away. 10k means 10k! There seems to be no other way I can convince him that the results I am seeing could possibly be a problem with the Stryd since he won’t accept comparisons with a measured course, with other participants, or with GPS as evidence because it’s “not scientific enough”. Dare I say that “Stryd is accurate!” is one of those unfalsifiable hypotheses we learned about in university. There actually isn’t a way I can demonstrate the issue that would be acceptable to him and therefore there will be no fix or replacement device for me or the many others who have eagerly waiting for it. Which is very frustrating disappointing because if it worked properly this would be a great piece of kit. Sadly out of the three races I’ve done this month, two came out way too long (I bet you can just imagine the disappointment of a further four hundreds metres appearing when you expect the finish line) and from today I’ve gone back to using GPS for distance. It may not be terribly reliable, but it doesn’t claim otherwise, and at least it is predictable in its unreliability.