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Blog post by Marco Altini A few weeks ago we discussed a new HRV-based approach to estimate the aerobic threshold. A new paper from Bruce Rogers and Thomas Gronwald validates the method with respect to VT1 The paper is titled: "A New Detection Method Defining the Aerobic Threshold for Endurance Exercise and Training Prescription Based on Fractal Correlation Properties of HRV" and shows some neat data (male participants only), see for example VT1 vs DFA alpha 1 in the image below You can find the full text of the paper at this link  Two methods to try it yourself1) fit file and colab code: You can try this method with your .fit file (if it includes RR intervals) by loading it in my Colab (that you can find here) 2) Use the Heart Rate Variability Logger app with a chest strap to collect data The Heart Rate Variability Logger is currently the only app able to provide DFA alpha 1 in real-time.  If you try the app, make sure to configure it as follows, in Settings:
At that point, any value below 0.75 in alpha 1 as computed every 2 minutes, highlights an intensity higher than the aerobic threshold (zone 1 in a 3 zones system, or zones 1 and 2 in a 5 zones system, basically low-intensity work as typically present in polarized plans) Enjoy! Blog post by Marco Altini A new remote study investigating how the heart responds to endurance training with and without the use of recovery breaks during the exercise is about to start. HRV4Training will be used by the study participants to monitor resting heart rate and HRV each morning. Please read below in case you are interested in participating. The study is performed by Dr Neil Eves and John Sasso from the Centre for Heart, Lung and Vascular Health, within the School of Health and Exercise Sciences at the University of British Columbia. Participant Details The study needs thirty-six healthy males and females (pre-menopausal), between the ages of 30 and 48, who have been participating in endurance sport training for at least 3 years, are currently exercising at least 5 times per week, use indoor cycle training with a powermeter and heart rate monitor, and have daily access to a smart-device. You are not eligible to participate if you: have a heart, lung or brain condition, have diabetes, have a muscle or bone condition that limits vigorous exercise, or smoke Study Details The study will be performed entirely remotely (home-based)- it will involve tracking your typical endurance training over 4 weeks and performing 7 cycling-based tests of your heart’s response to exercise. The study will start and finish by asking you to measure how your heart rate responds to a maximal exercise test, a moderate intensity cycling bout and a 20-minute cycling trial. For the first 2 weeks of the study, you will perform your usual training and send your heart rate and training data files to the researchers. For the next 2 weeks, you will either repeat the exact same training, or include short rest breaks within the same training sessions. From this study, you will gain insight into how your heart responds to forms of endurance training and will have an opportunity to speak with an exercise specialist about your training programming and goals.
Blog post by Marco Altini I was recently contacted by Kow Ping, co-founder of Well Being Digital Limited (WBD101), a company which makes heart rate sensing technology for hearables, as we have been in touch regarding PPG-based technologies for HRV analysis. WBD101 makes technology which can be embedded in different products, with the goal of providing high quality heart rate data. The technology has been embedded in the Hera Leto Two earphones, sold by Actywell. Kow has been kind enough to send me a device for testing, and therefore I report here an initial validation showing really good RR intervals when compared to both our camera-based solution and our trusted reference chest strap, the Polar H7. Measurement setupData was acquired using the following devices at the same time:
During data acquisition, I collected data a few minutes while breathing freely, and a few minutes while deep breathing, to elicitate higher HRV due to RSA. You will see in the plots below visually the effect of deep breathing as we get greater swings in RR intervals. A final note on data synchronization: data cannot be perfectly synchronized because it is not timestamped by the sensors. What we can do is either to log real time and then to split data in windows based on when data was collected, then compute HRV features on these windows or to sum up RR intervals over time. For this analysis we went with the second option and also tried to visually align the data streams. As usual, if you use the camera for your measurements, please double check our camera based measurement best practices, to make sure you'll collect high quality data on which meaningful analytics can be derived.  RR intervalsWe will start by looking at RR intervals, the basic unit we need to compute HRV features. RR intervals (peak to peak differences in consecutive heart beats) are provided by the two sensors directly, so we don't really need to do much to collect them, apart from linking the sensor to the HRV Logger app and export the csv files. As a third comparison, we will add also an RR intervals time series collected using the phone camera, which is the method we have introduced and normally recommend using.  What can we derive from these data? You can see clearly almost perfect correlation between Polar H7 and Hera Leto Two and Phone Camera for all conditions (relaxed vs paced breathing as highlighted by bigger oscillations in RR intervals or instantaneous heart rate), meaning that the sensor works really well.
