Prediction of Self-Perceived Stress and Arousal Based on Electrodermal Activity – a paper by Tomppa Pakarinen, Julia Pietilä and Hannu Nieminen has been presented at the European Biomedical Conference EMBC in Berlin in July.
The researchers were keen to understand how individuals perceive stress and how devices can capture it. The need for this kind of study has been there for a long time. Today, prolonged stress is a common cause of work-related health problems and has major negative impact on employee wellbeing and productiveness. Being able to measure exposure to stress long term would provide a valuable tool for improving workplace and personal wellbeing and potentially reduce health-related problems.
In contrast to some earlier studies, the researchers in this study attempted to simulate actual work-related stress rather than induce extreme reactions.
Electrodermal activity (EDA) in evaluation of mental state
Questionnaires are commonly used to measure the individual’s subjective perception of stress. Physiological measurements are used for assessing the physiological responses related to stress and arousal. The most common measures are heart rate variability (HRV), electrodermal activity (EDA), heart rate, electroencephalography, respiration, and skin temperature. In previous research, HRV has been the most commonly used method.
Electrodermal activity (EDA) reflects the functions of the autonomic nervous system and was chosen to be applied in this study. It is often used for the evaluation of different mental states such as short and long-term stress. In the study, test subjects were exposed to a 3-phase test (relaxation, arousal, stress) during which EDA was recorded, and the self-perceived stress and arousal were assessed.
The results are promising for the use of EDA as a long-term measurement of work-related stress
In this study, the research team was able to reliably classify relaxation, arousal and stress-inducing phases of simulated work with high accuracy (94.1% with BIOPAC, 82.8% with Moodmetric smart ring), using a number of EDA features.
When comparing EDA to subjective questionnaires, the self-perceived stress and arousal were classified with much lower accuracy of 60.5–72.2%. Based on the results, it is possible that individuals are less able to recognize and interpret the level of stress they are experiencing in a particular situation than the measuring devices reading their EDA.
Overall the results are promising for the use of EDA as a long-term measurement of stress at work.
For Moodmetric the research is an important, continued validation of accuracy. The easy-to-use Moodmetric smart ring can provide information on the stressfulness of work-related situations almost as accurately as respective laboratory equipment designed to measure EDA.
There are reports in media daily about work and study-related stress, burnouts and the increase of mental load, especially among knowledge workers. The focus is on what to do when stress has already become chronic. The act of balancing between mental load and recovery is yet to become an everyday task.
There are tools for companies and occupational health to gather objective, real-time data about an individual’s cognitive and emotional stress. They comprise an efficient method for preventing the build-up of stress when applied before the load gets too high.
The tool matters
When the aim is to pay attention to mental load, the Moodmetric measurement provides just the needed data. The Moodmetric smart ring, worn as a normal ring, is a measuring device that gathers accurate information about cognitive and emotional stress, around the clock. The smartphone app shows real-time data. Measuring in real time motivates to pay attention to one’s choices affecting mental well-being every day.
Why is it important that the measuring happens in real time?
We all need feedback. The most effective is instant feedback that makes us see the cause and effect, better realizing the connection between what we did and what was the outcome.
Real-time measurement also catches our attention and encourages us to try out things that might affect the result. For example, how fast does my stress level go down if I breathe deeply for 5 minutes in front of an open window?
Let’s say a meeting lasts from 2pm to 3pm. The topic is inspiring, the participants throw in new ideas, decisions are made. A person wearing the Moodmetric ring follows her stress levels during the meeting and sees them fluctuating between 45 and a full 100. Alternatively she gives a glance at the app after the meeting. The numbers show that the stress levels were high. And because the feeling was positive, she concludes that this was a meeting inducing positive stress. She knows that recovery is important also from excitement and takes a moment to relax in a quiet space before the next meeting. The sympathetic nervous system calms down, both the body and mind get a moment of rest.
A long enough period of uninterrupted measuring, roughly two weeks, provides reliable data of the amount of mental load the person is experiencing. It contains a good number of different kinds of days, where one exceptional day does not significantly affect the big picture.
