Heart rate variability (HRV) in real life

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A lot has happened in the last six months – as you can see in my morning HRV measurements with HRV4Training and MySASY.

My morning routine

After having tested and compared many HRV measurement systems, I got stuck with two products: HRV4Training and mySASY. Every morning I first measure for two minutes with HRV4Training in a sitting position and then do the orthostatic measurement in a lying and standing position with mySASY.

The hope behind this is to be able to derive decisions for my training from the measured values. Am I recovered enough for the next hard training session? Is a cold coming on? Am I training too much or too little?

Why do I use two systems for this? In principle, of course, it is perfectly sufficient to use only one. But since the approach and thus also the statements of HRV4Training and mySASY are very different, I use them in parallel mainly out of curiosity.

So far, however, I have not looked at them in a direct comparison to decide whether I might want to stay with just one of them. But since there were many events in the last six months where the support of an HRV system was useful, I am now doing a practice comparison.

The last six months


I chose this period because about half a year ago I was preparing for my first competitions again after a long injury break. Then there was illness, holiday, Corona, a break from running… But one thing after the other:

Break in running (March 2022)

Actually, I was already training quite well again after the Christmas break, when I had to take a break due to an ENT operation. No exertion for a week – unfortunately followed by a week of illness.

Workload in WKO5

HRV4Training shows relatively normal values in the first week and then a clear dip in the second week due to the illness (red bars).


In my own evaluation of the HRV4 training data in WKO5, you can also see the course of the resting heart rate (lower line). Here, too, you can clearly see the deterioration (i.e. increase) during the week of illness. In addition, you can see that the HR was still elevated more than a week after the illness, even though I only gently returned to training.

HRV evaluation in WKO5

With mySASY, the downward trend is also clearly visible, but poor values only occur during the second week. In contrast to HRV4Training, mySASY includes not only the parasympathetic nervous system but also the sympathetic nervous system in its measurements. So I not only find out how recovered the body is, but also how activated or ready for action it is.

According to this, I was ready for training again one week after the break – while HRV4Training thought I was ready on the first day. Looking at the resting heart rate, I think HRV4Training’s assessment is a bit too optimistic…


In the aggregation of the data, however, one can see that the platforms do not disagree at all if one looks at the 7-day trend (blue curve) rather than the daily recommendations (bars) at HRV4Training.

The bottom line is that both apps clearly showed me the illness – which I also noticed without. 😉 For the more important question of when I should get back into training, mySASY was much more helpful.

Competition preparation (April/May 2022)

I then prepared for the Venloop (15.05.2022) and included the run in Nordkirchen (30.04.2022) along the way. It’s not easy to see in the graph, but there are many days in the build-up with marginal high loads (yellow dots), which come from an increase in volume and intensity that is a bit too fast (for me at that moment).

Workload in WKO5

According to HRV4Training, the adaptation to these loads was ok. There is only a small dip in the middle of the block when I increased the intensity. But I seem to have coped well with that too.


At the same time, I can see my resting heart rate dropping. A consistently good HRV with a falling pulse is a good sign that the training adaptation is working well and that my fitness is improving.

HRV evaluation in WKO5

mySASY sees it similarly, but clearly shows me the need for recovery days (red dots). The green dots (supercompensation) also become less in the second half. So it could have been a little less intensity. In the week before the Venloop, you can clearly see how the tapering works.


Both tools confirmed to me in this phase that I was coping well with the training stimuli. However, fine-tuning the load would only have been possible with mySASY (more green points = super compensation).

Lack of sleep (May 2022)

I slept badly during the two weeks immediately after the Venloop. Especially in the first week I had restless legs and I often got up at night. In the second week it slowly got better.

HRV4Training acknowledges this time with clear warning messages (yellow and red) and advises to cut back on training or even to take a break.


As you can see from the workload, I took it very easy during that time. So there wasn’t much to do about the training.

Workload in WKO5

My resting heart rate has also continued to drop. So the lack of sleep does not seem to have had a big effect on the overall system.

HRV evaluation in WKO5

But mySASY also clearly points out that no good training adaptation took place during that time. Intensive sessions would have been useless because the body was not ready to process these stimuli.


