Health Wearable Review: Lief Continuous HRV Monitor by Lief Therapeutics

From the very first day I had Lief on, it changed my life completely providing insights previously unavailable. This may sound a little dramatic, but for me, who had no clue for why my HRV is routinely so lousy, continuous HRV data finally pinpointed which types of activities and/or life choices are hurting my HRV score.

But how is it like to use Lief? It comes with a wearable ECG hardware and an app that shows your HRV data. Are they easy to use? Which features do the app offer? Do I wish for any improvements? This article covers those and many other questions. If you are also interested in my personal HRV discoveries that I found out using Lief, you may find interesting these articles; “Is Standing Workstation Hurting HRV?”, “Try This One Thing to Improve Your HRV Instantly”.   

The Lief Wearable

Lief is a clinical-level ECG wearable, attached to the chest area with two adhesive electrode patches. I can usually reuse the same patches well over 3 weeks while wearing them every day. If the adhesives are getting weaker, you can wipe them with a wet paper/towel to make them sticky again.

Lief is flexible and adjusts to the body’s dynamic movements. As such, it’s super comfortable, and I often forget that I’m having it on me! It can be worn during sleep, too, and if you choose this option, you can turn off the biofeedback vibration (more about Lief’s biofeedback feature later) while you are asleep. I personally wear Lief during my aware time, because I’m primarily interested in discovering and implementing actionable insights to improve my HRV.

Lief wearable

ECG vs. Optical Sensors

Let us take a closer look at sensors, one of the key components while considering an HRV (or many other types of) wearable. The choice of sensors is important, because it affects the wearable’s accuracy greatly. When it comes to an accurate heart’s signal measurement, a direct measurement of the heart’s electronical signals with ECG is the clinical golden standard – that’s why you’ll be hooked to an ECG machine, when you go through a heart checkup at the doctor’s office. For a wearable, though, many manufacturers choose optical sensors instead, for a cost or other reason.

Optical sensors flash LEDs through the skin and detect blood flow. The resulting reflection of the light is converted into a heart rate via the wearable’s algorithm, making it more prone to inaccuracy. Moreover, there are two types of LEDs used for optical sensors: red and green. Optical sensors that emit green light can result in even less accurate data especially on a darker skin, because melanin, the skin’s color pigment, is an excellent absorber of the green light.    

In my interview with Rohan, founder & CEO of Lief Therapeutics, he shares fascinating background for why ECG sensors were the best and most natural choice for Lief.

In this Kickstarter page, you can see Lief wearable’s technical spec with a picture of the ECG sensors.

The Lief App

Live HRV tracking

The Lief app shows three variables; heart, HRV and HRV zone in a colored bar form. The HR and HRV are live data i.e. you will be seeing your HR and HRV of this moment. The HRV zone gets updated every 5 minutes, and the color and length of the bar visualize the average zone you were in. Lief customizes the zoned according to your previous data. For example, Restore Zone (the “best HRV zone”) for me at this moment is any HRV values over 19, whereas the same values for other users can be within the Alert or even Tense Zone (the lowest zone).


You can initiate Lief’s biofeedback vibration in three different ways; by choosing the Train option in the app’s menu, by tapping the wearable and having a very low HRV in the Tense Zone that will automatically trigger the vibration. On the app, you will see prompts to exhale and inhale. Lief customizes the durations of the exhalation and inhalation basing it on your breathing data. The vibration is noise-free and discrete – only you will know that it’s on.


Lief offers basic statistical insights including average HRV over a given period. Under app’s menu “Progress”, you can display the average HRV, HRV range, Downtime Dosing, and Wear Time during a week, month or a customized period. To move to the previous/next period, you need to re-choose the desired period rather than just swipe the screen to the left/right.     

Lief app displays your actual HRV only real-time; for any previous period before now, you can see only the average HRV under a 5-minutes period as the HRV zone bar and/or average HRV during a given period (eg. a week) in Progress. Since Lief doesn’t include HR in its analytics, it only provides real-time HR data and doesn’t record your past HR for a later view/analysis.   


Considering getting an HRV monitor? 

You may find Lief uniquely valuable if you primarily want to:

  • monitor your real-time HRV while performing your daily activities, including light physical activities (Lief wearable tolerates a light sweating)
  • gain actionable insights about your HRV (i.e. what actions/situations hurt/improve your HRV)
  • get a clinical-level accurate HRV measurements
  • instantly improve your HRV through biofeedback-led deep breathing  

You may find Lief less attuned for your needs, if your primary goals are:

  • to collect detailed data about your HRV and/or HR
  • to gain insights of your HRV trends via statistics
  • to have an “all-in-one” wearable that provide data beyond just HR and HRV (e.g. activity level)

Use code EEVA at checkout to get a 5 % off from your purchase/subscription at Lief!

Use code KENKOHACKS to get 10 % off from your entire order at