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Research Update

7/27/2021

 
​Blog post by Marco Altini

​Below is an update of our research on the relationship between deep breathing and heart rate variability (HRV).

It's been one year since HRV4Training launched HRV4Biofeedback, making it easier and more affordable to practice deep breathing at your resonant frequency

Interestingly, we found that low HRV can be improved, at least acutely, with deep breathing (any dose might do)
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The previous image shows how people approaching this technique improve their session HRV. Below we also look at dose-response

For some people, any dose will do, but a higher dose seems beneficial in general

​The follow-up analysis shows what drives these differences:
​

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In particular, it seems that only a high dose will provide benefits for people with already high HRV, while incremental benefits are shown for people with lower HRV

​Bottom line: according to this data, if your HRV is low, it can most likely improve (acutely) with any dose of deep breathing
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These changes won't necessarily also improve your baseline HRV, but they might impact positively self-regulation during stressful situations, as well as bring other benefits, which I have recently discussed in this podcast.

Stay tuned for updates

Biofeedback Podcast

6/25/2021

 
Blog post by Marco Altini

I had a nice chat with Michael @ x3training about heart rate variability (HRV) biofeedback 

I hope you’ll find it useful 

Episode link here
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Long term effects of deep breathing on Heart Rate Variability

3/28/2021

 
​Blog post by Marco Altini
In this post, I look at the long-term effects of deep breathing on heart rate variability (HRV) as measured during deep breathing practice
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While there is plenty of data and published literature on the acute effect of deep breathing on HRV (basically the difference between resting conditions and practice), we know much less about long-term effects. Looking at this data might help us better understand the relationship between deep breathing and long-term physiological changes (if any!)

Enjoy the read
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New in the app: select different inhale / exhale ratios for your sessions

3/25/2021

 
Blog post by Marco Altini
With the next update of HRV4Biofeedback, we are bringing to the app one of the most frequently requested features: the possibility to select other inhale to exhale ratios, apart from the standard 50 / 50

The update will be available in a few days and will provide three options:
  • 50 / 50: inhale and exhale are of the same duration. This is the option currently available in the app
  • 40 / 60: inhale is 40%  of the cycle, therefore exhale is a bit longer
  • 1 / 2: inhale is half the exhale period

​In all cases, the base breathing frequency will be the one you have configured manually or determined via the resonant frequency test. This base frequency will be modulated according to your selection, to allow you to use different ratios

Enjoy
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Spot check measurements ADDED IN HRV4BIOFEEDBACK

2/5/2021

 
Blog post by Marco Altini

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We have just added spot check measurements to HRV4Biofeedback, you can see a preview below

When starting a new recording, you will be able to choose between a biofeedback session or a spot check measurement. This way you can for example measure before or after a session (without deep breathing), to assess any potential changes

Spot checks will be 60 seconds long, report signal quality, heart rate and HRV
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30 days of Heart Rate Variability (HRV) Biofeedback

1/30/2021

 
Blog post by Marco Altini

​In my latest blog post, I go over the basics of heart rate variability (HRV) biofeedback and show changes in baseline physiology (resting HR, HRV) potentially linked to practicing deep breathing at resonant frequency consistently for the past month

Learn more, here 

Get breathing!
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Real time panel showing cumulative score, average heart rate and hrv

1/29/2021

 
Blog post by Marco Altini

We have added a real time panel to the app, showing the cumulative biofeedback score (which is based on the session duration as well as the breathing frequency), the average heart rate and HRV (rMSSD) of the session

In order to display the new panel, you need to select it in Settings. The data will be updated every minute during the session
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Current Streak added in the app

1/29/2021

 
Blog post by Marco Altini

​
Another small update for HRV4Biofeedback, we have added the current streak, see below
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Power spectrum of your biofeedback session in the app

1/21/2021

 
​Blog post by Marco Altini
We have added the power spectrum of your biofeedback session directly in the app. You can find it in the detailed view of the session, that you can access from the History menu

Normally, you should see the highest peak in the low frequencies, very close to the breathing rate used for your session. You can see here below an example of a session where the power spectrum peak is at about 0.09 Hz, which then the app translates into a breathing rate of 5.3 breaths / minute
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Here is an example of a session without deep breathing, just to showcase how a resting breathing rate of about 10 breaths / minute is picked up in this case:
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Enjoy the new feature!