Blog post by Marco Altini Below we report two case studies highlighting aspects of potential physiological responses to COVID infection, which hopefully can help others identifying promptly potential issues, or tracking recovery (or impaired recovery) in the long run. 1. "Long COVID" and what happens when recovery takes a lot longer. Here is an example with HRV4Training data and rMSSD still suppressed 2 months after infection  2. acute COVID infection in a pro athlete. You can see here how large is the drop with respect to their normal values, this is how data can help to identify a problem, despite lack of specificity for a condition:  Take care and stay safe
Blog post by Marco Altini Welcome to the HRV4Training team to all our new ambassadors Full list at this link Looking forward to working together in the next months. Thank you for your support and all the best for the new year  Blog post by Marco Altini We wrote a fair amount in 2020, and I hope you have found the blogs informative. Here is my favorite 5:
Enjoy and all the best for the new year. Hopefully we'll all have a better one Take care  Blog post by Marco Altini Our work on HRV and altitude adaptation in elite triathletes is available on Sport Performance and Science Reports, at this link. This work is based on my thesis, and was carried out in collaboration with the Dutch Triathlon Federation and Vrije Universiteit Amsterdam We hope you will find it interesting  Blog post by Marco Altini In this post, I provide a short overview of HRV features. When getting started with HRV, things can get overwhelming and confusing pretty quick. One of the main reasons is probably the many different ways HRV can be computed from RR intervals, or what we call HRV features. While we have dedicated many words (and many examples) in this blog to our favorite HRV feature (rMSSD), it can be helpful to provide a short overview of the most frequently used features, so that we can better understand why rMSSD is a good choice, and what are the limitations of other methods. Keep in mind that the motivations are both physiological (what is happening in the body in terms of heart rhythm changes in response to stress) and mathematical (how the physiological processes can be captured by processing the RR intervals differently). Physiologically speaking, and making a few oversimplifications, the autonomic nervous system regulates heart rhythm, and therefore we can monitor changes in heart rhythm (HRV) as a way to measure how we react to stressors (training, lifestyle, etc.). In the context of monitoring the effect of different stressors on our physiology, both in the short term and chronically, we are interested in quantifying parasympathetic activity. The parasympathetic branch of the autonomic nervous system is the one in charge of rest functions and recovery, and therefore we are interested in monitoring it because reduced parasympathetic activity is a clear sign of increased stress and poor recovery. This will have implications in terms of the math used to compute HRV, as I'll show later on. The main features of interest can be split into time and frequency domain features, a distinction that has to do with how the RR intervals are mathematically processed. The most common time domain features are the following:
Let's get started.  Blog post by Marco Altini Below is a few months of data highlighting the relationship between the menstrual cycle, resting heart rate (HR) and perceived physical condition. For the visualization, we are using the Overview page in HRV4Training Pro, which makes it easier to spot longer term trends as it displays normal values, baseline, training load and subjective metrics, all in the same page. In particular, we can see an increase in resting heart rate in the luteal phase of the menstrual cycle, which anticipates menstruation and a reduction in perceived physical condition. This is a good example of the importance of looking at physiology + context, to better understand the full picture. As physical as well as mental stressors continuously change over time, the relationship can change. Yet, analyzing these physiological changes and properly contextualizing them (which in this case means understanding that the menstrual cycle can drive much of the change in resting physiology), can help deriving the right conclusions. The data below was collected using HRV4Training's camera-based measurement every morning. I hope you've found this short case study informative!  