For me, HRV4Training and mySASY were equally helpful. Without their advice, I would have run more intensively despite being tired. It was certainly better to give the body more rest.

Holiday (July 2022)

We were in Mallorca for a fortnight in July. It was all about relaxing by the pool and on the beach – but at 34°C… When I look at the values in HRV4Training, it must have taken me a week to get used to the temperatures.


I only went running a few times, but I played beach volleyball almost every day. So the workload was there even on holiday.

Workload in WKO5

I only used mySASY very irregularly. There was actually no load to control and the measurement often did not fit into the morning routine of a hotel room with four people 😉 But it was enough to confirm a good recovery.


Corona (July 2022)

Immediately after the holiday, I caught the virus. Within a week it went steeply downhill, but also directly uphill again.


In order not to take any risks, I then took another two weeks off. After one week I would have been ready to run again, but common sense prevailed.

Workload in WKO5

The HRV remained low for a long time and the resting heart rate was clearly elevated. But there were other reasons for this (see next chapter).

HRV evaluation in WKO5

If you report a sick day to mySASY, the app asks you to take a break from measuring until everything is OK again. Of course, you won’t control any training during this time – but you don’t get an answer to the question of when you can start again.


Heat (July/August 2022)

Despite heat acclimatisation on holiday, temperatures above 30°C were too much for me at home, too. Of course, that didn’t help with Corona recovery.


After the two weeks break, I started again very moderately (supported by Enduco). I definitely felt like training again – but clearly not in the heat…

Workload in WKO5

What bothered me most was the lack of rest at night. While I had an air-conditioned room on holiday, it was still far too warm at night in my bedroom under the roof at home. You can see that clearly in the HRV and resting pulse values.

HRV evaluation in WKO5

As you can clearly see on mySASY, however, the load was well dosed during the re-entry despite the heat.


In the direct comparison of HRV4Training and mySASY, the partially different statements of the systems are clearly visible. Especially in the last two weeks of the observation period.

HRV4Training and mySASY combined


So far, I have been using both systems in parallel rather on a gut feeling. I have not made a real comparison, so the result of this small field test is also exciting for me.

Above all, it has become clear to me that HRV4Training and mySASY do not make the same kind of statement. HRV4Training is representative of all HRV apps that are based on the measurement of the RMSSD (EliteHRV, Kubios HRV, Vitalmonitor, …). This makes it possible to make statements about the body’s state of recovery, to which the training loads only contribute in part.

In my case, the lack of sleep and the resulting reduced recovery seem to have a direct and major influence on the values.

Stresses from training, on the other hand, have a more long-term effect – probably also through poorer sleep after a hard training session in the evening and the cumulative, reduced recovery.

While HRV4Training tracks the general (recovery) trend well, mySASY is much more focused on training readiness and training adaptation. Alarm signals (illness) are recognised well in everyday training. But without training stimuli it is difficult to estimate when training could start again.

On the other hand, mySASY provides much more helpful information on load control. What I can only observe as a trend after two weeks with HRV4Training, becomes clear with mySASY already in the course of the training week. Often even after one or two training sessions, because the app usually seems to be right in its assessment of the adaptation on the day after the workout.


Based on these experiences, I would recommend mySASY especially for the (also short-term) training and load control of ambitious athletes. From the morning measurement, concrete decisions for the training can be read, which are not necessarily also to be taken from a good body feeling. For the system to work well, however, it needs 3-4 load days per week. I did not find mySASY so helpful during rest periods.

HRV4Training is more universal and not as precise for training control. I would not want to base my training decisions on a single morning measurement. But the weekly trend shows very well whether you are on the right track with your current training load. Other events such as illness and lack of sleep are much better recorded. I would also want to assess the return to training after an illness on the basis of the HRV4 training values.

    1. Hi Stepan, I no longer use mySasy. The free version of HRV4Training offers everything I need. The added value of mySasy has not paid off. Alternatively, I really like Garmin or Suunto as night-time recovery trackers.

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Hi! It’s me, the Harlerunner.

This is where Thomas Pier writes about running and (much more than just the necessary) equipment. I don't run particularly fast or far. But I like to share my experiences as an ambitious recreational runner, curious early-adopter and as my own trainer.

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