John Taverniers

High-intensity stress elicits robust cortisol increases, and impairs working memory and visuo-spatial declarative memory in Special Forces candidates: A field experiment.

While running a selection procedure, 27 male Belgian Special Forces candidates, with a mean age of 27.4 years (SD = 5.1), were randomly assigned to a no-stress control (n = 14) or a high-intensity stress group (n = 13). Participants in the latter group were exposed to an extremely strenuous mock prisoner of war (POW) exercise. Immediately after stress or control treatment, working memory and visuo-spatial declarative memory performances were measured by the digit span (DS) test and the Rey–Osterrieth complex figure (ROCF), respectively. Concurrently, stress levels were assessed by obtaining salivary cortisol measurements and subjectively by the NASA Task Load Index (TLX). As expected, exposure to high-intensity stress led to both robust cortisol increases and significant differences in TLX scores. Stress induction also significantly impaired DS and ROCF performances. Moreover, delta cortisol increases and ROCF performance in the POW stress group showed a significant negative correlation, while DS performances followed the same tendency. Summarizing, the current findings complement and extend previous work on hormonal stress effects, and the subsequent performance deterioration on two memory tests in a unique high-intensity stress environment.

Delayed memory effects after intense stress in Special Forces candidates: Exploring path processes between cortisol secretion and memory recall

The aim of this paper is twofold. First, it explores delayed effects of high endogenously evoked cortisol concentrations on visuo-spatial declarative memory. Subsequently, it applies multiple mediation (MM) analyses to reveal path processes between stress and cognitive performance in a sample of 24 male Special Forces (SF) candidates (mean age = 27.0 years, SD = 4.1). The SF candidates were randomly assigned to a control (n = 12) or an intense stress group (n = 12), and cortisol secretion for the intense stress condition was triggered by a brusque 60 min prisoner of war exercise. Stress exposure provoked robust increases in cortisol concentrations and a significant decline in immediate recall performance, measured with the Rey–Osterrieth Complex Figure (ROCF). The relative retrieval differences in regard to the ROCF persisted even after a recovery period of 24 h, as both groups showed similar levels of memory decline over 24 h. Next, the study applied a MM design that involved distribution-independent asymptotic and resampling strategies to extend traditional bivariate analyses. MM results showed that ROCF performance was mediated by increases in cortisol concentrations. Considering the studied variables, the current analysis was the first to provide statistical support for the generally accepted thesis that cortisol secretion in itself, rather than subjective strain or the experimental treatment, affects cognitive performance. The revelation of such path processes is important because it establishes process identification and may refine existing paradigms.

Force-on-Force Handgun Practice An Intra-Individual Exploration of Stress Effects, Biomarker Regulation, and Behavioral Changes

Objective: The aim of this study was to explore human factors aspects of reality-based “force-on-force” (FoF) handgun practice through a within-subjects field experiment that assessed subjective stress measurements, biomarker regulation, performance outcomes, and behavioral adaptations. Background: FoF handgun practice is a recent training asset for armed officers whereby dynamic opponents may act, react, and even retaliate with specially designed marker ammunition. Predesigned scenarios enable trainees to practice in a simulated real-life environment. Method: A sample of experienced military personnel (N = 20) ran a handgun workshop in two conditions: FoF practice and traditional cardboard-target practice. Intra-individual assessments included anticipated distress, subjective stress, salivary alpha-amylase (sAA), shooting accuracy, and directly observable training seriousness. Results: Compared with the standard cardboard practice condition, FoF exposure caused significant increases in anticipatory distress, subjective stress, and sAA secretion. Furthermore, participants’ first encounter with FoF practice (vs. cardboard practice) substantially degraded their shooting performance and had a significant positive impact on the earnestness with which they approached their mission during the workshop. Conclusion: FoF practice is an effective training tool for armed officers because it simulates a realistic work environment by increasing task-specific stress such that it affects important outcomes of professional performance and leads to desirable behavioral changes during training. Application: Potential applications of this research include the introduction of biomarker assessments in human factors research and the design, based on reality-based practice, of effective training procedures for high-reliability professionals.

Hardiness Promotes Work Engagement, Prevents Burnout, and Moderates Their Relationship

We examined the relationships between hardiness, work engagement, and burnout. Participants were Belgian service members involved in the International Security and Assistance Force (ISAF) operation. They completed a questionnaire containing hardiness items from the revised Norwegian Hardiness Scale, items concerning vigor and dedication from the Utrecht Work Engagement Scale, and those tapping cynicism and emotional exhaustion from the Utrecht Burnout Scale. Results showed that hardiness was positively related to dedication and vigor, and negatively to cynicism and emotional exhaustion. Our results further suggest that work engagement and burnout are the opposite ends of a continuum. However, analyses concerning the moderation effect of hardiness suggest that individual differences could imply different processes in the relationship between work engagement and burnout.

Hardiness differentiates military trainees on behavioural persistence and physical performance

Hardiness is a personality trait that drafts courage and motivation during adversity. Research showed that hardiness differentiates elite athletes from their lower rank competitors. In the domain of sport psychology, hardiness also strongly predicts physical performance. Because the military occupation requires resilience and excellence in physical performance, researchers investigated hardiness and behavioural persistence during training. However, in those studies, hardiness’ impact was weak. Besides, military researchers seldom addressed hardiness’ effect on physical performance. We investigated the influence of hardiness on behavioural persistence and physical performance during the military basic training. Participants were 233 trainees involved in a 22-week long basic training. They completed hardiness measures at the beginning of the training and then, two months later, we registered who stayed involved and who had dropped out. The remaining trainees participated in a self-defence exercise and their trainers evaluated their performance. Our analysis indicated that hardiness significantly predicted behavioural persistence: the trainees still involved in the training after two months scored significantly higher on the hardiness scale than those who dropped out (EXP(B) = 1.08; p < .05). Our results however confirm that hardiness has a weak direct effect on persistence of military trainees. During the self-defence exercise, hardiness positively predicted physical performance ( = 9.87; p < .05). We discuss the possible relation of hardiness with other major persistence predictors in the military, such as health, health practices, and social support. Our study is the first to indicate a strong relationship between hardiness and soldiers’ physical performance.

Soldier Health Habits and the Metabolically Optimized Brain

Human performance enhancement was the subject of a NATO workshop that considered the direct benefits of individual soldier health and fitness habits to brain health and performance. Some of the important health and fitness include physical activity and purposeful exercise, nutritional intake, sleep and rest behaviors, psychological outlook and mindfulness, and other physiologically based systemic challenges such as thermal exposure. These influences were considered in an integrated framework with insights contributed by each of five participating NATO member countries using representative research to highlight relevant interrelationships. Key conclusions are that (1) understanding the neurobiological bases and consequences of personal health behaviors is a priority for soldier performance research, and this also involves long-term brain health consequences to veterans and (2) health and fitness habits have been underappreciated as reliably effective performance enhancers and these should be preferred targets in the development of scientifically based recommendations for soldier brain health and performance.