The Moodmetric measurement tells about the amount of mental load
The right metric helps to increase self-understanding and tells where the personal boundaries for high and low stress reside. Objective data, namely a clear number is a decision-making tool and a call for action: “After a day at the office, is it better for me to go jogging, or just for a walk along the scenic route?”
Measuring devices can be used continuously or periodically until the person feels that their control over the issues causing mental load has improved.
The Moodmetric measurement
The Moodmetric smart ring gives real-time information on what increases and what decreases mental load during day and night. It supports the wearer in finding the optimal balance between emotional and cognitive stress versus recovery.
A two-week Moodmetric measurement period is sufficient to provide the user with an understanding of their stress levels. If the levels are normal, the measurement can be repeated in, say, a year. If the levels are very high, it is advised to discuss with a healthcare professional about the data and make your own assessment of the load and its causes, both at and off work.
The Moodmetric smart ring is a prime example of Finnish innovation in the area of health technology. Vigofere Oy was set up as a company five years ago to commercialize the invention of Henry Rimminen, D.Sc., who had developed a smart ring which measures electrodermal activity (EDA). The ability to measure, outside of test laboratory conditions, the electricity that your body emits was revolutionary and 2013 saw the birth of the first prototype for further development.
How It All Begun
As a researcher at Aalto University, Henry Rimminen had worked on various sensors and methods for measuring physiological activity. Fitness trackers were a growing trend and devices based on measuring heart rate had been available for consumers for some time already.
Measuring electrodermal activity had been in research use for over a hundred years, but there were no practical applications of the measurement method on the market for consumers. It was this challenge that Henry Rimminen aimed to solve.
Our bodies react to external stimuli, both psychological and physical. This triggers off the sympathetic nervous system, the activity of which can be measured by how the eccrine (very tiny) sweat glands respond. These glands are dense on the palm of our hands, making them the optimum location to place the measuring sensor on.
EDA, or skin conductance, is a phenomenon which was discovered by two researchers, Charles Vigoroux and Richard Féré in the late 19th century. The name of the company, Vigofere Oy, was derived from the names of these two trailblazers.
In laboratory conditions EDA is measured by placing electrodes on the skin, usually on the tip of two fingers. For an accurate reading, no movement is allowed.
To develop a consumer product, Henry Rimminen had to overcome several challenges:
• Downsizing the measuring device from the size of a block of cheese to as small as possible.
• Instead of restricting the use of two fingers, the device had to be effortless to wear in everyday life.
• The results should not be affected by physical movement.
• Data transfer should be wireless.
In the autumn of 2015 the first commercial version of the Moodmetric smart ring was launched. It was the result of many iterative rounds of research and development. Once the electronics and measuring capability were deemed robust enough, designer Vesa Nilsson provided the ring its Scandinavian look and feel. Vesa Nilsson is famous for transformational and clean design. For further information, see Oz Jewel.
One of the key principles Henry Rimminen followed right from the start was ease of use: It was imperative that the data the ring collects could be effortlessly retrieved, read and managed. Developing an application running on a smart phone was the next logical step.
The mobile application had to incorporate two basic elements:
• The index with the numeric values 1-100 is calculated from the raw data and show the alertness level of the person wearing the ring. High numeric figures signify stress or excitement, low figures a sense of calm.
• A round diagram demonstrates the fluctuation of the stress levels during 12-hour intervals. The use of colour make it easy to visualize, in one glance, the different levels of alertness, sliding from red for high levels on the outer peripheral of the diagram to the light greens of low stress levels on the inner circle of the diagram. For further information on the Moodmetric index and data interpretation, see here.
Vigofere Oy/Moodmetric today
Vigofere Oy has been in business for over five years and has a fully Finnish ownership. R&D is all done in Finland, as is the assembly and packing of the product too.
Moodmetric serves consumers, researchers, companies and health professionals globally.
The Moodmetric smart ring can be purchased from the Moodmetric webshop and the mobile application can be downloaded for free from the App Store and Google Play.
