PART 4: The Moodmetric ring stress measurement and understanding the data

This article series tell about stress and ways to measure it. Parts 1 and 2 describe the fight or flight reaction and how the body reacts to chronic stress. Methods for long term monitoring are presented in part 3. In this article we explain the Moodmetric ring measurement and how to interpret the data.

The Moodmetric smart ring measures electrodermal activity. It detects skin conductance with the band of the ring that works as electrodes. The band consists of two silver coated steel rings, and an insulator band in between them. 

Electrodes need to get a good contact with an area on skin where the eccrine sweat gland density is high. This varies from 400/cm2 on the palm to about 80/cm2 on the upper arm. A ring form for the Moodmetric sensor has been chosen to reach the best possible accuracy. The measurement point is on the palm side of the finger and at best the signal is unbroken.

The ring measures continuously and stores the data inside the ‘stone’. The mobile app does not need to be on, nor the phone near the ring. When the app is opened and the calendar icon chosen, the ring sends the data to the app via bluetooth connection. The measurement and data storing to the ring continue immediately. The real-time signal can be followed any time with the app.

Research by the Finnish Institute of Occupational health (2015) shows that the signal of the Moodmetric ring is comparable to that of a laboratory device. The ring is applicable for field studies.

The Moodmetric signal

The Moodmetric signal is the violet curve on the mobile app that can be observed real-time. It is the raw measurement signal but auto scaled in order to have the whole amplitude visible even during strong reactions.

The curve enables analysis of single reactions. Even a thought can cause a peak: excitement, idea, awe – each reaction forms a peak within a 1-2 second physiological delay.

Interpreting the raw signal requires expertise in the measurement method and understanding the possible sources of error.

The Moodmetric index

The electrodermal activity (EDA) raw signal is difficult to interpret and prone to errors. Strong reactions can easily be spotted on the curve,  but mathematical methods are needed for further analysis.

The Moodmetric index or the Moodmetric level has been developed to solve challenges related to EDA measurement. The algorithms count an index from 1 to 100 so that 1 is the lowest the person can reach. This is possible e.g. in deep sleep. 100 is the maximum arousal, strongest possible reaction of the person. Finding the min and max takes about 12 hours, which is the calibration period. The ring can be re-calibrated e.g. when changing from one user to another.

The Moodmetric index/level tells the activity level of the person at a certain moment, looking at a few minutes´ time window. The level does not indicate single reactions but changes fast if the arousal level of the person increases or decreases rapidly. E.g. increasing is first seen in growing amplitude and raising trend of the Moodmetric curve, then in higher Moodmetric level.

It is easy to get to 100. What is more interesting is to make rehearsals that aim to calm the mind, to get the index as low as possible.

In counting the Moodmetric index, the algorithms minimize the effect of finger’s movement and the skin normal moisture level on the measurement. The index is comparable between users. If two persons are at a same situation it is possible to observe which one is calmer.

There is no momentary optimal value

It is normal that the Moodmetric level fluctuates between 1 and 100 during the day. No momentary value is good or bad.

Important is also to know, that the Moodmetric measurement does not tell whether a reaction is positive or negative. The Moodmetric ring is not an emotion detector.

The fluctuation of stress levels is individual

There are people who react fast and strong, while others respond more calmly. For instance creative people are often very prone to stimulus and they get a lot of new ideas. This can be seen in high Moodmetric levels as well as big fluctuation. A person doing work that requires deep and long concentration might have low Moodmetric levels throughout the working day.

The levels can be high due to excitement and energy, or low due to good focus. All this is positive. The levels might also be high due to pressure and lack of control at work. Low figures in turn can tell of boredom or even depression. The measurement data always needs the ring wearer´s own perception of the situation. No one else can tell whether the 100 on the mobile app tells of excitement or irritation.

A good team is heterogeneous also by the way they react

At workplace it is good to have people with different ways to react. A team with individuals that all have a very mild or a very strong natural way to react, probably is not as productive as a more heterogeneous team.

The Moodmetric measurement helps to understand individuals and personal ways to react. This is important from wellbeing point of view. We should rather challenge ourselves keeping in mind our own physiology and environment, than compare to others.

The Moodmetric daily average level is the most important

The Moodmetric smart ring measures the sympathetic nervous system reactions on a scale from 1 to 100. Counting presumes balance. When the daily average value is around 50, there is enough recovery in correlation to load. The Moodmetric ring users notice the same: the daily average is normally 45 to 55 depending on how well daily load is compensated by rest and sleep.

Levels and fluctuation during the day can be very different between two persons. Both might still feel well and with plenty of energy. If high daily figures are combined with very restful sleep, can the daily average level be the same as with a person with much lower numbers during daytime. 

Below the different persons’ consecutive day and night views, where the daily average for both arrived at 46. In this example both reached good, quite a low average, but with very different daily levels:

The daily average of the Moodmetric index is the more informative, the more the person uses the ring. It is easier to analyse own balance of load and recovery when the ring is worn also during the night.

Feedback from the Moodmetric ring users tells that own perception is in line with the measurement. If the daily average is around 50, the situation and energy levels are normal. Values over 50 for a long time go hand in hand with the feeling of overload and weakened wellbeing. Very low daily figures might indicate depression.

The Moodmetric measurement helps the user to gain balance between load and recovery. The sources of stress and ways to recover are individual. For this reason the measurement data always needs own evaluation. Categorizing and analyzing own life e.g. with the help of the Moodmetric app Diary feature is a way to more balanced life.

The complete set of 5 articles:

  1. Part 1: Fight or flight response
  2. Part 2: Chronic stress – The brain concludes that we are continuously in danger
  3. Part 3: Tools for long term and continuous stress measurement
  4. Part 4: The Moodmetric ring stress measurement and understanding the data
  5. Part 5: The Moodmetric measurement in preventive occupational health