You’re Wearing Your Garmin Wrong: How to Wear Your Smartwatch for Accurate Heart Rate Readings
My friend Angie recently bought a Garmin Forerunner 265S, and I insisted that one of the first things she should do was get an external heart rate monitor. From my own and other athletes’ experiences, wrist-worn smartwatches are prone to cadence lock and would often produce unreliable heart rate data during runs and even during bike rides—despite providing totally acceptable numbers while sleeping or sitting.
Below is an example of garbage heart rate readings:
Because of these inconsistencies, I had been using an external armband heart rate monitor for almost all runs over the last couple of years. More recently, I had switched to a chest strap for sprint workouts. Both external heart monitors were relatively inexpensive, ranging from $20 to $40 on Amazon, all while producing great accuracy.
However, Angie rejected the idea even though I recommended it at least a half-dozen times. As a minimalist, she didn’t want to have to put on yet another device while working out.
“Haha, I’m stubborn,” she said.
But she soon realized how important accurate heart rate data was. It influences Garmin’s VO₂ max estimations, acute exercise loads, Training load, Training Readiness, Daily Suggested Workouts, and recovery recommendations. She was particularly perplexed when her Garmin insisted she take 96 hours of rest and wondered why.
We checked her acute and training loads, and sure enough, they were absurdly high—even though none of her workouts exceeded an hour. The watch incorrectly thought she had been doing an outrageous amount of anaerobic work. She also noticed that her Garmin believed her daily F45 workouts were pushing her into Zones 4 and 5, whereas she was only in Zones 1 and 2 based on perceived effort.
Since she was adamant about not wearing an external heart monitor, I set out to find a way she could wear her watch while still getting accurate heart rate readings.
How to Wear a Garmin for Better Heart Rate Accuracy
On Reddit, some users suggested that wearing the watch on the underside (palm side) of the wrist led to more accurate readings. Others reported good results wearing it on the top side of the arm, but two finger widths away from the wrist bone.
I tested both positions extensively and came to the following conclusions.
1. Wearing the Watch on the Underside of the Wrist
Out of the two options, this is my favorite for running. I do the “African long-distance arm swing” when running, where my arms pass in front of my chest, punching the centerline. Wearing the watch on the underside of the wrist makes it easier to read since I don’t have to rotate my wrist. It also feels more secure because the watch isn’t on a tapered part of my arm so it can’t slide, which can be an issue with the other recommended watch position if the band isn’t tight enough.
I’ve worn the watch in this position many times now and have never experienced cadence lock.
I tested this position during many base runs and compared the heart rate readings to those from my armband heart rate monitor. Take this Zone 2 base run, for example:
The heart rate readings were virtually identical throughout the entire run. Even the average and maximum heart rates (134 and 142 beats per minute, respectively) were exactly the same.
Even during sprints, the watch performed surprisingly well. When compared against my chest heart rate monitor, it showed some lag and missed a few peaks but far less than I expected.
Where the above chart is circled in red, the Garmin missed the HR peaks by only 2-3 BPM. That’s too trivial to meaningfully affect your statistics.
Unfortunately, my chest heart rate monitor stopped recording after 27 minutes for some unknown reason. However, based on the rest of the chart, the Garmin data looked very reasonable. The only major discrepancy occurred during the 11th sprint, where the watch likely underestimated a peak. (That happened when it started raining hard, which may or may not be a coincidence.)
The watch also did well in a 4X [8:00 threshold + 2:00 recovery] interval workout:
Initially, it read low for the first three minutes, but I tightened the band by one notch, and the readings became accurate for the rest of the run. So far, this was the only workout I’ve done with the watch underneath the wrist where the watch was significantly off. At least it wasn’t due to cadence lock! (For the record, once in a while the external armband heart rate monitor has produced bad readings and has needed repositioning, too.)
2. Wearing the Watch Two Finger Widths Away from the Wrist Bone
While riding my road bike, wearing the watch on the underside of my wrist is not ideal. This is because my wrist often rests on the top of the handlebars, especially when I’m riding in the aero hoods position:
Thankfully, wearing the watch on the top of my arm—two finger widths away from the wrist bone—provided excellent heart rate readings as well. In this position, there is more flesh surrounding the sensor, and it sits well away from the wrist bone, which can sometimes lift the watch and cause poor readings.
