Over the past decade, the world of wearable tech for runners has evolved rapidly. What used to be a simple choice between a stopwatch or basic wristwatch has grown into a market packed with GPS-enabled watches, heart rate monitors, cadence sensors, and even power meters.
As a coach, I’ve seen both ends of the spectrum—runners who stick to the basics and others who fully embrace the data-driven approach. While some prefer to run free from distractions, many athletes today rely on technology to track every detail of their training—from pace and distance to heart rate and recovery.
Brands like Garmin, Polar, and Suunto now offer a wide range of advanced devices. And thanks to the rise of wrist-based optical sensors, heart rate tracking has become more convenient and comfortable than ever.
But this brings up an important question: how accurate are wrist-based heart rate monitors—and are they a better choice than chest straps?
In this guide, we’ll break down the pros and cons of both options, so if you’re trying to decide which type of heart rate monitor is right for your training, we will help you make a smart, informed choice.
How Do Wrist-Based Heart Rate Monitors Work?
The technology used to assess your heart rate is different between chest strap and wrist heat rate monitors.
Chest strap heart rate monitors use electrodes to record the electrical conductivity signals of your heart as it contracts (beats) to pump blood.
Much like the electrodes used on an electrocardiogram (ECG), the electrodes of chest HR monitors are sensing the spike on the ECG (called the QRS complex) when the left ventricle contracts and pumps blood out of the heart through the aorta into circulation.
Your heart rate is reported as the number of times this electrical signal is detected per minute because this event occurs once per cardiac cycle, or complete heart beat.
In contrast, wrist-based heart rate monitors use a process known as photoplethysmography (PPG) to detect your heart rate.
Wrist HR monitors are also known as optical heart rate sensors because photoplethysmography uses light (usually green LED lights) and special light-sensitive diodes to measure your heart rate.
The lights flicker hundreds of times per second to determine how many times your heart is beating per minute.
The LED light penetrates your skin and reflects off your blood. The degree to which your blood absorbs or reflects light varies according to whether your heart is contracting (beating) or relaxing in between beats.
When your heart contracts, it pumps blood out to your body, increasing blood flow in your wrist. The greater blood flow in your wrist causes more light to be absorbed, rather than reflected, from the LED light.
When the heart relaxes in between beats, blood is flowing from the body (and wrist back into the chambers of the heart. As the blood volume in the wrist drops during the relaxation of the heart, the skin absorbs less light from the flickering LED.
The light-sending diode registers these two variations in light absorption, integrates the data in the device with an accelerometer (which measures movement), and feeds the data through an algorithm to yield a heart rate value based on the number of times these fluctuations occur per minute.
Just How Accurate Is Your Wrist-Based Heart Rate Monitor?
The main drawback of wrist-based heart rate monitors is that they are typically less accurate1Pasadyn, S. R., Soudan, M., Gillinov, M., Houghtaling, P., Phelan, D., Gillinov, N., Bittel, B., & Desai, M. Y. (2019). Accuracy of commercially available heart rate monitors in athletes: a prospective study. Cardiovascular Diagnosis and Therapy, 9(4), 379–385. https://doi.org/10.21037/cdt.2019.06.05 than chest strap HR monitors.
Research has shown2Reddy, R. K., Pooni, R., Zaharieva, D. P., Senf, B., El Youssef, J., Dassau, E., Doyle Iii, F. J., Clements, M. A., Rickels, M. R., Patton, S. R., Castle, J. R., Riddell, M. C., & Jacobs, P. G. (2018). Accuracy of Wrist-Worn Activity Monitors During Common Daily Physical Activities and Types of Structured Exercise: Evaluation Study. JMIR MHealth and UHealth, 6(12), e10338. https://doi.org/10.2196/10338 that wrist HR monitors are fairly accurate, or accurate “enough,” but the acceptability of any errors may depend on your goals with wearing one and how accurate you need your data to be.
