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Laboratory stress study with psychosocial stress induction test on healthy individuals with varying age (younger adults vs older adults), gender (male, female), and fitness level (lower and higher VO2Max) to have a benchmark of the performance of the stress detection for the nonhealthy population undergoing the same test. Cortisol level, heart rate and subjective ratings of stress, anxiety and emotional experiences are collected as a reference.

Psychosocial stress is induced by a standardized protocol called Trier Social Stress Test (TSST[1]) during which the participant is, without prior information about the details, subjected to a simulated job interview, where he/she has, five minutes to prepare for and five minutes to give a pitch talk about why she/he would be a perfect employee in front of 3 “interviewers”. For an additional 5 minutes, the participant is required to perform a relatively difficult arithmetic task (counting backwards from 1022 in steps of 13) in the same situation, if a mistake is made the participant is required to start from the beginning. Even though the participant knows that this is a simulated event, the protocol reliably induces a stress response as measured as psychophysiological and hormonal changes. Thus, the TSST protocol provides us with a controlled and robust time-series of measurement points during which the psychological state of the participant ranges from calmness to relatively high anxiety and again relief from it. Cortisol responses and HRV as well as subjective ratings of the stress form the reference against which the Firstbeat’s algorithm is compared. In the past, the physiological responses have been shown to be very robust but subjective ratings of the situation vary a lot. We expect to see the Firtsbeat’s algorithm to 1) capture the stress responses as well as traditional HRV based measures and possibly 2) explain the subjective ratings better.

The data are gathered in three stages. First, we collect the data using young males as participants. The reason for this is that the hormonal responses are clearer in males and we can take a preliminary look at the data then. After this, the dataset is complemented with older males and finally with corresponding data from females. This order gives us some degrees of freedom in terms of the publications as their specific focus might change during the process.