Added integration with the Health app

11/18/2020

 
Blog post by Marco Altini

​We have added integration with the Health app in the next version of HRV4Biofeedback, which will allow you to write Mindful minutes, heart rate and HRV (SDNN in this case) to the Health app

Thank you for your feedback. Enjoy!
​
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Added rMSSD to the latest version of HRV4Biofeedback

10/28/2020

 
Blog post by Marco Altini

​Quite a few of you have asked for the HRV (rMSSD) of the session to be displayed in the app. With the latest update, you will be able to find it in the detailed session view (under History) as well as under Summaries and Correlations

Enjoy
​
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Expected physiological, psychological and performance outcomes FOLLOWING BIOFEEDBACK INTERVENTIONS

8/24/2020

 
If you are new to HRV Biofeedback, start from part one to learn more about the foundations or part two to learn more about the important metrics to keep track of both during and outside of HRV Biofeedback sessions. In part three, you can learn more about the most common protocols

In this last part of our introductory series on HRV Biofeedback, we will provide an overview of the main outcomes of HRV Biofeedback interventions, in terms of performance changes as well as physiological or psychological changes. We will first report on early explorations, then move towards higher-quality studies and finally cover recent attempts to investigate HRV Biofeedback interventions in more applied and practical settings

​The issue with performance measures

Before we start, I believe there is an important point to cover, concerning performance measures

In elite sport settings, performance is often the outcome of interest. However, in many sports (e.g. in teams settings), performance cannot be unambiguously measured (Cannon-Bowers and Salas, 1997; Richard et al., 1999; Wiseman et al., 2014), and is often estimated using different approaches

For example, in many situations, athletic performance is measured during isolated tasks (e.g. sprinting ability), which might have low fidelity with respect to the complexity of an actual game. Even when sport-specific tests are used (e.g. a passing test in soccer), it is difficult to extrapolate test results to in-game performance, as often shown by research on talent identification (Den Hartigh et al., 2018; Bergkamp et al., 2019). For these reasons, focusing only on studies that clearly report changes in performance can be limiting. On the other hand, it follows from the previous considerations on HRV Biofeedback (see parts 1–3 of this guide) that physiological and psychological parameters might be mediating the relation between HRV Biofeedback and performance

For example, HRV Biofeedback could increase parasympathetic activity at rest or improve emotional self-regulation during high anxiety tasks (Lehrer et al., 2003, Deschodt-Arsac et al., 2018), which might be beneficial for performance, as further discussed in the next sections. Hence, my goal here is to provide an overview of the effects resulting from the implementation of HRV Biofeedback methods in athletes. In particular, while it makes a lot of sense to first investigate sport-specific changes in athletic performance measures, I will also look at physiological and psychological changes that have been documented in the literature and can mediate athletic performance

In other words, in this post, I aim at answering the following questions: what is the effect of HRVB on athletic performance? How do physiological and psychological measures change following HRVB interventions in athletes?

A summary of the studies and outcomes can be found in the table below, while a thorough analysis of the studies organized by type of outcome (performance, physiological or psychological), is provided in the second part of this blog post

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Read More

Resonant frequency analysis in HRV4Biofeedback Pro

6/3/2020

 
HRV Biofeedback requires to breathe at low frequencies (deep breathing), which stimulates parasympathetic activity. Experimental studies have found the highest amplitudes in instantaneous heart rate oscillations when breathing at approximately 0.1 Hz. This means 6 breaths per minute and is the default in the app

However, the frequency at which amplitude is maximal for a person can be slightly different.  This is what is called the resonant frequency and can vary by up to 2 breath/minute between people


Your resonant frequency can be established with a protocol that consists of breathing at different frequencies for a few minutes until the frequency that elicits the maximal amplitude is found

In our Pro platform, you can analyze minute by minute data collected while breathing at different frequencies, as well as the power spectrum, as shown below
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For each breathing frequency, we report the low frequency power as well as SDNN, a feature that captures the overall oscillations in instantaneous heart rate, so that you can see differences between various rates for your tests and your clients'

The resonant frequency as determined by the app, is also highlighted in red:
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Finally, the power spectrum will report the main frequency of the session:
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A Brief History  of Biofeedback Protocols

6/3/2020

 
If you are new to HRV Biofeedback, start from part one to learn more about the foundations or part two to learn more about the important metrics to keep track of both during and outside of HRV Biofeedback sessions. Here, we’ll jump right into the most common protocols

The first standard protocol

HRV Biofeedback has been first formally defined by Lehrer, Vaschillo, and Vaschillo (2000). The authors proposed a protocol consisting of a 10−session program. According to this original protocol, a biofeedback device is needed, which is a device able to display heart rate instantaneously as well as respiration rate, at least in terms of a pacing signal which allows the user to follow a given breathing frequency. The instrument should ideally be available also for home use and not only at the laboratory
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The protocol starts with a first introductory session in which the participant is instructed about how heart rate changes with respiration (e.g. heart rate increasing when breathing in), and how biofeedback can help exercise reflexes in the body and therefore control more efficiently the autonomic nervous system (Lehrer, Vaschillo, and Vaschillo). The participant is informed that sustained practice can help improve health outcomes and manage stress

