Check this page for an overview of HRV4Training's main features. Then browse the list of FAQ in this page. Each question points to comprehensive blog posts where we discuss each topic in greater detail.
For the camera version you will need an iPhone 5 or later (all versions). The 4S is not supported anymore. If you use a bluetooth low energy sensor, any device will work, from iPads to iPods and iPhones 4S. Just make sure you use a sensor that is reliable, for example a Polar H7.
What sensor should I use?
Short answer: rely on the phone camera or get a Polar H7. Long answer: read this post where I compared wrist worn sensors (e.g. a Mio Alpha) and chest worn sensors (e.g. a Polar H7) to a regular ECG device.
How accurate is the camera version?
The camera version is as accurate as a Polar H7 or a full ECG, as shown in this post. Check out also the post below where we show a comparison of peaks detected from a full ECG (Cosmed, reference system) and PPG data acquired using HRV4Training:
Most importantly, check out the next FAQ for tips on how to use the camera properly, since it does take a few measurements to get familiar with it. You can also practice any time from Menu / Resources / Camera measurement practice mode.
What's the best way to use the camera measurement?
See this post for a series of tips on how to make the most out of your camera measurement.
When should i take the HRV measurement?
Short answer: in the morning, right after waking up, so that you can limit the effect of other stressors, similarly to what we would do in laboratory protocols & clinical studies. Long answer: read this post in which I cover HRV measurements, context and time of the recording.
How should I breathe?
Short answer: relax and breathe freely. Self-pacing seems to be ideal, as each person might have a preferred way of breathing. The important point is not to force your breathing or make any effort to try to breathe particularly deep or in an unnatural way. Simply relax and self-pace your breathing.
Long answer: for a broader discussion on this topic, check out this blog post.
Can I measure multiple times per day?
No, at the moment you can measure only once per day. Making HRV measurement a morning routine, and being consistent (see this post) are key factors to make sure your data can be used to perform meaningful analysis. This being said, if you are a HRV4Training user and would like to experiment more, we are happy to send you a promo code for Camera HRV, so that you can download it for free. Just email us at this email address, specifying your current HRV4Training registered email.
How long should the measurement be?
Short answer: 60 seconds are sufficient for a reliable measurement of rMSSD and therefore of HRV4T Recovery points. Long answer: read this post in which I analyzed HRV measurements from 10 seconds to 5 minutes, to determine the reliability of different time windows.
What is the daily advice and how is it computed? What can it tell me?
The daily advice combines your HRV with respect to your normal values, your subjective scores and your recent trends to provide daily guidance. You can find out more at this blog post.
Why is my heart rate fluctuating so much during a measurement?
In HRV4Training what we measure are beat to beat differences (also called RR intervals), and what we show is instantaneous heart rate. RR intervals cover a broad range during a breathing cycle, you might also have noticed that while breathing out the instantaneous HR lowers, while it raises while breathing in. You might be surprised by the big range of values covered while measuring using HRV4Training because normally most devices measuring HR through an app, show you averaged data, such as HR averaged over the past 15 or 30 seconds. By definition, your average heart rate over the past 15 or 30 seconds is much less jumpy.
As we measure HRV variability, we prefer to provide instantaneous heart rate as visual feedback instead of averaged heart rate. Check out the data below for an example. As you can see RR intervals go from 1000 to almost 1800ms. Heart rate is the inverse of the RR interval over a minute, so we can derive instantaneous heart rate as 60000/1000 = 60 bpm and 60000/1800 = 33 bpm. This is an extreme case of high HRV, showing a variation of almost 30 beats over a breathing cycle. If we were to take the past 15-30 seconds and show average heart rate, you'd probably see something in the range of 40-50 bpm, as other devices would report it.
Note also that when using a chest strap the same relation holds. The standard bluetooth low energy protocol provides data in a packet which starts with your average heart rate, and then appends all RR intervals detected in the past second (zero or more). Most apps would take the heart rate sent by the polar and display it, thus showing you averaged information. On the other hand, HRV4Training takes the last RR interval received and computes your instantaneous heart rate as shown above, to provide you with real-time feedback on beat to beat variability.
Should I do single or orthostatic measurements?
Short answer: single HRV measurements are sufficient to monitor day to day training load and recovery. Long answer: read this post in which I analyzed data from HRV4Training users, showing that single measurements, either lying or standing, provide accurate assessment of training load, while "traditional" orthostatic measurements do not seem to provide additional help in guiding day to day training.
What are normal values for HRV?
HRV normal values cover a very broad range and tend to lower with age. While some parameters like age and fitness influence your HRV, your baseline is also affected by other factors more difficult to measure, such as genetics. For a more detailed discussion on normal values, check out this blog post (and this older one).
