Practical Psychophysiological Monitoring Through Wearable Technology: Single Subject Case Study

Practical Psychophysiological Monitoring Through Wearable Technology: Single Subject Case Study

Background:
Operational training manoeuvres pose multiple stressors upon military personnel, including impaired nutritional status, sleep deprivation, and near continuous load carriage. Such military specific stressors are an important performance consideration for military personnel (Parnell et al., 2018). Objective monitoring of physiological fatigue in military personnel is paramount to performance, yet is difficult to integrate without hinderance to military operations. For example, military personnel are often equipped with consistent load carriage of approximately 30kg of load carriage (Bustos et al.,, 2021) including tactical equipment required to perform their duties. Traditional physiological fatigue monitoring protocols, such as neuromuscular force production measured via force plates, requires additional load requirements to transport in the field, potentially increasing load carriage of military personnel. Therefore, the addition of fatigue monitoring equipment should be focused on lightweight wearable technology that does not impact on physical movements or impair the operational capacity of military personnel.
Psychophysiological Integration:
Lightweight wearable technology allows for non-invasive assessment and measure of psychophysiological metrics in real-time. Heart rate monitoring has previously been integrated within military research and operations providing a measure of physical load and fatigue (Bustos et al., 2021), however aspects of cognitive load and mental fatigue is yet to be effectively integrated. The recent immergence of non-invasive pupillometry and eye-tracking devices, offers a novel approach to psychophysiological fatigue monitoring. Within pupil behaviour, the task evoked pupil response (TEPR) involves the pupil diameter increasing (dilation) with arousal during tasks and returning to baseline with task completion or removal of stimulus (Beatty & Kahneman, 1966). Although an increased arousal is beneficial in military operations, hyper-arousal or frequent prolonged states of arousal can impact cognitive effort, displaying a reduced dilation capacity in TEPR (Cabestrero et al., 2009). The real-time adjustment in pupil size provides an accurate reflection of cognitive load during operational tasks enabling an objective quantification of the cognitive load imposed on military personnel. The inclusion of protective eye-tracking glasses such as Pupil Labs Neon (Pupil Labs, Berlin, Germany) to recording pupil behaviour and gaze tracking, and advanced smart garments such as Hexoskin (Carre Technologies Inc., Montreal, Canada) to measure and record physiological metrics of cardiorespiratory function, via electrode sensors embedded within textiles, provides an integrated analysis of psychophysiological variables in real-time with little impact to military personnel. The real-time monitoring of these metrics can allow accurate recovery prescription and adjustment to training load for optimal physical and mental performance of military personnel, enhancing the operational capabilities within Defence.
Implications for Defence:
The integration of lightweight, non-invasive wearable technology, such as Hexoskin and Pupil Labs Neon, offers potential to monitor psychophysiological metrics in real-time without adding significant weight or hinderance to military personnel. This dual monitoring considers individual fatigue and arousal levels during military specific activity, providing opportunity to tailor training regimens based on individual responses, potentially enhancing training outcomes by preventing overtraining, injury, and physical or cognitive exhaustion.