Blog post by Marco Altini In this blog I briefly discuss parasympathetic saturation and introduce a new feature we have released in HRV4Training Pro to allow you to determine the likelihood of parasympathetic saturation in your data or your athlete's data. What's parasympathetic saturation?Parasympathetic saturation refers to a situation in which parasympathetic activity is particularly high, but this is not reflected accurately in HRV data. As Kiviniemi et al. explain in [1], "possible physiological mechanisms underlying saturation could be due to the dose response of the heart to the acetylcholine secreted by vagal nerve ending. The dose response to acetylcholine has been considered to be linear until its concentration reaches the level at which a further increase in acetylcholine concentration does not produce a change in the response", or in Daniel Plews' words [3]: "a heightened vagal tone may give rise to sustained parasympathetic control of the sinus node, which may eliminate respiratory heart modulation and reduce HRV". It follows that as reported in another of Daniel's papers [2], "in some circumstances, such as vagal saturation, decreases in cardiac parasympathetic indices of HRV during this particular training phase can be related to positive performance outcomes and consequently reductions in HRV, so should not be viewed negatively". How can we identify parasympathetic saturation?Looking at the relationship between HRV and RR interval length you can identify possible parasympathetic saturation. Parasympathetic saturation is a rare event which can happen in elite endurance athletes during high load training blocks. In particular, parasympathetic saturation typically requires:
Under these circumstances, you can look at the relationship between HRV and the average RR interval length (basically the inverse of heart rate), to determine the likelihood of saturation. Normally, higher HRV is associated to lower HR (see data below for an example), and therefore we expect a linear relationship. However, if you are in a period of high training load and HRV is low, together with low HR, and therefore the correlation between HRV and the average RR interval length is small or negative (we lose the linear relationship that we were just discussing), parasympathetic saturation is plausible (below I'll show how you can look at this in our platform). What can you do about it?Depending on how you measure your HRV, you could be pro-active and collect data that is less likely to be affected by the issue of parasympathetic saturation. In particular:
New feature in HRV4Training Pro to determine likelihood of parasympathetic saturation for you and your athletesAs mentioned earlier, if you are in a period of high training load and HRV is low, together with low HR, and therefore the correlation between HRV and the average RR interval length is small or negative, parasympathetic saturation is plausible. We have developed a new feature in HRV4Training Pro to help you analyze this relationship. In the plot below, you would see the darker dots in the lower right corner (low HRV, low HR or high RR interval length). In this case, the suppression in HRV should not be interpreted negatively, as reported by Plews et al.: "the lack of correlation between the R-R interval and Ln rMSSD indicate that athletes are more likely to undergo parasympathetic saturation". You can find the plot below under Insights / Resting Physiology in HRV4Training Pro, we also report the correlation between HRV and the RR interval length for the past 2 and 6 weeks, so that you can more easily spot any recent changes:  Finally, we have added Possible parasympathetic saturation as an automatically detected trend, hence the system will try to do the math for you:  Is this something that should concern you?In general, parasympathetic saturation is a rare event. Over the years, I have received a few emails from users reading online that they should be sitting instead of lying down when measuring, and I just want to make something clear here: this is typically a non-issue. If you are an elite endurance athlete, and you have experienced periods of suppressed HRV, low HR, and performed well in training or racing under high loads while your HRV was low, then you are a good candidate and it would be beneficial to measure while sitting or standing. Otherwise, please do not obsess over something that most likely will never happen, and keep taking your measurements in a consistent manner, so that you can benefit the most from analyzing the data in the long term, as shown in many case studies here. If you have any doubts, you can login in Pro at HRV4T.com and check your own data. I hope you will enjoy the new feature, take care!  References[1] Kiviniemi AM, Hautala AJ, Seppanen T, Makikallio TH, Huikuri HV, Tulppo MP. Saturation of high-frequency oscillations of RR intervals in healthy subjects and patients after acute myocardial infarction during ambulatory conditions. American Journal of Physiology-Heart and Circulatory Physiology. 2004 Nov;287(5):H1921-7
