Running with Apple Watch vs Garmin Forerunner 935- Data Comparison

As a follow up to my previous post on HR accuracy of the Apple Watch and to reinforce my belief that it is pretty good on Apple Watch 3 with watchOS 4, here are some recent files for a recent run.

  • On my left hand I wore Apple Watch Series 3 running watchOS 4.0.1 (15R654)
  • On my right hand I wore a Garmin Forerunner 935 running software version 6.00 (d376ccb).  This was paired with a Garmin Tri HR chest belt rather than using the built in optical sensors - this should give more accurate and responsive results since it measure electrical impulses rather than blood flow. 

Data Comparison

After the run I exported the Apple FIT file from Apple Health using the HealthFIT app and the Garmin one using Garmin Connect, then uploaded both the the DC Rainmaker Analyzer.  If you want to see the full analytics you can visit this link:

Heart Rate

From the chart below you can see that following a bit of a shaky start from Apple Watch, it levelled out fairly nicely against the chest band, with a little strange peak at around 30mins (that I am not too concerned about)

Apple Watch Optical vs Garmin 935 with HR Chest Band.  Apple Watch is the blue line, 935 the purple

At around 48 mins I did a few hill repeats to push my HR up a bit higher and see how both watches reacted.  There was a little more variation here with the 935 showing a smoother chart which would be more accurate, and AW struggling to keep up, though personally I wouldn't see this as a problem for my day to day training and logging.  A possible exception may be the AW Max HR of 189 which is too high for my 52 year old body, and could potentially cause other automated systems such as Training Peaks or to get a bit confused about my thresholds.  Still I am happy with this data from Apple Watch.

GPS Track

Looking at the GPS track in overview, again they are much of a muchness.  If you switch to Satellite view and zoom in though, 935 has the edge in a few places with a more accurate track. Nothing I would be too concerned about, but in this case the 935 is slightly better.

Apple Watch is the blue, 935 the purple


This is a tougher one to verify as truly accurate but they both manage to get the overall picture right with the bumps in the right places which is all I need.

AW = Blue, 935 = purple

Average Pace, Distance, Instant Pace and more

This is coming in another post - stay tuned...


Just like in my conclusion here testing HR on a Turbo session, Apple Watch has performed excellently for HR compared to what should be a more accurate Chest Belt, and GPS and Elevation are certainly respectable.  Having said that the 935+chest belt is clearly the winner if you want the most accurate, but given the choice of wearing one watch all the time (for day to day and sport), my preference is the Apple Watch, and the level of accuracy it delivers here is perfectly good enough for the endurance training I do.