During the first session, the resonant frequency of an individual needs to be established. The resonant frequency is typically around 6 breaths/minute, but can change by 0.1–1.5 breaths/minute between individuals. Hence, each participant should try a range of frequencies and the practitioner should determine the optimal frequency by analyzing the power spectrum of each different test. Each test in this phase lasts 3 minutes, and the resonant frequency will be the one with the highest amplitude

In HRV4Biofeedback, we have introduced a resonant frequency protocol that works similarly, and guides you through a series of breathing frequencies to determine which one is optimal for you, as described here
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Read More

WHAT'S THE DIFFERENCE BETWEEN MORNING HRV MEASUREMENTS AND BIOFEEDBACK?

5/10/2020

 
Blog post by Marco Altini

HRV analysis can be used for various applications. What we do at 
HRV4Training is to quantify baseline physiological stress (what we could call "chronic" stress), and how this changes in response to training and lifestyle over periods of weeks or longer. To quantify baseline physiological stress, our measurements need to be taken in a very precise moment, which is first thing in the morning, so that we can avoid the effect of confounding factors. You can find a few examples here

By capturing changes in resting physiology, we can provide useful feedback that helps individuals to make meaningful adjustments to better balance training and lifestyle. This is particularly relevant as we all respond differently even to the same stressors depending on various aspects (how novel is the stressor, how much of that stressor we are used to take, what other stressors are present), hence only by measuring our individual response we can figure out if it's all proceeding according to our plans or not

What about HRV biofeedback then? 

HRV Biofeedback is a technique that we use to improve self-regulation, and also strengthen the parasympathetic system. While our morning measurements should be done while resting and breathing naturally, during biofeedback we use deep breathing to elicit higher parasympathetic activity

You can see your biofeedback session the same way you see your other training sessions, this is something you do so that in the longer term, there can be beneficial changes in health and performance. Biofeedback is just a positive stressor

Where do regular baseline HRV measurements and Biofeedback meet?

Normally we would recommend doing biofeedback exercises as an add on the regular morning measurement done with HRV4Training. Combining biofeedback with morning measurements taken with HRV4Training, you could see also potential changes in baseline chronic physiological stress as measured in a known context (first thing in the morning), as a result of your biofeedback sessions

BREATHING AND THE RESONANT FREQUENCY

5/10/2020

 
HRV Biofeedback requires to breathe at low frequencies (deep breathing), which stimulates parasympathetic activity. Experimental studies have found the highest amplitudes in instantaneous heart rate oscillations when breathing at approximately 0.1 Hz. This means 6 breaths per minute and is the default in the app

However, the frequency at which amplitude is maximal for a person can be slightly different.  This is what is called the resonant frequency and can vary by up to 2 breath/minute between people


Your resonant frequency can be established with a protocol that consists of breathing at different frequencies for a few minutes until the frequency that elicits the maximal amplitude is found

You can do so in the HRV4Biofeedback app, from the Breathing menu. The test will last 6 minutes and works as follows:
  • The guided breathing will change over time during the 6 minutes, going from 7.5 to 5 breaths / minute
  • You should try to follow the pacer for the entire duration of the test, which is very  similar to a regular session, but with the main difference that the breathing frequency will automatically change
  • Another small difference is that this time the timer will show a count down, starting from 6 minutes. Once the test is finished, the app will automatically stop the measurement and compute your resonant frequency, as shown in the screenshots below
  • You will also be able to see the heart rate trace for the entire recording, which normally shows larger oscillations as you do deeper breaths towards the second half of the test

While the resonant frequency test should find the optimal breathing frequency for you, you might feel more at ease with a slightly different breathing rate. Feel free to always change the breathing rate using the slider in the Breathing page, the app will use your configuration for the following sessions
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How does the biofeedback score work?

