Sunday Runday
In this weekly column, Android Central Wearables Editor Michael Hicks talks about the world of running and health-related wearables, apps and fitness technology in your quest to be faster and fitter. .
Athletes often choose a chest strap, armband or fitness watch to measure heart rate to judge health and effort. However, a relatively specific (and strange) option is to use wireless headphones with heart rate monitoring. I recently heard about this technology and immediately decided to test whether the headphones’ heart rate accuracy is good enough for serious athletes.
When I read about the Sennheiser Momentum Sport, which sends HR data to the Polar Flow app, I wondered if Polar H10 users would want or trust a headphone solution or if this is aimed at more casual fans.
Some Athletes Like Standalone LTE Smartwatches for Phone-Free Workout, But I Don’t Know any athlete who would want to train without a watch, especially since they would lose things like GPS, race form data, and a quick-look screen. So instead of replace a fitness watch, maybe these fitness headphones could provide more accurate data.
I decided to try several wireless heart rate headphones, but the more I looked, the more I found unique and discontinued products like the Bose SoundSport Pulse and Jabra Elite Sport. It made me wonder why these brands didn’t bring HR technology to other workout headphones: consumer apathy or unreliable results?
I tested the Sennheiser Momentum Sport and Anker Soundcore Liberty 4 headphones with my favorite Garmin fitness watch and a COROS heart rate monitor on several runs and walks, to judge whether I can trust the headphones for accurate training data.
Headphone Heart Rate Accuracy Test
Anker Soundcore Liberty 4 only makes its workouts available through the “Wellness” page of the companion app. You cannot export your workouts to other fitness apps like Strava or even see your workouts unless the headphones are connected. The basic training results page shows an average HR, a graph, and configured HR zones that I couldn’t edit.
In other words, Anker’s decision to force you to use its app makes the data virtually useless for athletes. Still, I had already run three miles using the Liberty 4, Garmin Forerunner 965, and COROS HRM synced to another COROS watch, so I did my best to interpret the data.
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The COROS HRM determined an average of 147 bpm for my three mile run. My Garmin Forerunner 965 measured 148 bpm; The graph above shows times when it drops more slowly than the cuff when my pace slows or it doesn’t detect small changes in heart rate. It generally matches with few errors, which would be expected from a reliable optical heart rate monitor.
As for the headphones, Anker calculated an average of 149 bpm, which doesn’t seem too inaccurate at first glance. But if we look closely at the heart rate graph, I see that it reaches 167 or 168 bpm during sustained stretches during my run; Neither Garmin nor COROS measured me more than 159 bpm.
There’s also the simple fact that while running with the Soundcore app open, my heart rate seemed to fluctuate much more erratically than either my watch or my HR strap. It may have averaged something close to the correct result, but it didn’t leave me confident. And in the end, the right earbud, which tracks heart rate, drained its battery much faster than the left.
I switched to the Sennheiser Momentum Sport as it exports to the Polar Flow app; This meant I could compare heart rate charts directly and better test the heart rate accuracy of the headphones. To start, I did an impromptu four-mile walk with my headphones and Garmin watch, followed by a five-mile run.
For the hike, Sennheiser trailed Garmin by 1 bpm; Given that the Garmin typically averages about 1 bpm above my arm and chest straps, that’s not a bad result. I noticed some anomalies on the graph where the Sennheiser made my heart rate jump well above my actual exertion level, but overall it tracked my Forerunner data pretty closely.
In comparison, my race results were disappointing:
Things started very well. Sennheiser once again had a couple of high points in the first few miles, but calmed down and followed Garmin closely for the first 3.5 miles. I then decided to pick up the pace, at which point the Momentum Sport couldn’t keep up: they were averaging about 10 bpm lower, sometimes just 5 bpm lower, but often up to 15 bpm lower.
Sennheiser finished with an average of 153 bpm, just two shy of Garmin’s estimate. This is perfectly fine for an everyday athlete looking for data on calories burned, but it’s not accurate enough to make a serious athlete happy.
I decided to do a more proper test. I used the Sennheiser fit test to confirm I had the correct earbud size, put on the COROS band and Garmin watch, and did one more run split into two activities: one at a slow pace and one a hard track workout.
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Imagine my intense frustration upon discovering that the Sennheiser and Polar did not sync properly. For both my short run and track training, the Polar Flow app stopped receiving new information and locked my heart rate at a set point. I didn’t notice because I kept my phone in my pocket while I ran.
You might assume that you should keep the Polar Flow app open, but that wasn’t the case with my previous tests. Also, you can see the track workout above which shows it suddenly started receiving heart rate data near the end, with my phone still in my pocket. In that brief glimpse, it was more of the same: the Sennheiser Momentum Sport was 10 to 20 bpm below my actual heart rate.
Niche for a reason
I started this headphone heart rate accuracy test totally optimistic about how the results would turn out. I had a vague feeling that my ears would provide a reliable window to my heart, in the same way you can take someone’s pulse with your wrist or neck. Instead, I came away disappointed.
I’ve never gotten any results that suggest you should rely on workout headphones as much as a fitness watch; The inaccurate data reminded me more of smart rings, which are accurate under ideal conditions but can struggle with accurate training data and higher heart rates. Additionally, I missed wearing open-back headphones, which feel much more secure and comfortable during runs.
The Sennheiser Momentum Sport also monitors body temperature during workouts, but that was also a disappointment.
I used a pro-grade temperature sensor during track training in March and found that my body reached a mild fever (101ºF / 38.3ºC) with maximum effort. Sennheiser said my body heat never went above 97.8ºF. I suspect that the outside airflow kept my ear canals cooler than the rest of my body and that these headphones would work better for working out in an indoor gym.
A weightlifter who hates wearing watches at the gym could get away with using heart rate headphones and get decent results for an overall calorie burn figure. Otherwise, I simply don’t see the need for this technology, at least until a company can achieve more consistent data.
