There's a lot, and it depends on a) your desired outcome b) your budget c) your pathway to publication d) your sample size e) how good you are with hardware f) how long you want monitoring for g) what add-ons you need to measuring heart period, and so on.

But let's approximate: for most applications, you need a single lead ECG with a reasonable bit rate and sampling rate that gives you access to raw data. There are a LOT of laboratory brands, including but not limited to:

ADInstruments

Biopac

Mindware

Thought Technology

Contact Precision

James Long

Any of these companies make hardware that has been used a hundred times before. However, they won't be as cheap as newer devices.

A reasonable intermediate product is the eMotion Faros. Nice build, stripped down functions, good accuracy. I saw some test data from these, it was well filtered and accurate.

Depending on your level of confidence, Bitalino and MobilECG both make cheap, accurate hardware but ones which have higher technical demands for use. If you have any engineering background or you have good consultant IT people, though, you will find them very easy to use.

Don't get a sports watch with HR functionality (e.g. Suunto or Polar). As much as the basic signal might (occasionally and under the right circumstances) be accurate enough, they RR intervals and not a raw ECG. This is a disadvantage which affects your ability to determine the accuracy of the data. These days, due to advances in sensor and microprocessor tech, integrated circuits etc. these watches are no longer a 'cheap' solution. In fact, they're now more expensive than other fully functional ECGs. 

FitBit, Mio Alpha, or other wrist-mounted devices are right out.

Don't get anything which takes measurements by optical pulse / blood flow, piezo, or ballistic movement unless you're recording from a massive sample which demands you buy several multiple devices.

Don't buy any form of Holter monitor unless you absolutely need multiple leads over longer time periods.

Finally, there is an excellent psychophysiology group at KU Leuven who may be able to give you local advice. I'm sure they can get you in touch with local product reps etc.

Standard plethysmography is not included?

unfortunately this system is not running , I cannot answer

what do you exactly  mean by a validated device to measure HRV?

Are you looking for a device that measures ECG, then internally finds the IBIs and calculate HRV indices and just give those outputs to you? (i don't know about such a device) and I personally do not recommend any hard-coded/not-open-source device as a validated measure of HRV. Although it depends to how precise you want to measure HRV.

Or you are looking for a portable ECG device which only record ECG signal. later you can download the ECG data and get the HRV measures by  its own customized software or any other software?  in this case have a look at NeXus 10 MKII. 

here is the link:

http://www.mindmedia.info/CMS2014/en/products/systems/nexus-10-mkii

In Health Psychology KU Leuven there is one. you might like to have a look. 

By portable I assume that there may be recording during movement which highly increases noise and artifacts. So, as Hassan suggested, and based on my experience of working on 24-hour Holter monitoring ECG data, I also suggest to not rely on any device that automatically gives you HRV analyses. Instead, process and edit your recorded signal in some well known and easy to use software such as Kubios and ARTiiFACT and then work on the HRV indexes. Also, pay attention to the sampling rate of the portable device that shouldn't be less than 500 Hz based on the guidelines.

The NeXus 10 MKII suggested by Hassan is a good choice. It can give you HRV analyses and raw data at the same time and you can check how valid it is. You can also record other physiological measures such as breathing etc. It is however more expensive than simple Holter monitoring devices and if you do not need other measures, I recommend the later one.

Thank you very much for your answers and suggestions. I have performed studies using the Nexus 4.. And it worked well! But I really want a portable device and indeed, the Nexus 10 MKII looks as a good alternative. I am also convinced that I need to start from the raw ECG data and analyze HRV myself. Thank you for all suggestions, however if anyone knows an even smaller device than the Nexus 10 recording up to 8 hours at once, I am open to it.

Marijke,

Assuming it's a question pertaining to humans.In clinical medicine we do this all the time. We use Holter monitor x24 hours or Zio patch x upto 14 days. 