What are the HRV4Training Recovery Points and what features should I look at?
Recovery Points are based on rMSSD. In general try to look at rMSSD or HF as features representative of parasympathetic activity, both of them showing higher values when you are in a more relaxed, less physiologically stressed state. See this post for more details. There are some advantages in focusing on time domain features, such as rMSSD, you can read more in this blog post.
Is HRV4Training performing any correction for ectopic beats and motion artifacts?
Short answer: yes, HRV4Training performs RR interval correction to deal with ectopic beats and motion artifacts. Long answer: see this blog post to find out more about RR interval correction, ectopic beats, motion artifacts and how we deal with these issues in ECG, Polar and PPG data. EDIT: we recently improved our algorithms using more complex methods able to deal better with artifacts without overcorrecting in individuals with particularly high rMSSD. Feel free to contact us if you'd like to know more.
I measured twice in a row and my measurements were different. What does it mean?
Daily measurements taken in succession can vary, and variations of 5 - 20 ms or 0.5 recovery points are perfectly normal, simply because our physiology is never in the same state. Thus, HRV4Training uses your historical data, as much as the past 2 months of data, to understand what are normal variations for you and provide meaningful daily advice regardless of these variations.
For a broader discussion of this topic and some data from our clinical studies showing the effect of measurement duration and paced breathing on measurement repeatability, check out this blog post.
What can HRV4Training offer beyond daily measurements?
HRV4Training provides data analytics that let you explore:
Acute HRV changes in response to training: systematic analysis of day to day changes in HRV on days following training. The goal is to move from anecdotal evidence (e.g. I did intervals and my HRV the day after was low), to a systematic analysis that lets you understand better how your body responds to trainings of different intensities. Are you physiologically rested after rest days and easy training? Can you consider recovery runs as such in terms of having a positive effect on your parasympathetic activity? What drop in HRV can you expect after an intense training?
HRV trends: provide more insights on the big picture. Look at baseline changes on multiple parameters relevant to your physical condition (e.g. HRV, HRV, coefficient of variation, training load), etc. The app can automatically determine if your recent HR orHRV trend is changing in a trivial way, or if the change is something to take more seriously, based on your historical data.
Correlations: mainly for exploratory analysis inside the app. Look at what factors are related to physiological changes, and try to adjust your lifestyle accordingly (a good one is typically sleep quality).
Training load analysis: you can pick the metric most representative of your trainings (e.g. TSS, Suffer Score, training distance or your own custom metric) and analyze fitness & fatigue, determined as chronic and acute training loads, as well as readiness to perform and injury risk.
VO2max estimation: for runners using the Strava integration and training with a HR monitor, HRV4Training can estimate cardiorespiratory fitness level (VO2max). Check out this post for more details.
Check out the quickstart page for an overview of these features.
How does the alarm / reminder work?
Reminders were not included HRV4Training for a long time, mainly because we think they do not really work when timing is so important for consistency. You probably wake up at consistent times but not always at the exact same time and a reminder would always be at the same time.
Nevertheless, we recently introduced local notifications as reminders, and here is how they work: as we cannot schedule a regular alarm, similarly to the iPhone alarm clock app, but only use local notifications, you will see HRV4Training notifications do not trigger sounds if your phone is in vibration/silent mode. However, the notification stays in your screen and shows up together with your other notifications, and therefore it can still be useful if you grab your phone first thing in the morning and see it. Hence, we decided to include it this way, hoping it provides some help.
Does HRV4Training share data with other apps & services?
When authorized, HRV4Training can share data with the following apps and services:
Strava: HRV4Training can read your workouts summaries, show them in your History page and fill in automatically some of the training-related tags for you, as explained here.
TrainingPeaks: HRV4Training can send HR and HRV data to TrainingPeaks, as explained here.
SportTracks: HRV4Training can send HR and HRV data to SportTracks, as explained here.
Genetrainer: HRV4Training can send HR and HRV data to Genetrainer, as explained here.
Health: HRV4Training can send HR and sleep data to the Health app.
When are you releasing an Android version?
Short answer: We do not plan to release an Android version of HRV4Training.
Long answer: HRV4Training uses complex signal processing techniques to provide reliable HRV measurements using only the phone camera. Unfortunately, due to much fragmentation on Android (different brands, phones, android firmware versions, cameras, etc.), it is basically impossible to provide a reliable camera-based product. As iOS provides a more standard platform, development of accurate algorithms as well as maintenance of such algorithms is something we can handle with our resources, as we have done since 2013. An Android product would not work in more than a handful of devices, and would require constant work for suboptimal results. Thus, we will most likely be always an iOS product only.
As Android-based alternatives to HRV4Training, we highly recommend Elite HRV.