The older you get, the more attention on the recovery is required. And of course, also a larger amount of training requires careful monitoring of recovery. I wrote earlier that I use HRV measurement (finnish only) as a tool for tracking recovery, which has been extremely valuable for me. Since that article, things have changed a bit and now I have been a user of Emfit’s sleep sensor for more than a year. Emfit takes HRV measurement to the next level, so to speak. I can’t imagine using anything else anymore. The device appeals above all with its ease of use and accuracy.
My goal is to give you a clear picture of what kind of gadget it is. In the article, I go through the operating principle of the device, its features, and my own experiences over the course of a year. Since Emfit offers so much in a small package, in this article I will go through what I think are the most essential things.
What is Emfit?
Emfit QS+Active is a sleep sensor placed under the mattress. Its operation is based on ballistocardiography, which is able to measure heart rate and breathing rate very precisely without contact with the body. Emfit uses its own patented sensor technology, which enables the sensor to be installed even under a thick mattress. The device consists of a power source, a sleep sensor mat, and a unit containing all the intelligence. Data is transferred to Emfit’s own cloud via a wireless network. If the wifi is interrupted for one reason or another, the device stores one night’s data in itself and transfers it to the cloud when the connection is restored. Emfit is a Finnish product.
The best thing about the device is definitely its simplicity. Once installed and put into use, it works completely autonomously and lives a life of its own. It doesn’t need to be paired with the phone app, which is insanely great. The measurement starts automatically when you go to sleep and ends when you get out of bed. The data can be conveniently read from the web page and there is no need to install separate apps.
Features and experiences
Emfit QS provides versatile data. Here I will go through the different data fields that Emfit shows one by one. For the same money, I will also share my own thoughts and experiences about the information in that data field.
Sleep Score, Sleep Time, and Sleep Classes
As the first measure, Emfit calculates the Sleep Score. It is calculated using a certain formula that gives an overview of the quality of your sleep. Emfit writes about it like this:
The calculation formula for the sleep score: (total amount of sleep + length of REM sleep * 0.5 + length of deep sleep * 1.5) – (length of wakefulness / 3600 * 0.5 + number of awakenings / 15) * 8.5 = Sleep score
In simplified terms, this means that the longer you sleep and the more you have REM and the deeper your sleep, the better your sleep score. On the other hand, if you are awake most of the time or wake up often at night, these will reduce your sleep score. The maximum sleep score is 100, which indicates very good sleep quality. In general, values from 80 and up can be interpreted as good sleep quality.
The sleep score rarely gives me any larger-than-life information. In practice, in my case, the number is almost directly proportional to the amount of sleep. The biggest changes come for me if my sleep is less than seven hours or if I had a few portions of alcohol before. As you can see (below picture), the last week has passed with quite long nights of sleep because the corona has slowly recovered. Normally, my amount of sleep is around 8-9 hours at the moment.
Sleep categories are divided into three stages – light sleep, deep sleep, and REM sleep. It is clear that every stage of sleep is necessary for a quality night’s sleep. The green bars (see picture below) describe the optimal range for each stage of sleep. As you can see, according to Emfit, I myself spent longer than normal last night in REM sleep. Of course, these are only indicative times. According to my own experience, they are still significantly more truthful than, for example, the sleep data provided by Garmin’s activity meter (Venu 2). This information goes into the category: ”Nice to know” on my own scale.
HRV – heart rate variability
Then we’ll get to it. Emfit displays heart rate variability (HRV) in several different metrics. The first graph shows HRV values in the evening and in the morning. If the evening value is low, it is a sign that the training has been effective or the body is otherwise stressed. A high value in the morning, on the other hand, indicates efficient recovery. If the evening’s value is higher than the morning’s, it usually means, at least in my case, that the day has been light and there has been no need for actual recovery.
The all-night HRV average is exactly what it promises – an average of all the HRV values measured during the night. This meter is quite useful for me when evaluating the effectiveness of recovery and readiness for a new workout. It often tells more than monitoring values in the evening and morning, although this is also important for me to monitor.
Emfit says this about overall recovery:
Recovery is simply difference between morning and evening RMSSD values. If there has been a lot of physical exertion during the previous day and the evening’s RMSSD has therefore been low, this is usually a positive number. Then it tells you that there has been effective recovery and rest during the night. If the number is negative, it can simply mean that the previous day has been light and you are well recovered by the time you go to bed.