For companies and health professionals Moodmetric provides a measuring service for preventive stress management. Research institutes have been the first to utilize the technology and the ring in their work. For further information see our research page.
Stress is a positive thing, when it is well balanced. Our mission at Moodmetric is to help each and everyone to find their individual and optimum way to manage stress in all situations. Our goal is to significantly reduce the negative effects of chronic stress on individual, organizational and societal levels.
We at Moodmetric believe that the world can be saved from a state of chronic stress with Finnish health technology.
The Moodmetric measurement gives accurate and real time data on cognitive and emotional load of an individual. Use cases below give a snapshot on what kind of research it can be applied to. These are just a handful of examples. Electrodermal activity is a signal with great and for most unused potential in field research.
Stress measurement with Moodmetric
Positive stress is a good thing and when in control, it takes us forward. Chronic stress reduces productivity, creativity and job satisfaction and it is a risk for physical and psychological health. It is not easy to catch signals early and stress might not be detected before it has reached harmful levels.
Questionnaires are subjective and bound to a certain moment. Preventive stress management needs continuous and long term measurement. The Moodmetric ring is intended for weeks and months of use. The mobile app offers a real time view which enables insights that can be actioned immediately.
Even though the Moodmetric measurement is primarily intended for use at occupational health, the real time measurement enables several kinds of research. Below are some example use cases to give a picture of it´s possibilities:
A customer is testing a new shopping center virtually. The center is equipped with innovative implementations, including parking, navigating inside the center, paying in the shops (only mobile payment) etc. The pilot customers´ opinion have a major significance on the final drawings and the pilot is heavily studied. The Moodmetric measurement shows instantly and in real time the pain points – when the experience is getting from smooth to troublesome. The Moodmetric levels increase in seconds when the customer is perplexed.
A much simpler example would be e.g. driving through a car washing lane. How many of the customers actually get terrified inside, with not way of getting out in the middle? Could this be eased out somehow?
The Moodmetric measurement can be used to tracking stress levels in any environment, inside or out in the woods. It suits to observing a person in different situations, like choosing clothes. Which print makes the person react?
Mobile and desktop games can be extremely agitating. Chasing, fighting, racing and performing dangerous tasks is enervating. The sympathetic nervous system of the player is active, as the body does not understand that the threat is just an illusion created by the game developer.
A game can also be soothing, like puzzles. Focus is needed but vigilance not.
What kind of a game is yours and what is the target audience? What if you could design games that really calm down the sympathetic nervous system – a game that you could wholeheartedly recommend e.g. for kids with concentration difficulties?
Pay attention! – Study focus with Moodmetric
We make better decisions, our movements are correct and precise, and we make better analysis when we pay attention. Really pay attention by not letting noises, lights, phone, emails or the smell of lunch distract us.
The Moodmetric index of 1 to 100 tells our arousal level. When focused, the level is below 30, in most cases below 20. Full focus on the task at hand might show a steady level of 12 with almost a straight electrodermal activity curve on the Moodmetric mobile app. The person is far from being sleepy (although in the evening at the sofa the numbers might be exactly the same), but fully focused.
This does not necessarily need an isolated environment. Most people can find their way to reach focus no matter the surroundings. But as it is not easy, many companies design spaces and areas inside their offices that enhance concentration.
What kind of training methods provide the best results? The Moodmetric measurement makes it possible to better understand what level of focus the athlete reaches. Interventions such as mental exercises can tested and found out the ones with the best results for improving concentration. The measurement also provides insights as to when recovery from practice is sufficient. The app diary helps to analyse which activities should be toned down or avoided in order to benefit optimally from training.
Interested to know more about the Moodmetric measurement and why the Moodmetric ring is especially well suited to measure electrodermal activity?
Read our recently published articles starting with:
Stress is a good thing, it is a driving force keeping us active and productive. However, excessive strain can lead to overload, especially when the issues causing stress are beyond our control. Chronic stress is a state where stress outweighs recovery. The autonomic nervous system is off balance and the body is continuously in a state of alarm.
