Work fatigue, HRV and Neurosonic

HRV, or heart rate variability, is the most reliable, non-invasive indicator of stress, measuring the balance between the parasympathetic and sympathetic systems. Several Neurosonic users have been able to verify the positive effect of Neurosonic on heart rate variability and we have occasionally highlighted these results in our own publications. This blog post is about Firstbeat measurement data that we have received from an anonymous person, a 27-year-old woman who has been suffering from work fatigue for a long time.

What is Firstbeat?

The Firstbeat wellbeing analysis is a three-day measurement that analyses the subject’s heart rate. The subjects are sent a heart rate monitor developed by Firstbeat, with one sensor attached under the right collarbone and the other under the left rib cage. The purpose of the Firstbeat meter is to measure heart rate variability and, through it, the responses of the nervous system.

Based on the results, a graph of the electrical activity of the heart is drawn to show the body's stress responses, the amount of strenuous and light exercise, recovery and heart rate over a three-day period. Stress and body alertness are shown in red (including positive effects on alertness), recovery in green. The analysis of the graph is usually provided by the service provider so that clear conclusions can be drawn from these results.

What is HRV (heart rate variability)?

Heart rate variability, or HRV, is a physiological phenomenon that describes the variation in the time interval between successive heart rate intervals in milliseconds. Some may believe that a healthy heart beats steadily all the time, but it doesn't. Instead, when looking at the milliseconds between heartbeats, there is a constant variation.

HRV is regulated by the autonomic nervous system and exercise, breathing, hormonal responses, metabolic processes, recovery, stress and cognitive processes all affect HRV. The autonomic nervous system has two sides, the parasympathetic (rest and digestive system) and the sympathetic (fight or flight system) and these two work in opposite directions. When we think about HRV, it increases (which is a good thing) when the parasympathetic side is actively working, because the sympathetic side is the one that decreases HRV – and we don’t want that.

Neurosonic and HRV 

A report on work-related fatigue from a person who wishes to remain anonymous, as told by the service provider who carried out the Firstbeat measurement: X took sick leave on 2 March for work-related fatigue, with symptoms of difficulty falling asleep and constant tiredness. Help was sought to help her to sleep and cope, through therapeutic and medical means. After about two months, things started to improve slightly, but fatigue was still noticeable almost every day. 

Next was X's Firstbeat analysis after two months of sick leave at the end of April (Figure 1). X was feeling a little better but there was still a constant state of stress in her body. There is very little "green" recovery data.


Figure 1.

Testing the Neurosonic mattress: X’s follow-up measurement in late May (Figure 2). We had been using the Neurosonic mattress for one week. In the first week, we used 10 to 20 minutes of relaxation, about an hour before bedtime in the evening. In the second week with the Neurosonic mattress, we switched to longer relaxation according to the Neurosonic specialist's instructions, adding a power nap during the day, i.e. 10 minutes, and in the evening we added even more time, i.e. 20 to 39 minutes of relaxation an hour before bedtime.

Figure 2.

Firstbeat analysis follow-up results (week 2, Figure 3): In the measurement period, the aim was to keep the days as similar as possible to the first measurement period in order to obtain a reliable result. During the measurement period, using the mattress itself did not lead to a "green" recovery, but the main focus was on the night. During the night, X's recovery was clearly better and she felt more refreshed in the morning than before. After the second week of Neurosonic, X's general level of alertness and well-being has improved and we are looking forward to the next weeks.

Figure 3.

The third and final test period was in early July. The results are almost the same as in the second test. X has improved a lot and we were even a bit surprised that the results were not better than this. The Neurosonic programs we used were a 20 min. relaxation during the day and a 20 to 40 min. relaxation in the evening. X found them to be very good and they helped her to rest well! Sleep improved and in the morning she felt refreshed almost every morning; 6 mornings a week are now good. The symptoms of fatigue have gone and the energy has returned, X is able to exercise 2 to 3 times a week, her heart rate still rises a bit easily, but the direction is right. We're seriously considering whether the next step should be to get a mattress of our own... maybe sometime in the future.

So far, X has continued to use Neurosonic with a service provider in her hometown.

Neurosonic expert's notions on the above test period and its results

The results show that when daytime recovery is not triggered even with Neurosonic, it is a longer-term stress condition. Most likely, the person's sympathetic nervous system is in overdrive and cortisol levels are high. The client has experienced the treatments as pleasant moments of relaxation and this has a great impact on learning to relax. However, the body has been in overdrive for so long that the effects of Neurosonic would be best seen in home use, where the device would be available continuously and every day and recovery from exertion would become a daily routine. In this way, the autonomic nervous system would be more controllable and the Firstbeat measurement would not show stress reactions in the same way.

Particular attention is paid to bedtime, where a clear stress peak is seen before the Neurosonic period. This suggests elevated cortisol levels and that the person is unable to relax properly before falling asleep. The situation has improved since the adoption of Neurosonic, with easier falling asleep and much better night-time recovery. Even if daytime recovery is not shown in the measurement, the improved night-time recovery makes up for it. A longer period of Neurosonic would probably also show progress in daytime recovery.