# Manipulating Stress Responses during Spaceflight Training with Virtual Stressors
## 6 Discussion  
A spaceflight emergency procedure was conducted in VR-ISS with the aim at evaluating VR stressors. The hypothesis that manipulating different levels of VR environmental stressors during an operational task can induce different levels of stress was partially supported. The results demonstrated that levels of indicators of physiological stress (HR, RMSD, EDA, SBP), subjective stress (PTSR, Free Stress Comparison), and ratings of distress, workload, and anxiety were significantly different for those training simulations. Some measures did not find significant differences, including pNN50 and DBP. Further, most measures showed differences between the low stressor and high stressors but could not discriminate the medium stressor level. Several of the physiological stress indicators were found to be different for the stressor levels. The HR was different between the low and high stressor levels and similarly different for the RMSSD. The decrease in RMSSD for the high stress indicates parasympathetic inhibition and reflects an inability to relax. Further, there was an increase in EDA which indicates sympathetic activation, which is the likely cause for the increase in HR and SBP. Altogether, this suggests the high stressor simulation was effective at inducing a robust physiological stress response. In contrast, the low and medium stressor levels were difficult to distinguish from each other and had varied physiological responses. The RMSSD remained elevated and the HR remained depressed for both levels. However, the medium level did have an increase in EDA, suggesting there was some sympathetic activation concurrent with parasympathetic attenuation. Research on cardiac autonomic balance versus cardiac regulatory capacity [65] suggests that the coactivity is still representative of a stress response, albeit a mild response due to the lack of support from other measures. The subjective stress was found to be different for the stressor levels based on immediate ratings after each trial (PTSR), ratings after the experiment (Free Stress Comparison), and changes in distress during the trials (SSSQ). The results suggest that design of the VR simulations using environmental stressors was successful at manipulating trainee stress levels. However, the distress results show that low and medium were hard to distinguish between. The cause may be attributed to which stressors were selected for the simulation, the magnitude of each environmental stressors, or the combination of different stressors (e.g., noise, smoke). Previous research has shown that different stressors can elicit varying stress responses and can have a cumulative effect that may be greater than the individual effects of the stressors alone [66; 67]. The present experiment used expert opinion to inform how the stressors training simulations but had little empirical support. By changing the stressors, magnitude, or combination, it may be possible to have the VR stressor scenarios result in physiological and distress that are more discriminable in future research. Never  
Figure 12: Anxiety obtained by the State Trait Anxiety Inventory (STAI). Error bars representing 95% confidence intervals. theless, the large effect of the stressor levels on the subjective stress measures demonstrates distinguishable training levels that can be used to induce stress in VR. The results show that the workload was higher for the high stressor compared to the other stressor levels. Because the simulations were designed to only change environment stressors and not task load, it was expected that workload would not change between the three stressor levels because the procedure was the same for each. Since workload can be thought of as a stress derived from the stressor of task load, it was predicted that the TLX rating for frustration and performance may be different, but not enough to impact the overall workload. However, it is unexpected to find a difference for the high stressor level from the TLX mental workload, physical workload, temporal, and effort.