Chapter 4 82 Dependent variables Physical training responses Heart rate 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 analysed. HR Confidence (degree of validity of HR value, as a %) provided in the Zephyr output was 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). Bpm values outside of a realistic HR range (e.g. 0 bpm, values > 220 bpm) were removed from analysis through inspection of the data. 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., 2019; Anderson et al., 2002; Baldwin et al., 2019; Bertilsson et al., 2019; Vonk, 2008). Psychological training responses To assess psychological training responses, we utilised visual analogue scales (VAS) to assess mental effort and perceived stress. In police research, VAS for mental effort and perceived stress (originally anxiety) have been frequently used to quantify self-perceived psychophysiological responses to training and complex police tasks (e.g. Giessing et al., 2019; Nieuwenhuys et al., 2009; Oudejans, 2008; Wilson et al., 2007). Mental effort Subjective ratings of mental effort were obtained using the VAS ‘Rating Scale for Mental Effort’ (RSME; Zijlstra, 1993) at the end of the RL and VR training (once after all VR scenarios were completed). The RSME was assessed on a VAS from 1 to 150. According to (Zijlstra, 1993), the RSME has adequate test-retest reliability with correlation coefficients between 0.78 in work settings and 0.88 in laboratory settings. Perceived stress Subjective ratings of perceived stress were obtained using the VAS for anxiety (adjusted to ‘stress’ instead of anxiety; Houtman & Bakker, 1989) at the end of the RL and VR training (after
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