I built the second HRV app in the App Store about 10 years ago and also played with kubios 
I think simple HRV/Rmssd is enough, using any popular HRV app like elite HRV. But it takes practice to make it reliable.
This post is in response to a question asked here
https://forums.trainerday.com/t/example-of-a-hiit-4-second-interval-automated-slope-mode-workout/826/5
My partner is pro coach and he can get in decent shape doing an hour a week. Enough to go on week long bike rides with friends and almost survive. One of the guys on his last trip invested 125 million in Zwift
I spent also a lot of time on http://www.muscleoxygentraining.com/ where senior cyclist and clever guy wrote a lot in last 6 years and did many specific tests with HRV and different devices (Polar H10 was on the list) and it looks like he knows how to find correct training levels for aerobic effort. He uses commercial version of Kubios Scientific and data cleaning is there as automated process. Without data cleaning HRV parameters will be unreliable (like DFA alfa1) and being able to retrieve it is much better then ârule of thumbâ (if you can speak) of Mr Maffetone.
Polar H10 is possibly not generating artifacts (I followed all precautions suggested by BJRMD), but ECG from Polar Logger is only âperfectâ when subject is not moving (no cycling or jumping). Hence my additional testing of ECG cleaning / correcting methods in NeuralKit2 software. It looks promising.
On line (PC + ANT+) Fitness_Dashbord also can be enough, as it provides data from live stream(s) like Polar H10 and different sensors on a trainer. I tested it already.
Bottom line is that all this is not for a layman: I can play with software as I spent already 40 years on different software platforms and I like it.
I actually started programming 45 years ago so similar to when you started. Commodore PET, VIC20 and the amazing Commodore64 were my beginnings.
Yeah, I could get highly consistent results with Polar H6/7/10 with proper technique. Mostly related to morning ritual and breathing technique. In this case not much data cleaning is needed for simple understanding of morning wellness but yes trying to predict AeT is a whole other subject and something I have not dove into. I agree this is not for the laymen. Especially digging in deep.
Itâs cool you are so motivated to learn at 75, I am sure I will follow in your footsteps.
Ha! 
Commodore Pet2000 (8 kb of RAM, I used dots create my first stocks and business indexes charts). Next one was BBC B computer, 32 kB, Commodore 64 alternative. I was able to program and print (document with all information for players) badminton tournaments (> 100 players, single, double and mixes on 2-3 spots and optimisation of available courts). I used cassette recorder for data and went through dire straits with bad magnetic tapes quality 
Of course, it is impossible today, like for it was impossible to fly to the Moon in 1969. But I did not know it.
Happy am I talking to somebody with right computer literacyâŚ
By the way: HRV is a hot topic:
Heart rate variability (HRV) as a search term on PubMed rendered âź55,000 publications as of June 16, 2022
It comes from a publication in Bioinformatics field: Comprehensive HRV estimation pipeline in Python using Neurokit2: Application to sleep physiology
But I would rather suggest much more interesting article: Heart Rate Variability in Psychology: A Review of HRV Indices and an Analysis Tutorial.
My explanation of that research explosion is ANS (Autonomous Nervous System): HRV seems an easy proxy. ANS can be used everywhere and I would invest in ANS reading (well, less then 125M USD for the moment 
).
Yes, I am fairly intune with ANS and always looking to minimize stress, which the best solution for most is quality sleep. So while science might be interested in HRV, I donât see any growth in the general publics interest in the last 5 years according to google trends. They change how they track it that that makes it look like a spike in the last year but I donât think it is or if it is, itâs not a consistent growth or big growth pattern But I think HRV is interesting but I think once you understand it, you kind of lose interest other than periods of peak training for example.
HRV is certainly a hot topic on the Intervals forum!
Reading your posts, makes me think that you might be the guy that can push it forward even faster because:
)Here are a couple of links to threads on the Intervals forum that you will probably find very interesting:
If you find this appealing, just let me (or geraldm, inigo, luisma, olly) know. A couple of core users are really trying to make it move forward but most of us lack the time or skill. We are sort of looking for someone who can make us move faster
Sapristi! (it is a French expression for surprise). Really big for me. Iâve read few days ago your discussions with Alex, but thought that you went away. OK, this seems partially true, as âIntervalsâ may have necessary ingredients I need to ingest, starting from your links.
Iâm quite busy, following few task, some relatively important: assuming that being retired means âidleâ is not matching my nature.
