Since our first Fitbit investigation resonated among many of our readers and watchers, we decided to make a part 2. While the first article dealt with Fitbit, its controversial (and deceitful) past, and new features like heart rate variability (HRV). Here we will have a look at Fitbit Stress Management, Fitbit EDA and their new scoring system.

Ever since Google purchased the company, Fitbit’s performance has gone downhill. No new products, dramatic reduction in their marketing budget and no R&D. We thought they should be making new products, with new biomarkers yearly. Not only did they take this advice, but they also completely stole ideas from products like the AIO Smart Sleeve and Whoop.


This isn’t just some outlandish accusation. It is sad to say that this type of thing happens too often in our field. Large companies compete using money, whereas smaller companies compete using innovation. The big boys like Apple, Amazon and Fitbit have the power to copy ideas from smaller wearable companies. 

This was evident from the WHOOP scandal. Amazon had come out with a new health bracelet called the Halo Band. The design looked strikingly similar to that of the WHOOP Bracelet. In fact, WHOOP CEO, Will Ahmed, went to Twitter to expose Amazon. He said the two parties met years ago to form a collaboration on a new wearable product. However, the two parted ways and amazon came out with a product that looked like a copy of WHOOP.

With all of that in mind, let’s take a deep dive into all things Fitbit stress management. We’ll focus on the company’s two newer developments: Daily Readiness Score and Fitbit EDA / stress management.


The new feature that can be used with the Fitbit Sense, Versa 2 and 3 is called the Daily Readiness Score. The score is calculated by taking into account 3 biomarkers from the device: 1) Sleep, 2) activity and 3) heart rate variability (HRV).  The idea is to make sure your sleep is optimized and that your HRV isn’t too low. 


We’re not going to spend too much time explaining HRV here, we made an entire article for that. However, HRV is the holy grail. The most important and amazing biomarker that will transform your health. It’s essentially your body’s check engine light. HRV and stress are inextricably linked. As companies and society begins to understand its importance, we see it being used more and more. 

Now here’s a detailed description, from Fitbit, about how the daily readiness score works:

“A high score means you’re ready for a higher-intensity workout. A low score means your body is fatigued from a tough workout, poor sleep, stress or strain on the body—or a combination of these factors. Prioritize rest & recovery on low score days. See what to expect on high- and low-score days below.”

Fitbit inc.

Now here is an excerpt from our own blog post in 2019:


The language is similar. The use of the word “strain” in the context of HRV was pioneered (on the consumer market) by WHOOP. Obviously, they don’t have ownership to the word but even our company knew about it. For this reason, we came up with our own terminology.

For years, we have stated that typical sleep analysis that you see in products today is simply not enough. It doesn’t provide the full picture. You need HRV data, SPO2, etc, to complete the picture. Well, Fitbit listened.


This is probably the most important point to take into consideration. There’s no such thing as an HRV sensor. Heart rate variability depends on other sensors to acquire data. In reality it either uses an optical sensor or an electrocardiogram (ECG / EKG) to create an HRV value.


Most Fitbit devices are equipped with a PPG (photoplethysmography) sensor. If you have one, you’ll notice shining green and red lights flashing when you turn it on. That’s the PPG. To measure heart rate, this sensor is ok. But for HRV it’s less than optimal. Most studies that rely on HRV will only operate by using an ECG / EKG to extract heart rate variability. 

The difference is in the sampling rate. This refers to how often the device communicates data points to the app. With optical it’s maximum 50 samples per second, whereas ECG is minimum 350 samples per second. It’s quite a difference.


Another important point. The company has seen its fair share of legal battles. They have been sued many times before for false data, over reporting steps, inaccurate BPM reading, and so on.

They manipulate sensors in order to provide a better picture for the user. While it might look nice, it’s not always accurate and can be misleading to customers.


In a few years, you won’t be able to mention the word stress without immediately mentioning HRV. HRV and stress go hand in hand. In the past, “stress” was always thought of some excuse for lazy people. But it’s real and heart rate variability is the sure way to monitor it.