RD

you can use smartphone for this

https://play.google.com/store/apps/details?id=com.hrvfit.ithlete&hl=pt_BR

https://play.google.com/store/apps/details?id=com.cardiomood.android.expert&hl=pt_BR

Dear Marijke,

if you need a portable and reliable device to acquire ECG and respiratory signal, while performing HRV analysis yourself, I would greatly suggest a telemetric device I have been using from years.  You can find more detailed info here: http://www.francescomarazza.it/BT16Plus.html

Sincerely,

Nicola Montano

We are currently using Firstbeat Bodyguard 2 devices and they work really well: http://shop.firstbeat.com/

By the way, as to the validation of devices, the results from one study we carried out with the Firstbeat devices were published in the International Journal of Psychophysiology, http://www.sciencedirect.com/science/article/pii/S0167876015300106

There are at least ten parameters related to HRV ->

HRV time based: HR, SDNN, RMSSD, pNN50

HRV frequency based: TP, (VLF), LF, LF n.u., HF, HF n.u., LF/HF

I have already evaluated studies for Pfizer and GSK. My recommendation is: use a datalogger with 1000 Hz or 1024 Hz for ECG recording and evaluate HRV from the ECG records using MATLAB or SCILAB. Which parameters are important for your research?

If you really want to have reliable data, use a 8000 Hz spezialized HRV device.

see here: www.joysys.at

and ask for research conditions

kind regards

Max

Dear Marijke, 

I'm president of Intellewave, inc and Heart Rhythm Instruments, Inc. My system  Nerve-express (www.nervexpress.com ) validated in Columbia University with excellent result. As I know no other system based on HRV validated on such of high level. my contact info is on my sites. Any question do not hesitate to contact me.

Best regards.

Alexander

I have experienced Nerve-express for research purposes in a lot of experimental conditions. I confirm to have found this sytem the most excellent method of HRV investigation and I use it currently . It is the only system that is articulated and   is able to give simultaneously a look at the ANS and at the cardiovascular system. In my opinion  It is the best .  I benefit of this occasion to request to Dr. Riftine to have the time to contact me since the next step entering in my direct competence could be  to complete the method using also non linear, chaotic and fractals techniques and I have the appropriate methods and competence  to do this with advanced methodologies . On the other hand I repeat that  I have used Nerve-express from several years and I have no doubt that it is the most valid not only at reserach level but also at clinical application. Nerve -express needs all the appreciations.

Does anyone have any updates to this question? I am looking to purchase some equipment to measure HRV and RSA in a pilot randomized controlled trial of yoga for older adults with mild cognitive impairment and cardiovascular risk factors for dementia. Ideally the equipment could measure HRV quickly, accurately, and not be too expensive. Tips on software for data analyses are also appreciated!

Hi Kelsey,

I'm doing an ambulatory HRV monitoring study using the Bittium Faros device: https://www.bittium.com/products_services/medical/bittium_faros.

Not too expensive (around $800 US) and ships from Canada. It records ECG (which produces more accurate HRV data than photoplethymography) for up to six days on a single battery charge. I use the exercise strap (see page 8 of the attached manual) and generally get very clean ECG recordings in spite of a lot of participant movement. The device also has an embedded accelerometer which records movement.

The down side of this device is it doesn't record respiration. If you want to measure breathing try the Zephyr: https://www.zephyranywhere.com. The battery won't last as long but if you're just recording single yoga sessions you'll be fine.

For analysis, try Kubios: http://www.kubios.com. Their software is fairly easy to use, and not too expensive. Kubios' limitation is that it doesn't allow you analyze movement or respiration data, it just does HRV. Many people use Kubios for their HRV analysis and process their movement and respiration recordings in Matlab. There are other programs out there that do it all, but they a significantly more expensive.

David

I am currently looking into ANSLab software.

http://www.emotion-salzburg.org/index.php/en/anslab

Kelsey, I'd agree with David. The Faros device is (relatively) cheap for measuring ECG - and very portable. And Kubios is a solid piece of software. The older free Kubios software would allow import of ECG data, the new free software only allows import of R-R interval data. But the new PAID version ($329) also includes some useful added features, such as "ECG derived respiration ".