There is a clear link between chronic stress and several physical and psychological illnesses. Stress is often the underlying reason for burnout. Overload is difficult to recognize because it builds up over a long period of time. Stress, the feeling of not being able to cope, can still be a taboo, resulting in people seeking help too late. According to research, even 60-80% of visits to the doctor have a connection with stress (Nerurkar et al. 2013). Every fourth employee suffers from work-related stress at some point of their working life.
In this fifth part of our article series we discuss the Moodmetric measurement benefits at preventive occupational health care.
Electrodermal activity and stress
The Moodmetric smart ring is one of the first devices on the market to measure easily and reliably long-term stress by interpreting the phenomenon of electrodermal activity. This physiological measurement can accurately tell about the fluctuating stress levels of an individual in everyday life. Electrodermal activity is especially sensitive to changes in emotional and cognitive stress and being able to measure it accurately in a particular context tells us what causes stress and why. This makes the Moodmetric smart ring a great tool for managing stress, especially for knowledge workers.
The Moodmetric smart ring is easy to use and the measurement results can be observed in real time on a mobile app. For a good overview, it is recommended that the ring is worn for at least a period of two weeks, but using the ring and its data can be well incorporated into everyday life, for as long as it is needed. In two weeks, however, the user learns about their individual sources of stress and recovery, and gains motivation to seek a better balance between the two.
The Moodmetric measurement is real-time, informative and accurate, with the ring being easy and comfortable to use. The data is represented in visual form on a mobile app and the real-time view enables immediate actions. This is very important when aiming for behavioral changes. Corrective actions can be applied into practice right away.
According to customer feedback, the data accumulated by the Moodmetric smart ring helps to better recognize individual sources of stress and recovery and motivates one to take concrete actions.
Moodmetric provides new services for preventive occupational health care
The Moodmetric reseach and development has been strongly guided by our customer feedback. Customer comments and use cases have been collected since 2015. Especially our corporate customers have repeatedly expressed their wish to have the Moodmetric services available at occupational health care. Individuals often look forward to receiving professional help in interpreting the data, along with gaining a better understanding of good practices in managing their stress.
Occupational health care has a limited selection of tools to offer customers seeking help in managing their stress overload, or whose health issues are clearly stress related. Most customers at occupational health care might just need a guiding hand and not long-term consultancy, but they would still like to have aids such as Moodmetric at their disposal if needed. It is in the interest of insurance companies too to see a more varied selection of preventive healthcare solutions being introduced and available for patients.
Well-being technology can motivate individuals to take an active role in enhancing their own health. The Moodmetric mission is to prevent health issues and related costs caused by stress, all the way from individuals to businesses and communities alike.
The Moodmetric stress measurement data is real-time and tells of the fluctuating stress levels also in long term.
This series of articles is about stress and the 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 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 a set of electrodes. The band consists of two silver coated steel rings and an insulator band in between them.
To achieve a good and steady reading, the electrodes need be in contact with an area of the skin where the eccrine sweat gland density is high. This density can vary from 400/cm2 on the palm of the hand to about 80/cm2 on the upper arm. The ring form was chosen to achieve the best possible accuracy generated by the Moodmetric sensor. The actual point of measurement is on the inside 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 turned on or open, nor the phone near the ring. When the app is activated and the calendar icon chosen, the ring sends the data to the app via a bluetooth connection. The measuring and data storing to the ring continue immediately. The real-time signal – in other words, the ongoing measuring in process – can be observed at any time on the app.
The Moodmetric signal is the violet curve on the mobile app that can be observed in real time. It is the raw measurement signal, autoscaled in order to have the whole amplitude visible even during strong reactions.
The curve enables the analysis of single reactions. Even a thought – excitement, idea, awe – can cause a peak and is registered with only a 1-2 second physiological delay.
Interpreting the raw signal requires expertise in the measurement method and understanding of the possible sources of error.
The Moodmetric stress measurement data
The raw signal for electrodermal activity (EDA) is difficult to interpret. Strong reactions can easily be spotted on the curve, but mathematical methods are needed to gain further insight.
