Virtual Reality Training for Police Officers: A Comparison of Training Responses in VR and Real-life Training 3 57 Measures In this study, we assessed three main measures: physical training responses (average heart rate, maximum heart rate, activity), psychological training responses (mental effort, perceived stress), and experiences in VR (sense of presence). The specific sub-measures are described below. Physical training responses Heart rate (HR) Average and maximum heart rate (HR) in beats per minute (bpm) were recorded using a Zephyr Bioharness 3.0 device (www.zephyranywhere.com) at a recording frequency of 1 Hz. HR recordings of the active training time in the training scenarios for VR and RL were extracted and analyzed. HR Confidence (degree of validity of HR value, as a %) provided in the Zephyr output were used for data correction: data points at or below 25% HR Confidence were considered invalid and were removed from analysis (see ‘Heart Rate Confidence’, OmniSense Analysis Help, 2016). Physical inspection of extreme bpm values (outside of a realistic HR range, e.g., 0 bpm) were removed from analysis. The Zephyr Bioharness device provides valid and reliable HR measurements (Nazari et al., 2018) and is frequently used in police research (e.g., Andersen & Gustafsberg, 2016; Bertilsson et al., 2019). In police research, HR has consistently been used as a common parameter to assess police officers’ cardiovascular response to stress (Andersen & Gustafsberg, 2016; Andersen et al., 2016; Anderson et al., 2002; Anderson et al., 2019; Baldwin et al., 2019; Bertilsson et al., 2020; Vonk, 2008). Level of physical activity Level of physical activity was obtained using the Zephyr Bioharness 3.0 device (www. zephyranywhere.com). The Zephyr Bioharness contains a 3-axis accelerometer that records vertical, lateral, and sagittal acceleration magnitudes. The level of physical activity was quantified as velocity magnitude units (VMU), measured in g. VMU = where x, y, and z are the averages of the three axial acceleration magnitudes over the previous 1-second epoch, sampled at 100 Hz. A VMU of higher than .2 indicates a walking equivalent activity, and a VMU of higher than .8 indicates a running equivalent activity (OmniSense Analysis Help, 2016). Psychological training responses To assess psychological training responses, we utilized visual analogue scales (VAS) to assess mental effort and perceived stress. In police research, VAS for mental effort and perceived stress
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