If you haven't already read it, there is an excellent 2017 article by Laborde, Mosely and Thayer called "Heart Rate Variability and Cardiac Vagal Tone in Psychophysiological Research – Recommendations for Experiment Planning, Data Analysis, and Data Reporting"

https://www.frontiersin.org/articles/10.3389/fpsyg.2017.00213/full

...It's the most thorough and helpful article I've EVER read about HRV. HRV is one of those measures that seems fairly straightforward until you start delving into it more carefully. They've done a great job of sorting through the various issues and providing solid recommendations that will hopefully lead to better studies and more consistent methodology.

I plan to use Bittium Farros (180) for 24 hour measurement. May I request some help on how to interpret the data for (a) healthy individuals (b) Sportsperson - for understanding fatigue and activity data (c) for individuals with autonomic dysfunction (or metabolic syndrome) e.g. diabetes. Appreciate some advise on how to use kubios and do further analysis and more importantly the interpretation of data (e.g. differences between the group on SDNN or analyzing total energy etc). Thank you in advance.

Marijke, it's been a while since you've posted your question, so a lot has happened since then. Nevertheless, we’ve built Aidlab (www.aidlab.com/research), a 24/7 health monitor, to help you do just that—do a research based on HRV readings.

With data from Aidlab, you can get a glimpse at your bodily functions as well as fluctuations of your biosignals during everyday routines (i.e. sleeping, working, running errands, or working out). You can start your experiments as a data scientist once you’ve gathered a solid dataset or by working with stream data that the device collects in real-time -> (www.aidlab.com/research).

If R-R analysis must be used for clinical purposes and not for research, one must provide VALIDATION of the devices and of the software analysis.

We made a device that provides decent HRV data, for low or moderate physical activity it is very reliable. Available here: https://igg.me/at/uecg (for research purpose you might want $99 option). If you want some particular HRV parameter calculated on-board, write me - I can add it into API if you'll request it before mid-August 2019 (or you can add it yourself any time, since the whole thing is completely open source)

Dmitry, thank you for the link ... I believe the device is worn upside down in one of the animations on the page

https://ultimaterobotics.com.ua/img/ecg_r.gif

Well, yes, but it depends on what you call up and down :) Since it's only a 2-lead, single channel unit, you can wear it in very different positions in order to see different aspects of the signal. To me, this position gives a more clear visual of P peak - although it's obviously not a standard one

Hi, may I ask you among the suggested devices what is the best to measure arousal activation (RSA and HRV) during face-to-face interactions? In particular I need it for mother-infant interactions so it has to be suitable also with infants and children. Thanks for your help!

Dear Maria, it is not a problem of devices but of analysis . It is necessary a cross-over analysis . May I suggest to see my papers on RG and to contact me? . Yours, Elio.

We hadn't studied any similar cases yet. But uECG provides a detailed HRV stats: 15-bin histogram of HRV with 1% steps, and it also outputs 2ms-precise R-R intervals (in addition to raw ECG data captured at 976 Hz rate, which could be analysed if you need more than R-R). I believe it should be good enough for such analysis

Cardiomood app and H10 polar chest strap validation

Preprint Validity of a Smartphone Application and Chest Strap for Rec...

For wearable device using smarthphone app. what are the regulatory requirements to use them in clinical trials considering that not being approved (cleared) by regulatory bodies for clinical indications (screening/diagnostic). I believe most of them are in the market as a wellness app not as a medical device. any thoughts?

Considering only one lead of a continuous record of the ECG is enough to measure HRV, wouldn't a Backyardbrains device be a good option? I know it's been designed for classes, and I haven't seen any scientific paper using it, but I'd like to know if this could be an option.

Thank you!

Our Nerve-Express device www.nervexpress.net is validated in Columbia University with excellent agreement comparing with the gold standard of Spectral analysis of R-R intervals variability - Chronos algorithm developed jointly by Harward University, Columbia University and MIT. Validation study is available.

Best regards.

Alexander Riftine, PhD