Iâve just started to go through âMultifractal Detrended Fluctuation Analysisâ (MFDA) on github, puzzled about fractal applications (Iâve read Mandelbrot ~ 40 years ago and tested some properties of Hurst coeffâŚ). There is a bunch of related parameters in HRV analysis and I wanted to find (any) meaning, for the moment in vain:
'HRV_MFDFA_alpha1_Width': {0: 0.9248623246889629},
'HRV_MFDFA_alpha1_Peak': {0: 1.2630889191848726},
'HRV_MFDFA_alpha1_Mean': {0: 1.405905596131884},
'HRV_MFDFA_alpha1_Max': {0: -0.02433853554792087},
'HRV_MFDFA_alpha1_Delta': {0: -0.47900762332334335},
'HRV_MFDFA_alpha1_Asymmetry': {0: -0.3455806089895147},
'HRV_MFDFA_alpha1_Fluctuation': {0: 0.0001777804423927171},
'HRV_MFDFA_alpha1_Increment': {0: 0.0465555780216021},
Ok, back to reality: you present your comments in tidy manner, which means you are possibly a professional researcher and I can obtain targeted guiding in that (hot and new for me) domain. I will follow your links, as it is appealing!
I might not have the skill (did not do any smartphone apps), being linked to âbigâ software, but letâs see.
Cheers!
I had lots of experience with bad tapes as well my first vic20i couldnât afford a drive so shut it off was time to write a new program. I was even filling my 8k with assembly code
Off course! By chance, bad tapes belong to the wrong, first part of eternity. Being able to program in assembly makes you think, that guys asking you to download 1 GB of data to run their stupid program are terrorist. 
Yes, I can recommend that crew on intervals. Itâs one of the best environments these days on exploratory endurance math and science. They donât need app developers, I am sure your old school skills are perfect. My skills are quickly becoming old school too.
Iâm Belgian, native Dutch, and fluently speaking French. Nice to see that youâre happily surprised and I never meant that âretiredâ = idle. I sometimes wish I was retired, just to find extra time for all the stuff that I would like to do. But that will have to wait another 6-7 years.
Been around here for a while and I have no intention to go away. I like apps/device/thoughts etc that shed a new light on things. That keeps us moving forward.
Not at all! Letâs be very straightforward on this. All I did was gathering information from different trustworthy people working hard on this topic from a research point. And I tried to put things together to the best of my knowledge. The only practical experience I have is the one from my own data.
A bit of background: Iâm an engineer and have been in after sales support for over 30 years. The first decade at the once so majestic Kodak company⌠Then I switched to the medical domain where Iâm active in diagnostics divisions, Neurocare, Pneumology and Cardiology. Been an amateur cyclist since my midlife crisis 
and always hungry for data that can help me understand what my body goes through during and after sports training and events. The daytime job gave me more knowledge on sports physics and access to some lab measurement tools that would have cost a fortune if I didnât have this job. Iâm also kind of a âperfectionistâ, which sometimes is good and other times, well, not so good. I gave morning HRV a first shot about 10-12 years ago, ended up with a lot of data gathered with Sporttracks but was never able to turn it in to something useful and gave up.
About three years ago, our company got the exclusive distribution on a Russian HRV product, which unfortunately still isnât successful, but my interest on the matter was woken up again. I discovered Marco Altiniâs site and started digging.
One led to the other and I started reading for days, amazed by the progress that was made. Alan Couzens, Andrew Flatt, Martin Bucheit, Daniel Plews⌠All people doing research on HRV and making their findings freely available on the net. The only problem is that there is no âoverviewâ. By the time that I got to a point where I was starting to understand the basics, I already had months of data. Then I sort of reconstructed the HRV4training plots in Excel (my programming skills are very limited, not much more then basic vba) and threw it on the Intervals forum. From there, things kind of exploded because so many people were eager to use it. David, the dev and owner of Intervals, provided the necessary programming work to incorporate the charts natively in Intervals. The iThlete training guide came next and Inigo Tolosa, the dev from the alphaHRV IQ field for Garmin, turned it into a very user friendly MatLab script baptised as ImReady4.
The evolution on the IQ field for dfa-a1 is now in an experimental stage. Since fixed a1 points had been found unreliable as intensity markers, it now incorporates respiration rate (from HRV). RR/a1 looks very promising as a proxy for lactate measurement. Inigo (an engineer /cyclist coached by Luisma) is further developing this and is backed by Luisma. They are testing the algorithms on a quite big number of athletes.