The Moodmetric level has been developed to provide accurate EDA measurement data that is easy to interpret. The algorithms count an index from 1 to 100 so that 1 is the lowest the person can reach. This is possible, for example, in deep sleep. 100 is the maximum level of arousal, strongest possible reaction. Since we are all individuals, the Moodmetric measurement method is designed to find the minimum and maximum levels of each person within the first 12 hours of taking the ring into use. This is called the calibration period. The ring should be recalibrated when handing it over to another user.
The MM level on the app, both the numeric value and the curve being drawn, show the person’s ongoing activity and level of excitement for the past few minutes. The MM level does not indicate single reactions, but changes fast if the arousal level of the person increases or decreases rapidly. Increasing is first visible in the growing amplitude and the raising trend of the Moodmetric curve, then in the higher numeric value for the MM level.
It is easy to get to 100. The challenge lies in working out the ways in which to get the MM level as low as possible.
When calculating the MM level, the algorithms minimize the effect of finger movement and skin moisture. The MM level is comparable between users. If two persons are placed in the same environment and situation, it is possible to observe which one is calmer.
There is no momentary optimal value
It is normal for the Moodmetric level to fluctuate between 1 and 100 during the day. No momentary value is good or bad.
It is equally important to acknowledge that the Moodmetric measurement does not tell whether a reaction is positive or negative. The Moodmetric ring is not a detector of emotions as such.
The fluctuation of stress levels is different for everyone
There are people who react fast and strong, while others respond more calmly. For instance, creative people are often very susceptible to stimuli, which can translate into high and fluctuating MM levels. In contrast, a person doing work that requires much concentration over long periods of time might have low MM levels throughout the working day.
The levels can be high due to excitement and energy, or low due to intense concentration. 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. For an accurate assessment, the measurement data always needs to be complemented with the ring wearer´s own perception of the situation. Only the person in question knows whether a set 100 tells about excitement or irritation.
A successful team is heterogeneous also by the way they react
On average, it is productive at work to have people of different temperaments. Depending on the work, of course, a team consisting only of individuals with either a very mild or a very strong natural way of reacting is probably not as productive as a more heterogeneous team.
The Moodmetric stress measurement data increases our understanding of the different ways in which people react to various situations. This is important from the point of view of health and well-being; to challenge and grow, we should look within and learn from our experiences rather than compare ourselves to others.
The 24-hour MM average level is what it’s all about
The Moodmetric smart ring measures the reactions of the sympathetic nervous system on a scale of 1 to 100. When the 24-hour average value is around 50, there is enough recovery in correlation to the load.
Fluctuation of the MM levels during the day can vary much between different individuals. High daily figures are no cause for worry if the person feels energetic enough and has a restful night: It is the 24-hour MM average level that counts. The same goes for someone whose MM levels don’t peak during the day.
The point is demonstrated in the graphs below: Two persons have exactly the same 24-hour MM average level of 46, which signifies a good balance between rest and activity, but their autonomous nervous systems are activated in different ways and by different stimuli during night and day.
The more you use the ring, the more information you gather to help you adjust your behavior. It is therefore recommended that the ring is worn also during nighttime.
Feedback from users of the Moodmetric ring indicate that the MM level correlates with a user’s own perception of their situation. If the 24-hour average is around 50, the energy levels are normal. Values over 50 for long periods of time go hand in hand with the feeling of being overloaded; cracks in one’s well-being begin to show. Very low daily figures, on the other hand, might be a sign of depression.
The Moodmetric measurement helps the user to gain balance between load and recovery. The sources of stress and ways to recover differ from person to person. For this reason, the measurement data should never be examined in isolation, but further self-assessment by the individual is required. The Moodmetric ring and app are tools for a person seeking more balance in their life.
The complete set of 5 articles explains the Moodmetric measurement, science behind and the applications:
Stress can be measured in several ways in clinical setting. The measurements done in laboratory give versatile and accurate information. But as we do not live in a laboratory, they can not interpret the changes in our daily lives. Researchers and individuals need tools for long term and continuous stress measurement.