5/10/2020

 
​The score in the app represents how well you are practicing deep breathing according to your resonant frequency, as well as the duration of the exercise. You will see that if you are not focused in your session, or struggle to perform the exercise correctly, the score will not increase much over time. On the other hand, correctly following the pacer and deep breathing, will lead to a higher score over time. In general, the higher the score, the better

While the score is provided so that you can quantify the exercise, note that what matters the most in this case is the deep breathing exercise itself, and how  this might impact your baseline physiology
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GETTING TECHNICAL

In a little more detail, we currently compute the biofeedback score as follows. We first collect data for the entire duration of your session. Then, we compute the power spectrum by first ​interpolating the peak to peak differences (PP or RR intervals) at 4Hz. This step is necessary as RR intervals obviously are not evenly spaced in time, and we need evenly spaced data in order to perform frequency domain analysis. Once we have re-sampled our data, we remove the DC component, convert into seconds, and compute a hamming windowing on the time series we've got from previous steps. After windowing, we compute the FFT and then determine the power in the low frequency (LF) band, which is the main band of interest for biofeedback. Why is that? Because when deep breathing, we increase power in this window, since any breathing rate between about 4.5 to 8.5 breaths / minute, will result in a frequency inside the LF band 

At this point, once we have the LF power, we also multiply this score for the duration of the session, and then by a linear factor which allows the score to be a bit more user friendly. The whole point of this procedure is to have a score that capture well the deep breathing exercise and the fact that a longer session is beneficial (more training!)

Below you  can see an example of a power spectrum for a session of 3 minutes, you can see quite clearly how the LF band contains a large peak, which was the breathing rate of this session (6 breaths / minute, or 0.1 Hz)
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Biofeedback session: The screen

5/10/2020

 
When doing a Biofeedback  session, a few numbers and signals are shown on screen. Here you'll find a description and a few videos that should clarify any doubts you might have

​The measurement screen shows the following:
  • A breathing pattern taking the whole screen. This is the part you should focus on, following the breathing pattern with deep breaths that will stimulate your parasympathetic system
  • A top panel used to make sure your beat to  beat heart rate data is measured correctly. Here you can see the camera view, which should show a red dot if you place your finger correctly on top of the  camera, and the PPG signal. The PPG signal  represents the heart beat, and should show a smooth waveform similar to the one below. You could consider this top panel only useful in terms of signal quality, and do not really need to focus on this while doing your sessions, provided a smooth signal is being shown. 
  • A central panel showing your instantaneous heart rate. This is the most interesting bit after the breathing pattern. Here you will see the heart rate increasing when you breathe in, and decreasing when you breathe out. After 30 seconds, we will also show a graph of your heart rate over time, which should look like a smooth waveform going up and down depending on your breathing. 
  • A bottom panel including time, instructions and buttons to stop or cancel your session. This should be pretty straightforward.

​In the videos below, you can see the first few seconds of the measurement, when you should try to follow the breathing pattern, and just make sure the PPG data looks good, a nice and smooth waveform as shown in these videos. In the second video, you can also see that the heart rate graph shows up, with oscillations reflecting deep breathing, with heart rate increasing when breathing in, and decreasing when breathing out.

WHAT SHOULD I FOCUS ON DURING THE PRACTICE?

Our health and performance can be affected by how we are able to effectively cope with stressful situations and deal with anxiety, or in broader terms, our ability to emotionally self-regulate is key

The goal of HRV Biofeedback is to improve self-regulation, therefore impacting positively our health and performance

Practically speaking, HRV Biofeedback consists of providing an individual with real-time feedback on instantaneous heart rate and respiration changes while being instructed to breathe at low frequencies. This is what you see in the app, and thus the only thing to focus on is deep breathing

Pretty simple, right?

GUIDELINES AND BEST PRACTICES for camera-based measurements

5/10/2020

 
​HRV4Biofeedback's unique camera based measurement was scientifically validated and showed to be equivalent to chest strap measurements (Polar H7) as well as electrocardiography. Check out also the imagee below where we show a comparison of peaks detected from a full ECG (Cosmed, reference system) and PPG data acquired using our technology
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To make  the most of your measurement, make sure to follow these guidelines for all your measurements:
  • Make sure the flash turns on. If the flash doesn't turn on, the app won't be able to measure with high accuracy (which is the reason why you cannot measure using an iPad, unless you use a bluetooth sensor). If the flash doesn't turn on and you have an iPhone, go under your iPhone's settings (in your phone, not in the app) and make sure that HRV4Biofeedback is allowed to access your camera
  • Make sure to cover the back camera completely. In some phones the flash might be quite far from the camera. Try to cover entirely the camera and also the flash as much as you can, using only one finger. Here you can find more instructions for iPhones with 3 cameras
  • Make sure there is limited light (apart from the flash) in the room you are taking the measurement in. Measuring in dark places provides better measurement as natural light does not interfere with our algorithms, while we measure blood flow using light reflection. It should still be possible to measure accurately when there is sunlight, but in case of trouble, you might want to try a darker room
  • If you use a phone cover, remove it when taking the measurement
  • Place your hand on the camera before tapping the "Start session" button. The app will discard the first few seconds of data regardless, but placing the finger before starting the measurement can still be beneficial during the first few seconds
  • Try not to move your finger and not to change the amount of pressure on the camera. Keep your finger still and in a comfortable position. This is the most important point. While we have techniques in place to cope with motion artifacts, movement will most likely mess up your data beyond what can be fixed
  • Do not apply excessive pressure, which might impede blood flow and therefore prevent the app from measuring it correctly
  • Do not use earphones while measuring (iPhone only). Unfortunately due to some incompatibilities with the techniques we use, it has been reported that the app might freeze if you measure using earphones on iPhones.

