2.2.3.1 Reactive stress tolerance test. Reactive stress tolerance is measured by
means of the Determination Test, which is a Vienna Test System-based test, a computerized platform of psychodiagnostics manufactured by Schuhfried GmbH (Schuhfried GmbH, 1996). The test requires that the respondent use their cognitive ability to distinguish different sounds, colours, and memorize relevant characteristics of stimulus configurations; the difficulty in this test is that the client is asked to respond to rapidly changing visual and acoustic stimuli in the way instructed during the practice phase of the test. The client responds to the relevant incoming stimuli by pressing one of the five round coloured buttons, with each of them corresponding to a visual stimulus displayed on the screen, or one of two rectangular coloured buttons, with each of them corresponding to a different pitch of an acoustic stimulus, or one of two foot pedals (i.e. right or left), with each of them corresponding to a white rectangular visually distinct field in the bottom left - and right- corners of the screen respectively. This specific test form is the adaptive mode, which allows the system to always follow the speed of the respondent. As a result of this, a different total number of stimuli may
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be generated within the 4 minutes of the test, for each respondent. To control for the different number of stimuli generated in different test administrations, the total number of correct responses and the total number of wrong responses (i.e. incorrect plus omitted responses) have been divided by the total number of stimuli generated in each administration, which results in the two ratios used as reactive stress tolerance indices in the statistical analyses.
The total duration of the instruction/practice phase and the test itself is approximately 6 minutes (i.e. approximately 2 minutes for the instruction/practice phase and 4 minutes for the test).
2.2.3.2 Mindroom testing and training. The ‘mindroom’ is an ASPIRE laboratory
used for integrated psychophysiological testing and training within a standardized environment. The ASPIRE mindroom is a four-station mindroom, with each of the stations consisting of an armchair, an audio headset, a laptop with biofeedback software installed in it, a biofeedback/neurofeedback encoder and sensors. The mindroom has a client area, where all the stations are placed, and a control room, divided from the client area by means of a glass partition; in the control room,
practitioners can view the graphs and statistics of each session but, also, they can have full control of the clients’ laptops. The audio headsets installed at each mindroom station allow practitioners to communicate with any of the clients using a microphone installed in the control room.
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The manufacturer of the biofeedback hardware and software used in this study is Thought Technology Ltd, which is based in Montreal/ Canada. The specifications of the hardware are explained below:
ProComp Infiniti encoder. This is an 8-channel, multi-modality encoder which is
used for real-time computerized biofeedback and neurofeedback as well as data acquisition. The encoder is connected to a fiber optic cable which, in turn, is connected to the client’s laptop by means of a USB module (ProComp Infiniti Manual, 2017).
Blood volume pulse (BVP) sensor. This is the sensor used for measuring/
monitoring heart rate in this study. Measurement with this sensor is based on
photoplethysmography; the sensor, actually, monitors the change of the reflected light caused by blood flow. Each heartbeat results in more red light being reflected, which is recorded by the sensor, whereas less red light is reflected between pulses (Thought Technology Ltd., 2003). During this study, the BVP sensor was placed on the palmar surface of the non-dominant index fingertip of the clients. The type of BVP sensor used was BVP-Flex/ Pro. In this project, the BVP sensor was placed on the clients’ non- dominant index finger.
Respiration sensor (RESP). A respiration sensor was used for monitoring the
pace and pattern of abdominal respiration of the clients. This sensor has a velcro strap which is stretched around the client’s abdomen and, actually, transforms the
expansion or contraction of the abdominal area of the client to a rise or fall of the wave being displayed on the screen. The respiration sensor is placed slightly above the naval
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area of the client. The type of respiration sensor used in this study was RESP- Flex/Pro (Physiology suite manual, v. 5.1).
Skin conductance sensor (SC). This is a sensor used to monitor conductance
across the skin and has two fingerband electrodes which, in this project, were attached to the middle and small finger of the participants. Skin conductance is, actually, the ability of the skin to conduct electricity; real-time variations in conductance reflects activity of the sympathetic nervous system and are related to levels of stress. A relaxed state usually gives a conductance of approximately 2 μS (i.e. micro-Siemens), however, this varies according to the skin type of the client as well as environmental factors. The sensor used was the Skin Conductance Sensor- SA9309M, by Thought Technology Ltd. (Thought Technology’s sensors and accessories manual, SA7511 Rev.4).
Skin temperature sensor (TEMP). This is, actually, a thermistor measuring
surface temperature on the skin and, in this project, was placed on the non-dominant ring finger of the participants. The role of this sensor is to identify changes in the temperature of the client’s hand as this reflects increased or decreased blood flow to the extremities which result from vasodilation or vasoconstriction respectively. The skin temperature sensor used was the Temperature Sensor-SA9310, manufactured by Thought Technology Ltd. (Thought Technology’s sensors and accessories manual, SA7511 Rev.4).
EMG (electromyography) sensors. Surface electromyography (SEMG) was used,
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and right trapezius) which results from muscle contraction when an individual is stressed. For this project, MyoScan-Pro (SA9401M) EMG sensors, manufactured by Thought Technology Ltd., were used. (Thought Technology’s basics of surface electromyography, 2008).
Furthermore, all of these sensors were connected to different channels of the above-mentioned encoder.
Biograph Infiniti version 6.0.4. This is the main psychophysiology software on
which the resonant breathing frequency assessment as well as the HRV training sessions were based. Biograph Infiniti has been designed and manufactured by Thought Technology Ltd. The first version of it was available in the market in 2003 whereas the version used for the present study was designed and distributed in 2014. Furthermore, the HRV training sessions were conducted using Thought Technology’s Physiology Suite, which acts as a plug-in software within Biograph Infiniti, and, specifically, with its pre-designed screen labelled ‘HRV-% power, pacer & animation’. Resonant breathing frequency was assessed by means of another software which acts as a plug-in to the Biograph Infiniti as well and has been created by Inna Khazan (2013) in collaboration with the Biofeedback Federation of Europe (BFE).