Heart Rate: Wrist v Chest Monitors

My empirical evidence of Heart Rate does not match that expounded by Internet Experts and Fitness Influencers. To try to figure out what was going on I bought a HR Chest strap and compared it to my Garmin Forerunner 245 wrist based Heart Rate measurements.

Electrical (electrocardiography): Your heart generates a small electrical current with every heartbeat. Heart rate monitors with electrical detection capabilities can detect and track that current.
Optical (photoplethysmography): These devices use infrared light to see the expansion of your arteries as your heart pumps blood through them. When that light refracts (or reflects) off your flowing blood, another sensor in the wearable captures that information. That data can then be processed, along with motion information detected by the device's accelerometer, with algorithms to produce understandable pulse readings.

Here is a summary of my findings for the wrist based Garmin 245:

At rest the wrist based Garmin 245 is fairly accurate
Doing any kind of HIIT and the wrist based Garmin 245 lags by a number of seconds and misses peaks.
Doing any kind of Weight Training and the wrist based Garmin 245 lags by a number of seconds and misses peaks.
When brisk walking the wrist based Garmin 245 under reads consistently
When running the wrist based Garmin 245 is surprisingly accurate

Heart Rate Zones

Garmin defines the Heart Rate Zones as:

Zone 1 (Warm Up) - Relaxed, easy pace, rhythmic breathing.
Zone 2 (Easy) - Comfortable pace, slightly deeper breathing, conversation possible.
Zone 3 (Aerobic) - Moderate pace, more difficult to hold conversation.
Zone 4 (Threshold) - Fast pace and a bit uncomfortable, breathing forceful.
Zone 5 (Maximum) - Sprinting pace, unsustainable for long period of time, labored breathing.

After some testing I reckon my Max Heart Rate is 185:

HIIT Bike

First up was a half hour Bike HIIT session. One minute rounds of all out effort with increasing rest periods.

The wrist based Garmin 245 HR monitor lags by a number of seconds and misses peaks. The Chest Strap HR monitor felt spot on. But even this was well short of my Max HR. Reading around on the Internet apparently Max HR for cycling is lower in all untrained cyclists. This would then seem to suggest cycling is not great for HIIT work since your HR never gets near maximum. Short sprint running would seem to be much better.

HR ZONES

Weights Session

Next up was a weights session focusing on upper body compund exercises.

The wrist based Garmin 245 HR monitor lags by a number of seconds and misses peaks, especially at the beginning of the session. The Chest Strap HR monitor was spot on, recording high heart rates on difficult sets right at the start of the session. The change between sets and rest periods was also clear to see on the Chest Strap HR monitor.

HR ZONES

But according to this a tough session in the gym has no anaerobic value!

Brisk Walk

Next up was a brisk walk. One of the main reasons I bought a Chest Strap was because the Garmin Wrist Based HR monitor seemed to read quite low on a brisk walk, barely getting me into Zone 2.

KM	WALK TIME	PACE MINS/KM	SPEED KM/H
6	0:53:42	8:57	6.70

At the start of the walk the wrist based Garmin 245 HR monitor was reporting a lower heart rate. The Chest Strap HR monitor was fairly consistent.

HR ZONES

So its true, at a brisk walk at quite a demanding pace my Heart Rate remains quite low and struggles to get into Zone 2. So I must be pretty fit.

Run

Next up was a run. One of the main reasons I bought a Chest Strap was because the Garmin Wrist Based HR monitor seemed to read quite high on a run, putting me into Zone 4, and even Zone 5 for most of the run.

KM	RUN TIME	PACE MINS/KM	SPEED KM/H
6	0:35:18	5:53	10.20

This one was a surprise, the Chest Strap HR monitor confirmed that as soon as I start to run my Heart Rate skyrockets. The Garmin 245 HR monitor was acutally pretty accurate for a run. In fact the Chest Strap HR monitor read a little bit higher!

HR ZONES

So its true even for a run, not even a sprint my Heart Rate skyrockets, and stays high. So I must be pretty unfit.

Conclusion

The Chest Strap HR monitor performed better than the Wrist Based HR monitor, especially when Heart Rate changed quickly.

Now I have accurate Heart Rate readings I am still a bit puzzled. The last 15 minutes of the 6km run were in Zone 5. This is supposed to be impossible. So maybe my Max heart Rate is even higher than the 185, which is very high for someone aged 54. This requires more investigation.