As first time users, try to take 2-3 measurements following the advice above, and you should be able to acquire high quality data rather easily. 

WHICH CAMERA SHOULD I USE?

Regardless of how many  cameras your iPhone has, only one camera is the main camera used by the app. In the app, you can figure out really quickly what camera you should use, as you can see the camera view during the measurement. If you see a red dot as below, then you are covering the right camera, because that's your finger
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A primer on Heart Rate Variability Biofeedback

5/6/2020

 
Blog post by Marco Altini

Life can be demanding, from both a physical and psychological point of view. Our health and performance can be affected by how we are able to effectively cope with stressful situations and deal with anxiety, or in broader terms, our ability to emotionally self-regulate is key

Heart Rate Variability (HRV) Biofeedback can directly affect physiological and psychological factors through deep breathing exercises and is an ideal strategy to help us self-regulate and better cope with stressful situations

Scientific rationale

Practically speaking, HRV Biofeedback consists of providing an individual with real-time feedback on instantaneous heart rate and respiration changes while being instructed to breathe at low frequencies (Lehrer and Gevirtz, 2014)

From a physiological point of view, we can consider homeostasis as a starting point to understand the rationale behind using HRV Biofeedback. As the body via the autonomic nervous system (ANS) responds to stressful stimuli in an attempt to maintain a state of balance, we can determine how effective this physiological self-regulation process is, by measuring the ANS

During HRV Biofeedback, an individual is instructed to breathe at low frequencies. Breathing at low frequencies (or deep breathing) causes large oscillations in the instantaneous heart rate, which synchronize with breathing rate. The influence of breathing on heart rate is called Respiratory Sinus Arrhythmia (RSA) and is mostly modulated by the parasympathetic branch of the ANS (Lehrer and Gevirtz, 2014). Hence, deep breathing results in training of the parasympathetic system, which might explain at least part of the positive effects of HRV Biofeedback reported in the literature in the context of reducing stress and anxiety (Goessl, Curtiss, and Hofmann, 2017)

Strengthening the parasympathetic nervous system could also motivate using HRV Biofeedback in athletes, with the potential of improving emotional self-regulation, coping mechanisms, and performance (Khazan, 2016; Pusenjak et al., 2015)

Check out these resources to learn more about  the physiological underpinnings of HRV Biofeedback:
  • HRV Biofeedback guide
  • The science of biofeedback

WHAT'S THE DIFFERENCE BETWEEN MORNING HRV MEASUREMENTS AND BIOFEEDBACK?

HRV analysis can be used for various applications. What we do at HRV4Training is to quantify baseline physiological stress (what we could call "chronic" stress), and how this changes in response to training and lifestyle over periods of weeks or longer. To quantify baseline physiological stress, our measurements need to be taken in a very precise moment, which is first thing in the morning, so that we can avoid the effect of confounding factors. You can find a few examples here

By capturing changes in resting physiology, we can provide useful feedback that helps individuals to make meaningful adjustments to better balance training and lifestyle. This is particularly relevant as we all respond differently even to the same stressors depending on various aspects (how novel is the stressor, how much of that stressor we are used to take, what other stressors are present), hence only by measuring our individual response we can figure out if it's all proceeding according to our plans or not

WHAT ABOUT HRV BIOFEEDBACK THEN? ​

HRV Biofeedback is a technique that we use to improve self-regulation, and also strengthen the parasympathetic system. While our morning measurements should be done while resting and breathing naturally, during biofeedback we use deep breathing to elicit higher parasympathetic activity

You can see your biofeedback session the same way you see your other training sessions, this is something you do so that in the longer term, there can be beneficial changes in health and performance. Biofeedback is just a positive stressor

WHERE DO REGULAR BASELINE HRV MEASUREMENTS AND BIOFEEDBACK MEET?

Normally we would recommend doing biofeedback exercises as an add on the regular morning measurement done with HRV4Training. Combining biofeedback with morning measurements taken with HRV4Training, you could see also potential changes in baseline chronic physiological stress as measured in a known context (first thing in the morning), as a result of your biofeedback sessions

Try HRV4Biofeedback

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