[2] Plews DJ, Laursen PB, Buchheit M. Day-to-day heart-rate variability recordings in world-champion rowers: appreciating unique athlete characteristics. International journal of sports physiology and performance. 2017 May 1;12(5):697-703 [3] Plews DJ, Laursen PB, Stanley J, Kilding AE, Buchheit M. Training adaptation and heart rate variability in elite endurance athletes: opening the door to effective monitoring. Sports medicine. 2013 Sep 1;43(9):773-81 [4] Andrew Flatt's blog: https://hrvtraining.com/ Blog post by Marco Altini Quick update that HRV4Training, HRV4Biofeedback and Camera Heart Rate Variability currently support also all new iPhones from the 12 mini to the 12 Pro Max For iPhones with three cameras, the apps will use the corner camera, as shown below  As usual, please double check our camera based measurement best practices, to make sure you'll collect high quality data on which meaningful analytics can be derived. Below you can also see two minutes of RR intervals data collected with the phone and a Polar chest strap, showing the usual agreement between the two, as reported in earlier validation studies:  Here are the same RR intervals, but showing a bit better how they match:  And finally the computed rMSSD (HRV value) for the two minutes:  Enjoy!  Useful links:
Blog post by Marco Altini
We recorded our latest webinar that was put together for the Spanish Paralympic Committee. In this talk, we cover:
¡gracias! Blog post by Marco Altini As more devices are able to collect high-quality Heart Rate Variability (HRV) data during the night, a few questions come up:
In this post, I will try to answer these questions and show data that should clarify a few important aspects. In the process, we’ll have to debunk some common misconceptions.  Blog post by Marco Altini In the past few weeks I had the pleasure to get to know Francesco Cuzzolin thanks to our partnership with the EuroLeague Players Association Francesco needs no introductions, but I’m gonna do it anyway: first European to become Head Strength and Conditioning Coach in NBA (@ Toronto Raptors), formerly at Benetton Treviso, Virtus Bologna, the Russian National Basketball Team and Italian National Basketball Team, lecturer in training / re-training and injury prevention at the University of Verona and of Padova, Research and Innovation Director for Technogym, currently personal trainer for Andrea Dovizioso Francesco is also an expert in HRV monitoring, and has been using the available technologies for decades. Needless to say, we clicked In the first episode of his new podcast, we tried to break down the science and application of HRV and stress monitoring with a lot of practical insights. I hope this will be a useful resource for anyone getting started with our technology and striving to get their athletes to peak performance Link here  Blog post by Marco Altini We are starting a new research project together with CUS Torino Women's Rugby, and the University of Turin. In particular, this work aims at quantifying training load and resting physiology (HR, HRV) in the context of the menstrual cycle, looking at the relationships between these variables over several months in rugby athletes. More updates will follow, special thanks to Luca Beratto for involving us!  In the hope that we will all get to race a little more in 2021, HRV4Training is looking for brand ambassadors worldwide Are you passionate about sport and technology and have been using HRV4Training daily at least for 6 months to better balance stress? We are looking for you! We are going to select up to 30 brand ambassadors, we accept applications in English, Italian and Spanish. Would you like to spread the word about HRV4Training in another language? Send us a message with your proposal for our consideration! What do we offer to the ambassador and mentors?
What do we expect from the ambassadors and mentors?