There are several factors that can reduce the accuracy of wrist-based HR monitors, including the following:
#1: Skin Tone
There is some evidence3Bent, B., Goldstein, B. A., Kibbe, W. A., & Dunn, J. P. (2020). Investigating sources of inaccuracy in wearable optical heart rate sensors. Npj Digital Medicine, 3(1). https://doi.org/10.1038/s41746-020-0226-6 to suggest that optical HR monitoring is less accurate on darker skin tones because it’s harder for the LEDs to penetrate darker skin tones to reflect off the blood.
As a result, if you have a darker complexion, a wrist HR monitor may underestimate your heart beat because the light-sensing diodes can miss beats if the light absorption and reflection is poor or the difference between absorption levels is minimal.
#2: Wrist Size
If your wrist is small and bony or your watch face is large, the watch can slide around, which will interfere with the accuracy of data collection.
#3: Band Tightness
If you tighten the watch too much, it compresses the skin. This is problematic because PPG is calibrated for the density of human skin in its resting state, not compressed state, so this again can skew the accuracy of the HR measurement.
The wristband should be tight enough to prevent movement, but not so tight that it chokes your skin or leaves an indentation.
#4: Workout Intensity
The heart rate monitor needs to stay in contact with your skin at all times in order for the optical sensing to measure your heart rate.
Studies have shown4Thomson, E. A., Nuss, K., Comstock, A., Reinwald, S., Blake, S., Pimentel, R. E., Tracy, B. L., & Li, K. (2019). Heart rate measures from the Apple Watch, Fitbit Charge HR 2, and electrocardiogram across different exercise intensities. Journal of Sports Sciences, 37(12), 1411–1419. https://doi.org/10.1080/02640414.2018.1560644 that the accuracy of wrist heart rate monitors decreases with high intensity or increased running speed because there is more movement or “noise” of the device against the skin.
Another study5Chow, H.-W., & Yang, C.-C. (2019). Accuracy of Optical Heart Rate Sensing Technology in Wearable Fitness Trackers for Young and Older Adults (Preprint). JMIR MHealth and UHealth, 8(4). https://doi.org/10.2196/14707 found that wrist heart rate monitors consistently underestimate heart rate during exercises, particularly at higher intensities.
Essentially, the faster you run, the less accurate the HR data becomes. At rest, walking, and slower running, the HR monitor stays in position.
#5: Number and Color of LED Lights
Most optical heart rate monitors use one, two, or three green LED lights. The more lights, the better chance they have at shining light effectively enough to absorb it by the blood.
There is also a general consensus that tri-color or red lights in addition to or instead of just green lights increases accuracy because red light penetrates skin better.
#6: Moisture
Sweat or water while swimming can reduce the accuracy of wrist heart rate monitors by introducing noise and interfering with the light reflection.
#7: Cold Hands
Your wrist-based heart rate monitor is often less accurate in the winter if you have poor circulation in your hands and wrists. If blood flow is reduced, there is less volume coming in and out with each heartbeat, making it harder to detect a change in light reflection.
#8: Activity
Unfortunately, wrist-based HR monitors seem to be less accurate6Etiwy, M., Akhrass, Z., Gillinov, L., Alashi, A., Wang, R., Blackburn, G., Gillinov, S. M., Phelan, D., Gillinov, A. M., Houghtaling, P. L., Javadikasgari, H., & Desai, M. Y. (2019). Accuracy of wearable heart rate monitors in cardiac rehabilitation. Cardiovascular Diagnosis and Therapy, 9(3), 262–271. https://doi.org/10.21037/cdt.2019.04.08 running than cycling.
While there are factors that can reduce the accuracy of wrist HR monitors, they are generally considered to be accurate enough for most healthy runners. Errors are usually arounds 5% or 3 beats per minute.
There are plenty of options, including Apple watches, Garmin, Polar, Suunto, Fitbit, and even Samsung, all of which will track your heart rate and come with various features.
The Benefits of Wrist-Based Heart Rate Monitors
Most runners find wrist-based heart rate monitors far less cumbersome than chest straps, especially now that many GPS running watches integrate heart rate monitoring directly into a single smartwatch.
That means no extra gear—just one device that tracks your pace, distance, and heart rate in real time.