For decades there has been reliable methods available to measure stress in laboratory setting. These methods include heart and heart rate variability measurement performed with several accurate sensors. Other heart related tests are blood flow measurements with long term registration of electrocardiography and blood pressure. Additionally there are tests on the autonomic nervous system and biochemical tests. The biochemical tests include hormonal and immunological definitions of blood, saliva and urine.
While servicing hospitals and research laboratories, these methods can not give a full picture on person´s stress level. Chronic stress develops over a long period of time and recovery can take weeks and months. User friendly methods that fit to daily life are needed to measure stress in long term.
Non-intrusive wearable devices are the solution for long term measurements
People are not willing to make huge compromises when it comes to health and wellbeing interventions. Activity trackers and other wellbeing devices have brought everyone the possibility to understand own physiology. Some of these equipment also draw conclusions on the stress level of the user.
Physiological measurement methods to follow stress levels for weeks or months are not yet available for clinical use. At the moment continuous and long term stress measurement can be done by measuring heart rate variability or electrodermal activity.
Heart rate variability (HRV)
A healthy heart is not a metronome. Heart rate variability means the variation between consecutive heart beats. At rest the variation can be from a few tens upto a hundred millisecons.
Why the heart rate varies
Heart rate variability is a way for our body to regulate optimal blood flow to the brain. The more variation there is between the beats, the bigger the activity of the parasympathetic system. This means that the recovery functions of the body work well.
When action is needed the rest-and-digest functions of the body are shut off. Heart rate variability gets smaller for instance during the fight or flight response that activates the sympathetic nervous system. The heart pounds with regular beats. This is because in a fight the purpose is to stay alive and not fine tune bodily functions.
Factors affecting HRV
The heart rate variability is affected mostly by age, gender and pulse. The higher the age and the resting heart rate, the smaller the variation. Additional factors are physical and mental stress, smoking, alcohol and coffee, overweight, blood pressure and glucose level, infectious agents and depression. Also the inherited genes affect the heart rate variability significantly. Individual variation is large and therefore there are no clear set limits. During measurements it is important to pay attention to rest and physical load. When the heart rate goes up due to physical strain, the heart rate variability decreases.
Counting heart rate variability and accuracy of measurement
Heart rate variability as a phenomenon is known since 1960’s and applied in health care for a long time. The most accurate way for measurement is the electrocardiography (ECG or EKG). For wellbeing uses there are several devices available, out of which most accurate are those measuring from chest. Wrist and finger measurements suffer in accuracy especially with high heart rates due to movement of the measured spot.
Heart rate variability is measured by calculating the time interval between heartbeats. This is normally done by looking at the R spikes on an electrocardiogram, the R-R interval. Mathematical methods are needed in the analysis of the heart rate variability. With advanced algorithms it is possible make deductions about a person´s physical and mental load.
Heart rate variability is high at rest, when the person is young and healthy and with a good physical condition. Low HRV might indicate stress for a healthy adult.
A physiological phenomenon known since over hundred years is electrodermal activity. Psychological factors affecting the conductance of skin was found almost simultaneously by a French neuroscientist Féré (1888) and a Russian physiologist Tarchanoff (1889). The first observations had been done already over ten years prior by a French threrapist Vigouroux. Out of several naming conventions for the phenomenon the electrodermal activity (EDA) prevailed.
Electrodermal activity from physiological point of view
The skin becomes a better conductor of electricity when the eccrine sweat glands process sweat to skin surface. Eccrine glands are innervated by the sympathetic nervous system and are part of the fight or flight response system. This makes electrodermal activity (EDA) important from stress measurement point of view. The major reason for it’s importance lies in the fact that EDA is solely mediated by the sympathetic branch of the autonomic nervous system, thus being not subjected to parasympathetic inﬂuences as most of the other autonomic measures (1).
There has been equipment available for laboratory level EDA measurement since founding of the phenomenon. Usually the measurement is done from palms or fingers with electrodes that are connected to an amplifier.
An unprocessed EDA signal is very sensitive to movement, so in most test settings the subject is requested to stay still. In the past this has limited the EDA measurement mainly to laboratory.