Incidentally, this is actually what Garmin recommended in the owner’s manuals for their smart watches years ago—at least in their depictions:
They should have, however, used a lot more precise English in their written instructions. Instead, they wrote,
Wear the device above your wrist bone. NOTE: The device should be snug but comfortable. For more accurate heart rate readings, the device should not move while running or exercising.
I have a few issues with what they wrote. First, above can easily be interpreted as on top of your wrist bone, which is not a good position. Second, if you raise your arm above your head, the watch is now below your wrist bone! Third, they did not indicate how far from the wrist bone it should be. In my experience, it should be at least an inch away and not, say, one millimeter.
At least their image is good. Below is a comparison of heart rate data from my Garmin, worn in this position, versus my external armband heart rate monitor during a recovery ride:
The external armband heart rate monitor was broadcasting to my bike computer, so I could easily compare both devices in real time. 98% of the time, their readings were within 2 BPM of each other.
On rare occasions, the Garmin lagged by as much as 16 BPM, but only for a few seconds. In the final analysis, this discrepancy was negligible. The average and max heart rate readings were:
- Garmin Epix Pro Gen 2: 106 BPM (avg), 131 BPM (max)
- XOSS BBP armband HR monitor: 104 BPM (avg), 132 BPM (max)
I also tested this position while running. While I prefer wearing the watch on the underside of my wrist for running—since I don’t have to rotate my wrist to check it—this position worked just as well.
Below is heart rate data from a Zone 1 recovery run on a treadmill. I didn’t wear an external heart rate monitor for comparison, but the graph looks exactly as expected for an easy run. There were no telltale signs of cadence lock. My cadence exceeded 180 steps per minute, yet the heart rate readings never came close to 180 BPM.
Other Considerations
Band Tightness: The watch should be snug enough that when you move it, the skin underneath moves with it. However, it shouldn’t be so tight that it cuts off circulation.
Band Type: Some people claim that nylon Velcro bands provide better heart rate readings due to better fit. However, in my experience, Garmin’s stock silicone bands work great. They’re comfortable, don’t absorb moisture, and are stretchy enough to accommodate forearm contractions and hand movements.
Cold Weather Performance: I haven’t tested the Garmin’s built-in HR sensor in extremely cold conditions yet, since Galicia never gets too cold. Optical heart rate sensors can struggle in frigid weather due to vasoconstriction. However, armband monitors can also have issues since they use optical sensors too. In really cold conditions—like a snowy winter day in Colorado—I would probably opt for my chest strap.
Garmin Heart Rate Module: The Garmin Epix Pro Gen 2 watch that I did all of the testing with uses Garmin’s V5 Elevate sensor. But users of the popular Garmin Forerunner 265 that uses Garmin’s V4 Elevate sensor have reported good results with the two recommended watch positions in this article.
For the record, the Epix Pro Gen 2 seemed just as prone to cadence lock as my former Garmin Forerunner 645 Music watch that used the V3 Elevate sensor. Garmin claims the V5 Elevate is their most accurate sensor module yet, but I am guessing that is only due to responsiveness (less lag) and not because it succumbed to cadence lock any less than their older sensors.
Conclusion
If you wear your Garmin in one of the two positions suggested above, its optical heart rate monitor is reliable and accurate. You do not need an external heart rate monitor. While there’s a slight lag and occasional missed peaks during rapid heart rate changes (such as during sprints), the accuracy is generally very good.
Personally, I will continue using my chest strap for sprints simply because I already have one and it is gratifying to see the really sharp HR peaks after completing a hard workout, but I don’t consider it necessary. It may be essential for really cold runs when optical heart rate sensors can struggle, but that remains to be seen. If I find that to be the case, I will update this article.
For those who don’t already have an external heart rate monitor, I no longer recommend getting one notwithstanding another compelling reason (e.g., you have tattoos or super hairy arms). Even for broadcasting heart rate to a bike computer, newer Garmin models allow you to do so directly with a few button presses in either the Run Settings or settings for Heart Rate, so you don’t need an external HR monitor for that either.
I will no longer use my armband heart rate monitor for anything except for testing purposes. It is nice not to have to put on, charge, and deal with the occasional bad connection of an additional device. It will also be great to be able to pack one less gadget while traveling.
Thanks to Angie for being stubborn! For the record, she later reported that wearing her Garmin Forerunner 265S on the underside of her wrist “fixed” her heart rate readings as well.