As a side project, Iâm trying to extract respiration rate from the single lead ECG that can be recorded from the Polar H10. The Fitness dashboard and ECG, which you already mentioned is what I use for recording during indoor training. Iâm in contact with Stuart, the dev of the Fitness app and a new version will come in the next weeks.
All the above + being an active member on this forum and Intervals + a daytime job + trying to be consistent in training makes me kind of âbusyâ
But I wouldnât want to miss it because I enjoy it all too much.
A helping hand by someone with mathematical insight and programming skills (be it a desktop or a phone app or whatever) could bring us even more useful tools. And if something turns out as not useful, who cares? We will still have acquired extra knowledge and skills.
Excellent! French is my second language and I spent > 35 years in Switzerland [Neuchatel] (last 18 years in Autodesk Europe, as software engineer in localisation dpt). English is my third language.
Cycling was on the bottom of my sport interests: I always preferred âgamesâ: basket ball, volley ball, badminton, uni-hockey, ping-pong. Swimming was an early exception. Running came late (40+ and first runs with Polar belt when I was over 50), rollers, SUP, a bit of cycling. Tennis popped up well over 60 (badminton style caused a lot of racket grip problems).
Here is the first hint: ECG-Derived Respiration (EDR) â NeuroKit2 0.2.10 documentation. As a brave man, you can experiment with those tools (examples are easy), by please be patient: it is not an Excel. It may takes many weeks or more, but most of useful tools are there.
I will comment / complet my answer later on: tomorrowâŚ
I think the 3 of us could all be called professional researchers We will all have an addictive job for the rest of our lives.
Now it came back from my memory that I used BBC B gameport to do a biofeedback research (skin resistance / voltage). I used my family as guinea pigs⌠It was in late 82 or 83, I think. This is really addictive. 
Wow,⌠you are more serious than me. I think my wife would send me to the mental hospital if I tried to do that. I surely would do it to myself.
I should be clear that I think HRV is very useful. Mayo clinic and the US speed skating team used to use my HRV app. I even had one lady contact me and thank me and say she believed my app helped her with her success. I looked her up and that year she won 4-gold medals.
I personally see very close alignment with HRV, deeply negative TSB and how I feel. I guess I personally am less interested in it now, as I spent about 5-years with deep fascination and because I solved the problem, I was trying to. Now actually lowest sleep HR from Garmin watch does the same thing HRV does and itâs simpler. I realize there are more depths such as finding AeT and other artificts, I find this interesting but more interested in what you guys find out
I am going to move all this to a new topic called HRV and Research addictions
I recently made up a new scientific term to describe my illness So bipolar people such as Elon Musk are very motivated during times of manic and very down on the depressive side.
I have this same tendency but it goes between up and neutral, not depressive. So scientists or doctors call this unipolar, instead of bipolar and claim itâs rare. Thatâs exactly how I feel but I donât think I go to the extreme version of this so a lower level of bipolar is âcyclothymic.â So I decided I am a âunipoolar cyclothymic.â
People tell me I should not talk about mental diseases like this in public, but this particular one is 95% postitive. The primary issue is it can be a bit disruptive to significant others but because it is not so extreme itâs not so bad and they get some benefit from it as well
I wonder if it is also my case⌠I cope well with stress: clear edge on better colleagues (from training periods) while in competitions. Neutral state I call âcontemplativeâ or âexploratoryâ: in winter time it can be a âmelancholicâ: Trivial remedy is appropriate music (or binaural beats for cerebral waves stimulation).
About 20 years ago I tested âtensâ device, being not convinced (very low current used for electrostimulation: it was for head, which is now deemed âdangerousâ). I see on Indiegogo âWorldâs Best Portable Vagus Stimulatorâ campaign for another biohack. Only 4 minutes and everything is OK again. I guess it can be tested with HRV application(s), but really Iâm not the target for that device (or not anymore).
I agree: I will say bye to my Huawei Band 4 pro, as it is not reliable for trainings. Soon I will receive and report how it behaves: âRingConn Smart Ringâ (still from Indiegogo), which resemble Oura ring without additional subscription costs. Moreover, skipping, jumping and tennis playing seems not affect the measures. But for exploration and data retrieval Polar H10 will be still necessary.