Back when Apple announced watchOS 27 back in June earlier this year, there was one new feature that piqued my interest more than the promise of a smarter version of Siri or a Workout Buddy that now operated more standalone. Apple revealed that it was delivering more accurate distance tracking during walks and treadmill runs. It’s primarily doing that by making improvements to the algorithms that help to calculate the distance covered when you step onto that belt.
It’s website states that ‘improved motion tracking algorithms help measure the distance of your treadmill runs and walks more precisely straight from your wrist.’
As a runner that does his fair share of runs on a treadmill (and not just because it’s got cold outside — treadmill running is great for specific pacing and incline drills), I liked the prospect that the best smartwatch’s indoor activity credentials could now match its very solid outdoor performance — which I tested on the London marathon course’s infamous GPS black spots.
So, has Apple actually managed to deliver more accurate distance tracking for indoor runners? I’ve been spending the last couple of months testing the feature across the best Apple Watches — including the Apple Watch Series 12 and Apple Watch Ultra 4 — to find out.
How I tested
I began my testing using the beta versions of watchOS 27 running on the Apple Watch Ultra 3 and the Apple Watch Series 11. When watchOS 27 was given a public release, I also strapped on the Apple Watch Ultra 4 and the Watch Series 12 to see how Apple’s latest smartwatches fared indoors.
I didn’t have my own treadmill (or indeed, have the room to house one), so I relied on the treadmill at my gym. While I did my best to stick to the same treadmill for these test runs, that wasn’t always possible. That did mean I’d be stepping onto treadmills of various conditions and belt wear, which does have an impact on the reliability and accuracy of the treadmill distance tracking feature.
With the Apple Watch strapped alone to one wrist, I had a Coros watch on the other paired to the Coros Pod 2. This foot-worn pod is designed to track distance, among other metrics, and was an additionalng distance than the motion sensors that usually do that from the wrist. I used the foot-worn pod as a control device, the same way we use the best heart rate monitors to test the readings from smartwatches
With watches on wrists and the pod on my feet, I captured a range of runs covering different paces and distances. That included short one-mile test runs, steady hour-long runs and interval runs during which I mixed up my pace.
I stuck to the same incline for all runs and used Apple’s own Workout app to track the workout. Apple suggests tracking an outdoor run of at least 20 minutes to calibrate the watch and help those algorithms do a better job of understanding your stride length, and in turn, deliver more accurate distance tracking. I did that with each Watch I tested.
The results
On the early runs in my testing using the Apple Watch Ultra 3 and the Series 11, I found a difference of about 300 metres (0.3km) from the distances the treadmill and Coros Pod 2 reported. If I’m looking at that difference in terms of a longer distance race such as a marathon, that’s quite a small difference. If we’re looking at that difference over a shorter distance race such as a 5km, then it might be the kind of difference that mattered.
When I switched to testing with the publicly available version of watchOS 27 with the Apple Watch Ultra 4 and the Series 12, there tended to be a difference between the treadmill and watches of roughly 200 metres. Again, that’s a very good performance and a small difference when you’re banking a longer run.
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Apple Watch Series 12 distance |
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The improvement in distance tracking should, in theory, have a positive impact on capturing your running pace. While I found the pacing data to in general be similar to the Coros Pod 2 and the treadmill, there were times I felt the Apple Watches struggled to register faster sections of certain running sessions and typically was more noticeable during interval-style sessions.
This is generally where treadmills can struggle too, and I’m not convinced the various Apple Watches always got a good grip of my real-time pacing.
Is the Apple Watch fit for the indoor run tracking job?
After hitting double-digit treadmill runs across a series of Apple Watches that promise more accurate distance tracking for indoor runs, I can say that I never saw the Watch and treadmill entirely match up. What I did see was that those Watches weren’t far off. reporting similar distances to the kilometers listed both on the treadmill and on the Coros Pod, especially on steady or easier paced runs. However, they were never exact.
Like most watches and badly-calibrated treadmills for that matter, the pacing during those runs did feel off and made using the Apple Watch for faster runs more problematic. I do feel that those algorithm tweaks will be more appreciated by those choosing to do their walking indoors, and are mainly focused on the distance they cover during that inside walking time.
If I was choosing to track my runs indoors, I’d still make sure I was performing that 20-minute outdoor run calibration to get the most reliable data. I’d also say that having a footpod sensor like the Coros Pod 2 or a Stryd that captures your stride data closer to the point of the body that’s actually doing the moving will get you a better level of accuracy. While the Coros Pod 2 is tied to Coros watches, the Stryd does work with the Apple Watch.
What it really showed is that if you care about accurate distance and pace data, getting outside and putting the onboard GPS sensor will still be the best way to get you that. It will also give that indoor running time a boost as well — while the Apple Watch has improved, it’s not pinpoint-accurate and you should take indoor running metrics as a generally accurate guideline, giving or taking a couple of hundred meters. For most exercisers, that will be enough.