We believe in empowering individuals with the ability to measure and interpret physiological data so that training and lifestyle stressors can be better balanced, resulting in improved health and performance Learning from athletes and coaches is an invaluable part of the journey, and we are looking forward to getting to know you and your experience To participate in the selection process, fill in this google form. Deadline is November 30th, 2020  Excited for a new partnership in the Lega Basket Serie A 🏀 Grazie Brindisi for choosing HRV4Training We wish you the best for this season! 🔬📲  Blog post by Marco Altini Last week I ran a survey on Twitter, which was triggered by seeing the data below: reduced resting heart rate during the first 6 months of the pandemic when analyzing HRV4Training data. The data shows a trend that is the opposite of what most of us would have expected. In this post, I’ll go over the data in more detail, covering changes in resting physiology, sleep, training, and perceived stress in the first 6 months of the pandemic. Read the full story, here.  Excited to announce our new partnership in the Italian Volleyball SuperLega Grazie Piacenza! 🔬📲 🏐
Blog post by Marco Altini Check out the latest paper on HRV-guided training. It is great to see reviews and meta-analysis highlighting the benefit of this approach as the field is finally maturing Science catching up with common sense is not bad either (the whole point here is to scale down intensity when too stressed), as we have covered a few times in the past (see our guide for a good starting point) Special thanks to the authors for also mentioning our work: "Currently, the development and validation of new applications (i.e: Kubios-HRV, Elite-HRV, Mobile Lab, or HRV4Training) facilitate daily HRV measurements and their quantification and, thus, the individual adaptation of training loads and recovery" Full text at this link  Blog post by Marco Altini The Overview page in HRV4Training pro shows your daily heart rate and HRV, together with normal values and baseline, to ease interpretation of your recent trends In addition, you can also color-code the bars based on annotations such as alcohol intake or menstruation, as well as based on the daily advice, coefficient of variation and detected physiological response In the latest update of Pro, available for any user when logging in at HRV4T.com, we also added a few tips and explanations that should help you better understand what could be behind a recent change in physiology, as well as how the different algorithms work Here are a few examples. Recent literature as shown that during the luteal phase of the menstrual cycle, there can be a small drop in HRV. This is now reported in Pro when selecting Menstruation as annotation, as shown below:  When selecting the Daily Advice, we report more details on how the daily advice is built:  Here is an example for sick days:  And finally for the Coefficient of Variation, including an explanation of how to read the data:  We hope you'll find the new update helpful
Blog post by Marco Altini We have made a small change to the next version of the HRV4Training app on iOS and Android to allow you to quickly hide your daily score and historical data on race or match day. Needless to say, there are days in which we might not be able to do much about our physiological stress level (for example race day), or when the value might be less representative of a poor response, and simply affected by things such as race excitement, an isolated poor night of sleep, etc. All of these circumstances can still have a psychological impact for some, especially on race day. In the app, you can always hide your score before the measurement from Menu / Settings and unchecking the "Show daily advice" box. However, it might just be too many steps to remember first thing in the morning Thus, in the next version of the app, you will be able to quickly hide your daily scores when filling in your questionnaire. First make sure to have the "training phase" tag enabled, as shown below:  Then, on race or match day you simply need to select "Competing | Hide HRV" and the app will not show you your score. On the following day you can simply select a different training phase to see your data again. Alternatively, you can always re-enable your daily score by going to Menu / Settings and checking the "Show daily advice" box.  We hope you'll find this improvement useful. Enjoy and take care!
We are excited to share the news that we are partnering with ELPA, the EuroLeague Players Association One of ELPA’s objectives is to provide its members services that help them maximise and prolong their careers Therefore, ELPA and HRV4Training are announcing a multi-year deal that will allow ELPA members to benefit from a tool which measures their heart rate variability (HRV), and provides a detailed analysis of how their bodies react to their stress levels during the season. HRV4Training app will be used to monitor physiological responses to a busy schedule made of frequent games, traveling and all that elite sport such as professional basketball encompasses Boki Nachbar (Managing Director, ELPA): “We continuously seek for ways to help our members take advantage of newly accessible technologies for professional athletes, such as HRV4Training. Especially in current climate players need to understand how their bodies react to various intense moments that happen during the season. Mastering that understanding will help them to better control the stress and it can therefore prolong and enhance their careers." Thank you and all the best for the upcoming season  Blog post by Marco Altini We are collaborating with the College of Health and Human Sciences at Kansas State University for a (remote) research study on HRV and cycling performance In particular, the purpose of this study is to determine if cycling endurance performance is altered when an individual has a change in their 7-day average heart rate variability. This study will provide insights to individual exercise prescription regarding when to appropriately decrease exercise intensity or duration in response to changes in the cardiovascular system If you are interested in participating, please read below and apply here Who can join the study?