However, this should be evaluated in relation to the previous day’s activities: if the previous day was very light (no stress, no hard training) and if the RMSSD value of the evening was relatively high, it is not reasonable to expect a high total recovery value because there has been no stress load to recover from.
The values of total recovery are highly individual and should be considered in relation to the values of your own baseline, also in comparison to Evening RMSSD values.
The Total Recovery is still a small-scale mystery to me. I haven’t really noticed any clear connection here that I could grasp. In practice, this value means the total area of recovery throughout the night on the HRV RMSSD graph.
You can get HRV data for each day by clicking on the more detailed view. Below is an example of after several rest days. Emfit takes measurement data every three minutes and draws a graph of the heart rate interval variation throughout the night. As you can see, HRV cruises up and down throughout the night.
These are all very handy metrics for tracking recovery. The results are extremely individual and therefore no specific values can be given when things are good or bad. In my opinion, however, Emfit makes monitoring very easy and versatile in this matter.
Autonomous Nervous System balance
The balance of the autonomous nervous system (ANS) is an interesting metric as well. This diagram tells quite precisely which area of the nervous system (sympathetic or parasympathetic) is active. Emfit tells about the soul of this metric as follows:
LF and HF refer to the low and high frequency bands, which are general indices of the frequency level of heart rate variability. LF has a frequency band of 0.04-0.15 Hz, and can be said to represent both the sympathetic and parasympathetic nervous systems. HF has a frequency band of 0.15-0.04 Hz, and it represents the parasympathetic nervous system.
Emfit QS uses normalized units LFn and HFn expressed as a percentage of the sum LF+HF, i.e. LFn=LF/(LF+HF). The diagram shows both LFn and HFn and ideally the reading should stay within the shaded area between 25 and 75.
Deviations from the 25-75 or 75-25 range can be a sign of poor recovery, high or chronic stress, general fatigue or other body dysfunction.
So the optimal range is in green, but in practice, a little lower graph is better. For me, the normal level is right in the middle, but after a few beers, there is a steep rise in the value. Also, stress raises the level noticeably higher. Correspondingly, for example, meditation and relaxation exercises bring the graph down.
Heart rate and Breathing rate
The average heart rate is the average of the whole night. Resting heart rate is measured in three-minute cycles. The lowest average of these cycles throughout the night is the reported resting heart rate for that night. In other words, it’s the lowest three-minute average heart rate throughout the night.
Monitoring your resting heart rate is important and it can tell you about impending over-reaching or stress. For me, specifically, the resting heart rate is a closely monitored value, but the average heart rate also indicates acute stress. Even a few beers in the evening makes my heart rate skyrocket. And oh boy how the graph looks like after heavy drinking….
Another thing that alcohol affects is breathing rate. Be that as it may, I don’t need a sleep sensor for my alcohol use, but the breathing rate tells also a lot about general stress and recovery. As you can see from the pictures, breathing rate and heart rate often go hand in hand.
This is also an interesting metric. Movement metric shows all movement that are not caused by heart beating or breathing. The thinner the sensor is under the mattress, the more sensitive the sensor is for the movements. You can clearly see when you have had a restless night.
It is possible to form trends from all the above-mentioned metrics, from which it is good to look at possible changes in the longer term. Here is an example of 90-day evening-morning HRV:
It’s interesting to follow trends and notice how different things affect the bigger picture. Long-term changes are not easily noticed except by looking at the data. You can adjust the variables of the trends in a very versatile way, which is a very great thing.
I have been a more than satisfied Emfit user. There are many pros and very few cons. The absolute best thing is the ease of use. Even when traveling, the device can be taken along, because connecting the device to a new Wi-Fi network is so painless.
The only criticism Emfit gets from me is that there haven’t been many visible updates, at least during the past year. On the other hand, the gadget already has a fairly comprehensive cavalcade of metrics and features. Another ”criticism” is that, due to the sensor’s sensitivity, it requires a little adjustment in a double bed so that the sleeping partner’s heartbeat does not interfere with use. However, this is a side point as a whole but something that should be taken into account.
This is not a paid advertisement and I am more than happy to give my warm recommendations for using Emfit.
If you got any questions regarding Emfit, HRV or recovery in general, feel free to ask!
How do you track your recovery?