There are many things that can cause stress and stress can be separated into good and bad stress. Receiving a promotion or a big bonus at work are forms of good stress, while things such as being stuck in a traffic jam or feeling ill would be bad stress. There are several ways to detect and measure stress, and the two common ways are through electrodermal activity and heart rate variability.
Electrodermal activity (EDA), more commonly known as galvanic skin response (GSR), refers to the variation in electrical properties of the skin in response to sweat secretion. The coupling of cognitive states, arousal, emotion and attention enables EDA to be used as an objective index of emotional states. Also, it can be used to explore implicit emotional responses that may occur without conscious awareness or are beyond cognitive intent.
Experimental setup and sensing sites
When the electrodermal activity method is used to detect stress by devices, a constant voltage, for example 500mV, is applied to one electrode, which leads to a current flowing through the skin to the other electrode. By measuring the voltage at the reference resistance, skin resistance can be directly determined. External noise is eliminated before the data is shown.
Heart rate variability
Heart rate variability (HRV) is one of the most robust, non-invasive measures of stress response. In the 1960s, research first linked HRV to stress when doctors realised that tests showing babies in distress before birth showed a more regular spacing between their heartbeats, compared to those who were not in distress.
While most people would think that the heart beats in a regular rhythm, this is not the case. For example, in healthy young adults, the interval between heartbeats naturally varies and ranges between 10 to 15 beats per minute. And when the person is in distress, the autonomic nervous system activates the flight-or-flight response, which reduces the variability in the interval between heartbeats.
Time domain methods
There are many ways where HRV can be measured, and the easiest approach would be the time domain method. In this case, either the heart rate at a specific point in time or the intervals between successive complexes are recorded. Other types of methods to detect and measure HRV include the spectral and geometric methods.
Increasingly, people not only care about their physical well-being, but their mental and emotional well-being as well. Although there has been much criticism on the accuracy of devices that are able to detect stress, the measurements provided still do serve as a guide to help people better understand and manage their stress levels.
American Heart Association | Heart Rate Variability
Benedek, M., & Kaernbach, C. (2010). A continuous measure of phasic electrodermal activity. Journal of Neuroscience Methods, 190(1-5), 80–91. http://doi.org/10.1016/j.jneumeth.2010.04.028
Braithwaite, J. J., Watson, D. G., Jones, R., & Rowe, M. (2013). A guide for analysing electrodermal activity (EDA) & skin conductance responses (SCRs) for psychological experiments. Psychophysiology, 49, 1017-1034.
Kappeler-Setz, C., Gravenhorst, F., Schumm, J., Arnrich, B., & Tröster, G. (2013). Towards long term monitoring of electrodermal activity in daily life. Personal and ubiquitous computing, 17(2), 261-271.
Live Science | New Trackers Claim to Measure Your Stress, But Do They Work?
Singh, M., & Prakash, N. R. (2015). Miniaturisation of Wearable Sensor for Stress Monitoring Using Electroderml Activity. International Journal of Innovative Research in Science, Engineering and Technology, 4(5), 3744-3750.
SweetWater Health Beat Healthy | Stress and Heart Rate Variability
Vollmer, M. A robust, simple and reliable measure of Heart Rate Variability using relative RR intervals.
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