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How NOWATCH measures your stress levels with Biosensing

7 min read

How NOWATCH measures your stress levels with Biosensing

Do you ever feel very stressed or overwhelmed? Do you wish to manage your stress? With your NOWATCH wearable you can take control of your stress levels through a novel Biosensing Technology developed by Philips.

This technology measures your stress levels and predicts an overstimulated brain enabling you to take action before this happens. Read how this works in the article below.

At NOWATCH we want to provide trustworthy information about your health and wellbeing. That is why we write our articles based on scientific papers. However, the information is not intended as medical or professional advice. 

Skin conductance

Skin conductance technology is based upon the physiological effects of stress on the sweat glands. These sweat glands are controlled by the sympathetic nervous system. When the sympathetic nervous system is active due to stress, eccrine sweat glands, located throughout the whole body and specifically on the palms of your hands and soles of your feet, will produce more sweat. Sweat produced by eccrine glands consists of water and electrolytes which have conducting effects on the skin. 


Sweatblock 2018Machado-Moreira CATaylor NAS: Psycho- logical sweating from glabrous and nongla- brous skin surfaces under thermoneutral con- ditions. Psychophysiology 2011;49:369–374 HarkerM. (2013). Psychological Sweating: A Systematic Review Focused on Aetiology and Cutaneous Response. Skin Pharmacology and Physiology26(2)92–100.doi:10.1159/000346930

Biosensing Technology

The skin conductance sensor, called Biosensing technology, in the NOWATCH is developed by Philips. This technology uses an EDA-sensor, short for electrodermal activity sensor, to measure the different levels of skin conductance. The Biosensing technology sends a small non-harmful current to the skin and measures the change in electrical conductance between two points over time on the skin. Skin conductance provides information on the skin’s sweat properties which relates to the activity of the sympathetic nervous system. 

Skin conductance reflects sympathetic activity and stress levels

Stress results in activation of the sympathetic nervous system which has an immediate impact on eccrine sweat glands. Sweat glands are the only organs that are directly coupled to stress through acetylcholine, as they are solely controlled by the sympathetic nervous system. Other organs are coupled to both the sympathetic and parasympathetic nervous system. This is why sweat glands are a clear indicator of sympathetic activity in response to stress.

All responses are mediated by adrenaline and noradrenaline, except sweating which is triggered by acetylcholine release.

In a stressful situation, sympathetic activity increases, and eccrine sweat glands are activated. These sweat glands produce more sweat leading to higher skin conductance levels. The relationship between skin conductance and psychological stress is strongest at specific body locations: fingers, palms, feet, and shoulders. 


EDADeriving a Cortisol-Related Stress Indicator From Wearable Skin Conductance Measurements: Quantitative Model & Experimental Validation. Front. Comput. Sci. 2020 Van Dooren Mde Vries GJJanssen JH. Emotional sweating across the body: comparing 16 different skin conductance measurement locations. Physiology & Behavior. 2012;106(2):298-304

Cognitive zones and cortisol levels

Cortisol and skin conductance are both direct results of the same stressor and are thus related. In reaction to a stressor, skin conductance reacts immediately while effects of cortisol occur 25-60 minutes later. Because of the different time frames, skin conductance is a predictor of cortisol levels. Cortisol levels can reflect mental states and is an interesting parameter to continuously monitor. To obtain accurate cortisol measures, you will need blood, saliva, or hair samples. Skin conductance is a good way to measure and predict cortisol levels. 

NOWATCH and Philips developed prediction algorithms to determine mental states up to 60 minutes in advance to manage stress before the brain gets overwhelmed and overstimulated.

The mental states are categorized into three cognitive zones:

  • Overstimulated: the body shows signs of stress and the user might need a break, go to bed early, or mediate.

  • Balanced: the body is in a balanced mental state, no changes are required.

  • Understimulated: the body shows low physical stress and the user might consider exercise or taking on a new project

Through Biosensing Technology, NOWATCH can provide you with tactile signals when it predicts over- or under-stimulated cognitive zones. This feedback gives the user the chance to change his or her behavior and cultivate a bigger sense of ease and balance over time.

Trends of these cognitive zones show how the user’s body responds to stress and how different actions impact his or her stress levels. This provides insights into the understanding of stressors in daily life and how to manage them.

Natoewal, Philips:The cortisol peak follows 20-30 minutes after the stressor occurred. You cannot prevent this, as the stressor already occurred. What we can do is predict that if you continue to do what you’ve been doing in the last half hour, then you will be overstimulated one or two hours from now. The prediction gives an opportunity to deflect that trend. Basically, to take a break and go for some relaxation activities to prevent becoming overstimulated (Medgadget, 2020).


Muriël v. Oers

Science Writer @NOWATCH

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