What is required during the study?
 Blog post by Marco Altini If you have any questions or doubts before getting started with your team, feel free to send me a quick message on Twitter - we're here to help! We have modified the Coach Panel in HRV4Training Pro to allow you to display the Overview page directly in the panel, without the need to navigate to each athlete's individual pages. You can choose between heart rate and heart rate variability, as well as add color-coding based on annotations. The Overview page (more info here) is probably the most important single page in the platform, as it shows daily scores, normal values and baseline, making it really easy to quickly understand how things are trending, and how an athlete is responding to training and lifestyle stressors. As you can see from the images below, tapping "Show Overview" you will be able to see the plots directly in the Coach Panel, and save a little time during your daily check-ins. You can now also pick the type of physiological parameter (HR or HRV) and annotation (context, visualized in terms of color coding). We hope you'll enjoy the new feature, which you can try at HRV4T.com Below you can see a few screenshots of this new functionality.     |
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Marco Altini, founder of HRV4Training Blog Index The Ultimate Guide to HRV 1: Measurement setup 2: Interpreting your data 3: Case studies and practical examples How To 1. Intro to HRV 2. How to use HRV, the basics 3. HRV guided training 4. HRV and training load 5. HRV, strength & power 6. Overview in HRV4Training Pro 7. HRV in team sports HRV Measurements Best Practices 1. Context & Time of the Day 2. Duration 3. Paced breathing 4. Orthostatic Test 5. Slides HRV overview 6. Normal values and historical data 7. HRV features Data Analysis 1a. Acute Changes in HRV (individual level) 1b. Acute Changes in HRV (population level) 1c. Acute Changes in HRV & measurement consistency 1d. Acute Changes in HRV in endurance and power sports 2a. Interpreting HRV Trends 2b. HRV Baseline Trends & CV 3. Tags & Correlations 4. Ectopic beats & motion artifacts 5. HRV4Training Insights 6. HRV4Training & Sports Science 7. HRV & fitness / training load 8. HRV & performance 9. VO2max models 10. Repeated HRV measurements 11. VO2max and performance 12. HR, HRV and performance 13. Training intensity & performance 14. Publication: VO2max & running performance 15. Estimating running performance 16. Coefficient of Variation 17. More on CV and the big picture 18. Case study marathon training 19. Case study injury and lifestyle stress 20. HRV and menstrual cycle 21. Cardiac decoupling 22. FTP, lactate threshold, half and full marathon time estimates 23. Training Monotony Camera & Sensors 1. ECG vs Polar & Mio Alpha 2a. Camera vs Polar 2b. Camera vs Polar iOS10 2c. iPhone 7+ vs Polar 2d. Comparison of PPG sensors 3. Camera measurement guidelines 4. Validation paper 5. Android camera vs Chest strap 6. Scosche Rhythm24 7. Apple Watch 8. CorSense 9. Samsung Galaxy App Features 1. Features and Recovery Points 2. Daily advice 3. HRV4Training insights 4. Sleep tracking 5. Training load analysis 6a. Integration with Strava 6b. Integration with TrainingPeaks 6c. Integration with SportTracks 6d. Integration with Genetrainer 6e. Integration with Apple Health 6f. Integration with Todays Plan 7. Acute HRV changes by sport 8. Remote tags in HRV4T Coach 9. VO2max Estimation 10. Acute stressors analysis 11. Training Polarization 12. Lactate Threshold Estimation 13. Functional Threshold Power(FTP) Estimation for cyclists 14. Aerobic Endurance analysis 15. Intervals Analysis 16. Training Planning 17. Integration with Oura 18. Aerobic efficiency and cardiac decoupling Other 1. HRV normal values 2. HRV normalization by HR 3. HRV 101 |
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