Improving Work Safety. That is our goal we are striving to reach together with one of the world‘s leading risk management organisations. The employees need to frequently switch their working location from full conditioned office rooms at 18° C to outdoor locations in direct sunlight in the United Arab Emirates, with temperatures up to 40° C. These conditions are contributing to a physically and mentally stressful work day. People working in such conditions need a strong adaptive capacity. Cosinuss° is now helping these employees to monitor their level of Fatigue and Physical Stress Index in order to prevent possible serious accidents and long term harm. In our corporate pilot study we are validating how cosinuss° wearables and analytics can be used in this demanding setting and how accurately parameters like the Fatigue Score and Physiological Strain Index (PSI) can be monitored during work. This evaluation study has a high importance because in the long run, a monitoring routine will reduce the risk of dangerous situations caused by a state of exhaustion.


For this study, ten selected employees were equipped with the cosinuss° One in-ear sensor and the cosinuss° LabApp on their smartphone. They monitored their heart rate, heart rate variability (RR-intervalls) and body temperature continuously during an average working day focusing on the usability, especially during location changes. The data was automatically transmitted from their smartphones to a pseudonymised account on the cosinuss° cloud server and then further analyzed. Using the heart rate and body temperatur  values the unique algorithms calculated the Physiological Strain Index (PSI). Additionally, the heart rate variability (HRV) was calculated as well and used to generate a fatigue score. A continuous tracking of these parameters during a whole day generates a database from which signs of low physical and mental working ability can be recorded and in future even prevented.

  • Improve work safety

  • Monitor signs of fatigue at changing temperature conditions

Pilot Study Requests

Usability of cosinuss° wearables

  • How well can users handle the in-ear wearables while being at work?
  • How reliable and of which quality is the incoming data?

Work Safety improvement

  • What is the variety of the fatigue score during the day?
  • Is there a correlation between the fatigue score and the workspace temperature?
  • Is there a correlation between the Physiological Strain Index (PSI) and the workspace temperature?


The duration of the pilot study has been 4 weeks. During this time, ten selected employees of the risk management organization had to wear the cosinuss° in-ear sensor during their regular working day. During they work employees were frequently switching location between conditioned offices and hot outdoor locations. Additionally to the monitored data, the on-spot temperature at each location was separately tracked.

The cosinuss° One wearable monitored:

  • Heart Rate (bpm)
  • Heart Rate Variability / RR Intervals (ms)
  • Body Temperature (°C)

The cosinuss° server analyzed:

  • Physiological Strain Index (PSI).
    An indicator for heat stress based on the heart rate and body temperature. Using a range from 0 (no heat stress) to 10 (extreme heat stress)
  • Fatigue Score
    An indicator for reduced mental and physical performance capability based on the Heart Rate Variability. Using a range from 1 (fully alert) to 7 (completely exhausted)

The cosinuss° usability indicators:

  • The signal quality (%) indicates how well the wearable fits in the user‘s ear
  • Measurement intervals of 30 minutes to optimize amount of data



80% of the tracked data had a signal quality from good to excellent. Meaning the cosinuss° One can monitor the vital signs of first-time untrained users reliably during regular work. The reason for the other 20% with a quality from moderate to bad were mostly the wrong placement of the sensor inside the ear or a bad Bluetooth connection between smartphone and the in-ear sensor.

The transmission between the cosinuss° One sensors and the personal smartphone of the employees worked excellent in general. 90% of all data transmissions were completed successfully. Only one test person had known issues with his smartphone model to keep a steady connection via Bluetooth Low Energy.

Fatigue Score

It is noticeable that the fatigue score is subject to fluctuations during the day. As expected, it indicates a high performance level at the beginning of the day and a reduced performance level at the end of the day. Furthermore, there is a noticeable correlation between the fatigue score and the location temperature. The average fatigue is decreasing with the decreasing of the location temperature.


The Physical Stress Index, too, is subject to fluctuations during the day, however this score could not indicate extreme conditions during our study. The highest PSI value measured in this pilot was at score 5 with 7 being the highest. Two test persons in the study had shown a strong correlation between their PSI and their location temperature. Their average PSI was decreasing with the decreasing of the location temperature.


We were able to answer the initial questions of this pilot study. The cosinuss° One is a convenient way to track the progress of the fatigue score and the physiological strain index (PSI). A correlation between the location temperature and various vital signs was apparent and can be plotted in the graphs. The employees of the risk management organization were motivated and did handle the cosinuss° wearable very well without any training or detailed instructions.

In a second study, we want to realize a system to notify the user in real-time about his/her current state of stress. Also, there should be a project dashboard where users can access their data and results, seeing their scores graphically displayed. This will make the data of the various measurements more accessible, more readable and more understandable for each participant. The employees can thus interfere directly with their behavior and prevention guidelines to improve their work safety and personal comfort at any time.