Lately the wearable technology development has made improvements also to EDA studies. Advanced algorithms and signal processing have made it possible to compensate the movement artifacts, and wearable sensors have been brought to market.
Measuring EDA as a continuous long-term measurement in a non-intrusive way is desirable for many different ﬁelds of research and diagnostics (2). Studies in psychology and behavioral sciences benefit when the measurements can be done in normal daily life, outside laboratory. Additional advantage is that wearable technology enable research with moderate equipment cost.
Measurement units, parameters and accuracy
EDA measurement registers the inverse of the electrical resistance ‘ohm’ between two points on the skin – i.e., the conductivity ‘siemens’ of the skin in that location (3). The recorded EDA signal has two components. The slowly varying tonic component of the EDA signal represents the current skin conductance level (SCL). The skin conductance response (SCR) corresponds to sympathetic arousal (1). It is a spike-like component whose amplitude and frequency indicate of the person´s activation level. EDA does not tell whether the person is experiencing something positive or negative. Raise in activation level can be due to any strong emotion such as excitement, joy, fear and anger.
The accuracy of the measurement depends on the equipment used, stability of the environment and the point of measurement. The preferred sites for EDA measurements are located in the palms of the hands and the soles of the feet (4). Age and gender affect EDA somewhat. External temperature and movements of the person have an effect on the measurement signal that needs processing to draw the right conclusions.
EDA measurement can be very accurate also in wearable form. Field studies with these devices are possible already today.
Applications of EDA
Electrodermal activity has a lot of clinical and practical applications, with polygraph one of the most well known. In psychological research the phenomenon has been applied since it was first found. Later the uses have been across many fields e.g. gaming and user experience, marketing research and in top sports.
The next article in this series tells how the Moodmetric ring measures electrodermal activity
Different kinds of physiological measurement systems have been used for a long time in top sports. Wearable devices have made exercise tracking easy for everyone.
Heart rate monitoring is the most used measurement in sports. It was developed by an Australian physician Robert Treffene for swim exercising. In Finland hear rate monitor was invented by the Polar Electro founder, professor Seppo Säynäjäkangas in 1975.
Today there is a huge variety of equipment for hear rate monitoring. The most accurate ones still measure from chest, either with a band or with taped sensors. Wrist worn trackers are comfortable to wear and they have largely displaced chest bands especially with non-professional exercisers. The accuracy of wrist worn trackers has been improved in past years, but it suffers especially at high heart rates.
Heart rate, heart rate variability (HRV) and electrodermal activity (EDA)
Analysing heart rate gives a good view of physical strain. With different algorithms it is possible to understands also recovery, sleep and stress.
Heart rate variability (HRV) has been lately brought up especially in measuring non-physical load. There are challenges, as at high heart rates the algorithms struggle to understand what happens: is the person physically at rest, but nervous (e.g. about a soon-to-start exam), or is it now about physical exercise? Here the accelerometers, present in all of the trackers, are of help. These components can detect whether a person is moving or is at rest, and much more about movement directions and pace.
The electrodermal activity (EDA) measurement brings interesting new information to analyse performance of an athlete. This does not tell about heart, but about sympathetic nervous system activation through sweat gland reactions of skin. Skin is the only organ that is purely innervated by the sympathetic nervous system. The EDA measurement is very sensitive to emotional and cognitive stress, and it has been used in psychological research already for over 100 years. Only lately it has become available for consumers.
The Moodmetric smart ring measures electrodermal activity. The ring is comfortable to wear and it is thus well suited for continuous, long term measurement. Only a sufficiently long measurement period gives a full picture on stress, how it is generated and how recovery happens during weeks, months and even years.
Both top sports, and going after personal goals in exercising benefit of stress load related information. It is good to understand what sources of stress or recovery might affect the performance. For instance, cognitive load of a professional athlete might be less than for someone who need to have a day job to finance the sports career. The professional athlete can probably exercise more, as there is more time for recovery. The results and performance are affected by emotional and cognitive load, if there is no time to unwind.