Another major benefit is that wrist-based monitors can be worn all day and night.
This allows you to collect continuous data, such as resting heart rate, heart rate variability, and sleep quality—valuable metrics for assessing recovery and overall health. These insights can help guide your training by showing when you’re well-recovered and ready to push, or when you might need more rest.
Lastly, the convenience and comfort of wrist-based monitors make them a great option for runners who prioritize consistency and simplicity. You’re more likely to track your training consistently when your gear is seamless and comfortable to wear.
The Downsides of Chest Strap Heart Rate Monitors: Accurate, But Not Always Practical
Chest strap heart rate monitors used to be the only option available to runners who wanted to measure their heart rate while running. These devices are quite accurate and are often considered the gold standard to measure heart rate, but several drawbacks exist.
Chest straps:
#1: Can Be Uncomfortable
Heart rate monitors that use a chest strap can be quite uncomfortable when you are running or working out. The chest strap has to be tight enough to keep the electrodes stationary against your skin, which can restrict breathing, or at least create the sensation of restricted breathing.
#2: Can Be Tricky to Position Properly
The accuracy of heart rate data from a chest strap HRM is also highly dependent on proper positioning. The electrodes should ideally sit just below the nipple line.
For some runners, they can be tricky to secure properly, and unfortunately, the farther away the HR monitor gets from your heart, the weaker the electrical signal, which can lead to a loss of connection and an absence of your heart rate data.
Women who wear a sports bra while running often complain that chest strap heart rate monitors interfere with the positioning of the sports bra, as the chest strap and the lower elastic band or underwires of the sports bra often compete for the same “real estate” or skin area of the chest.
Although there are some sports bras for runners specifically designed with a sleeve in the band for a heart rate monitor, they are expensive and may otherwise not meet the needs or likings of the runner.
#3: Chest Strap HR Monitors Can Slip
Heart rate monitors that rely on a chest strap are prone to sliding down or twisting around laterally from their initial placement while running or doing any cardio, especially if it’s high intensity.
This is not only a frustrating nuisance, as you have to keep readjusting the strap or shimmying it back into position, but it also interferes with the consistency and overall percentage of heart rate data captured during the run.
In other words, if the heart rate monitor falls down or slips out of place, the electrodes will lose contact with your skin in their proper placement positions and won’t be able to capture your heart rate data accurately.
#4: Require a Wrist-Worn Device to See Your Data
Another drawback of heart rate monitors with a chest strap is that you have to wear a wrist unit of some sort simultaneously if you want to be able to see your heart rate metrics in real-time through ANT or Bluetooth.
Therefore, you are encumbered with yet another device, and if you have a different running watch, you’ll have to wear units on each wrist.
#5: HR Monitors Corrode
Finally, the snaps that hold the electrodes in place on chest heart rate monitors are prone to corrosion from sweat, which starts to render them faulty, as the corrosion interferes with the accurate and consistent electrical conduction that detects your heart rate.
Corrosion of the snaps frequently leads to the premature breakdown of the HR monitor.
Which Heart Rate Monitor Is Right for You?
As wearable technology continues to evolve, runners now have more ways than ever to track and optimize their training.
Wrist-based heart rate monitors offer a convenient, comfortable, and user-friendly option that integrates seamlessly with GPS watches and provides valuable all-day data. While they may not always match the precision of chest straps—especially during high-intensity workouts or for runners with certain physiological traits—they’re generally accurate enough for most recreational athletes.
On the other hand, chest strap monitors remain the gold standard for accuracy but come with notable downsides, including discomfort, maintenance issues, and added gear requirements.
Ultimately, the best heart rate monitor for you depends on your training goals, your tolerance for gear, and how much precision you truly need.
If you value simplicity and daily tracking, a wrist-based monitor may be the perfect fit. If pinpoint accuracy is your top priority—especially for interval training or heart rate zone training—a chest strap might still be worth the hassle.
If you are looking to focus on heart rate training, check out our next guide to calculate your zones:
I think the arm band heart rate sensors offer the best of both worlds. more accurate than wrist based, and more comfortable than chest straps.