Updated: Aug 29
I’ve been training by heart rate for the past 25 years and while I love the ease at which it guides my training zones, there are some major inherent issues - mainly, is my wrist-based heart rate reading accurate? Unfortunately, more often than the answer is no.
In this article, I’ll look at how wrist-based heart rate monitors work, why they have false readings, and what you can do about them.
How Garmin Wrist Heart Rate Monitor Works
Optical heart rate sensors on the back of the watch utilize lights to detect minute variations in blood volume within the capillary layer beneath the outermost skin layer as blood passes through the wrist region.
Though Garmin's wrist heart rate monitor technology is advanced, its intrinsic constraints could lead to imprecise heart rate measurements.
Why Garmin Wrist-Based Sensors May Not Work
Since the sensor attempts to measure blood volume alterations, it may be that blood volume alterations may not be exclusively attributed to heart rate shifts.
Like a balloon, your vascular system's blood volume can be impacted by body movements or large muscle group contractions in the wrist area, posing a challenge to discerning heart rate amidst other signals with greater magnitude and dynamic variability.
A common error is that the sensor is picking up your running cadence due to leg muscle contractions affecting blood circulation in the upper body.
To Ensure The Sensor is Working Properly, Garmin Suggests:
The optical heart rate sensor must maintain continuous contact with your skin.
The watch should be worn snugly, but not excessively tight. It is appropriately snug when the watch and the skin beneath it move together.
If worn too loosely, the watch can move around, creating a gap between the optical heart rate sensor and your skin.
If worn too tightly, the watch can hinder blood flow.
Wear the watch above your wrist bone.
Wearing the watch on the outside of your wrist is recommended.
Silicone bands are optimal for accurate readings with the optical heart rate sensor.
Leather, metal, and nylon bands are less flexible and may be challenging to properly fit on your wrist.
How to Clean Your Garmin Heart Rate Sensor
Optical heart rate monitors are vulnerable to obstructions or blockages hindering the sensor lights. While it is advisable to rinse your device after each workout, additional cleaning may be warranted, notably if you use sunscreen, lotions, or insect repellents.
To cleanse the watch, use a gentle cloth with lukewarm water to wipe the optical heart rate sensor on the back of the watch. After cleaning, rinse the watch to eliminate any residue and then dry it before reattaching it.
Why Chest Strap Heart Rate Monitors Are Better Than Wrist-Based Ones
Chest straps utilize miniature electrode pads to gather the heart's electrical signals. This heart rate measurement technique, known as electrocardiography (ECG), remains unaffected by surrounding light conditions during physical activity and, therefore, delivers a considerably higher level of precision (99% accuracy when compared to a hospital-grade ECG device).
I have good news and bad news. The good news is you can easily fix this. The bad news is it's going to cost you.
If you train by heart rate, invest in a chest strap heart rate monitor. This way, you can be confident you’re training in the correct zones. The one I personally use and recommend is the Garmin HRM-Pro™ Plus.