A feature that is only available on the Fitbit Sense is the EDA Score. This is the company’s way to gauge stress levels, readiness and tiredeness. They are trying to show you whether your body is in ‘fight’ or ‘flight’ mode. This is done with the help of an EDA sensor, a technology that has been around for quite some time.


Electrodermal activity was initially known as Galvanic Skin Response (GSR). In the simplest of terms, EDA is a sweat sensor. And theory has it that sweat = stress. In more complex terms, it refers to skin conductivity. When a person sweats, it affects how conductive your skin is. In medical practice, this is measure by placing 2 electrodes on your body, connect the two points with a wire and test conductivity between the two points.

To dig even deeper, sweating is a stress response that can be traced to the autonomic nervous system. This is the part of your nervous system that deals with involuntary actions; things that your body does that you can’t control. This includes digestion, sweat, kidney function, etc. The autonomic nervous system can then be further broken down into sympathetic nervous system, and parasympathetic nervous system. Otherwise known as “fight-or-flight”.


Sweating and other stress responses are associated with the sympathetic nervous system. Preferably, you want to be in the parasympathetic mode all the time. This means your body is relaxed and there is little stress internally. But it’s impossible. Daily tasks like exercise and digestion will put initiate a sympathetic response.


EDA is a bit flawed when it comes to a consumer product. If you are nervous, under pressure and you begin to sweat, you don’t really need a sensor to tell you that. It’s kind of obvious to you. On the other hand, this is a good application for businesses monitoring employee health, alertness and stress because they probably won’t tell employers when they are under stress. There’s even a study that monitored truck drivers and their alertness and tiredeness with this sensor. So, there it makes sense.

According to Fitbit, EDA shows you whether your body is showing fight or flight responses and exertion balance. The latter is supposed to help you recover and to not over train or over work. There’s also a portion of the app where you input how you are feeling. You do this by selecting emojis. This idea was pioneered by UPMOOD, a Hong Kong based company. A potential lawsuit is imminent.

Finally, they have paired the device with a content section that includes helpful articles and mindfulness practices they hope will help in stress reduction. Trying to bridge the hardware technology and create helpful content similar to the Calm App and Headspace.


I don’t need to check the temperature of a burning house to figure out if there’s a fire. That’s kind of what an EDA sensor is. On the other hand, if I had a sensor in the house that sent a notification to my smartphone about a gas leak, that would be helpful. That example is similar to heart rate variability.

There’s no debate regarding which of the two is better; electrodermal activity or heart rate variability. HRV is clearly superior. Especially if you are using ECG to do so. HRV can pre detect potentially fatal issues. Using HRV and seeing a continuous drop means you can actually do something to prevent a bad outcome. It keeps you in touch with your health. It helps you visualize how your daily routine is affecting your health, heart and other organs in your body.


It’s good to see Fitbit dive into the stress and wellness space. This brings awareness to the cause and other startup companies that are doing amazing things in the space. It’s amazing to see the big companies preaching the importance of mental health and the technology that goes with it. 

No matter what we think of Fitbit, they are still the godfather of the wearable tech industry. The early days led to fanatics that continue to buy their products today. They are great at marketing, and making people feel good. If people feel good by using their products, not much more can be said. 

However, this doesn’t mean we can’t explore new products. Companies like Komodo Technologies, WHOOP, and Oura who have pioneered the new field of heart rate variability monitors. A field which is welcoming companies like Apple and Fitbit because they see the importance of HRV. Sure, it’s upsetting when we see these companies stealing our ideas. But on the other hand, that tells us we are doing something right.

If you are planning to get a Fitbit for the stress feature, the EDA and the readiness score, just be cautious. We simply wanted to outline in detail what the technology means, and break down the industry jargon. We want you to know how it works, where the data is coming from and everything in between. If you are looking for advanced analytics, there are a dozen companies that do a much better job. Products like Polar, AIO Smart Sleeve, and Muse.

Thanks for stopping by!

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