Improvements in gait speed and weight shift of persons with traumatic brain injury and vestibular dysfunction using a virtual reality computer-assisted rehabilitation environment.

Many people sustaining a traumatic brain injury experience vestibular pathology requiring physical therapy for treatment. This study measured improvements in gait speed and weight shift for subjects receiving vestibular physical therapy using a Computer-Assisted Rehabilitation Environment (CAREN). A 6-session CAREN, 6-session traditional vestibular therapy group was compared with a 12-session CAREN only (0 traditional sessions) therapy group. These two groups were compared to each other and with data from healthy controls performing similar tasks on the CAREN. Those participating in 12 CAREN sessions had greater improvements in gait speed (p=0.014) and weight shift scores (p<0.001) and demonstrated similar values achieved by a healthy control population.

Effects of dehydroepiandrosterone supplementation during stressful military training: a randomized, controlled, double-blind field study.

Dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS) are anabolic prehormones involved in the synthesis of testosterone. Both have been shown to exert neuroprotective effects during stress. In this randomized, controlled, double-blind field study, we examined the effects of a 12-day DHEA regimen on stress indices in military men undergoing survival training. Forty-eight men were randomized to either a DHEA treatment group or placebo control group. The treatment group received 50 mg of oral DHEA supplementation daily for 5 days during classroom training followed by 7 days of 75 mg during stressful field operations. Control subjects received identical placebo pills. Salivary assays (DHEA[S], testosterone, and cortisol) were conducted at four time points: distal pre-stress (T1), proximal pre-stress (T2), mock-captivity stress (T3), and 24 h recovery (T4). Subjective distress was also assessed at T1, T3, and T4. As expected, DHEA treatment resulted in higher salivary concentrations of DHEA and DHEAS during daily living, mock-captivity stress, and recovery. Similar patterns were observed for salivary markers of anabolic balance: DHEA/cortisol, DHEAS/cortisol, and testosterone/cortisol concentration ratios. Despite notable time effects, no group differences emerged for subjective distress. A brief, low dose DHEA regimen yielded large increases in salivary DHEA(S) concentrations and enhanced anabolic balance throughout sustained military stress. These physiological changes did not extrapolate to subjective distress.

Effect of psychological skills training during military survival school: a randomized, controlled field study.

In this randomized, controlled field study, we examined the effects of a brief psychological skills training (PST) intervention on stress responses during military survival school. A second purpose was to build upon prior research in this unique environment by extending the follow-up window to 3 months. Baseline subjective distress (dissociative) symptoms were measured in 65 male military subjects, who were then randomized either to PST or a control group that received no training beyond the normal survival school curriculum. PST received training in arousal control, mental imagery, goal setting, and positive self-talk in two separate 40-minute sessions before stressful field exercises. Stress symptoms were then assessed during a mock-captivity phase of training, as well as 24 hours, 1 month, and 3 months after completion of training. Repeated-measures analyses of variance with follow-up paired t tests examined differences between groups and across time. Survival training precipitated remarkable increases in subjective distress, but few substantive group differences emerged. This study extends prior work quantifying the human stress response to intense military training.

Anger expression and stress responses in military men.

INTRODUCTION: A better understanding of individual differences in the human stress response may enhance prevention and treatment of operational stress reactions. In this study, we examined the relationships of anger experience and expression to stress indices during daily living and in response to military survival training in 45 men. METHODS: Prior to participation in survival training, subjects completed self-report measures of perceived stress and anger. The revised Impact of Event Scale was then administered 24 h after the conclusion of training. RESULTS: As expected, outward anger expression was positively associated with perceived stress during free living (P < 0.0125). Outward anger expression, inward anger expression, and angry temperament then combined to account for 25% of the variance in psychological impact of a stressful mock-captivity challenge. CONCLUSION: Anger characteristics are associated with human stress endpoints, both during daily living and in response to an ecologically valid stressor. These findings may assist in the prevention and treatment of operational stress reactions.

Behavioral predictors of acute stress symptoms during intense military training.

A better understanding of factors influencing human responses to acute stress is needed to enhance prevention and treatment of stress-related disorders. In the current study, the authors examined predictors of acute stress symptoms during intense military training in 35 men. In univariate and multivariate models, perceived stress, passive coping, and emotion-focused coping during daily living predicted acute stress symptoms in response to realistic survival training, whereas active coping and problem-focused coping did not. Baseline stress levels and coping styles, both of which may be modifiable, appear to play a fundamental role in the human response to acute uncontrollable stress. Additional research is needed to better elucidate the relative and interactive contributions of behavioral predictors of acute stress.

Physical fitness influences stress reactions to extreme military training.

BACKGROUND: Physical fitness and physical conditioning have long been valued by the military for their roles in enhancing mission-specific performance and reducing risk of injury in the warfighter. It is not known whether physical fitness plays a causal role in attenuating acute military stress reactions or the evolution of post-traumatic stress disorder. OBJECTIVE: The objective of this study was to determine whether physical fitness influences the impact of stressful events during military survival training in 31 men. METHODS: Participants self-reported their most recent Physical Readiness Test scores and completed a trait anxiety measure before survival training. Participants also completed the Impact of Events Scale (IES) 24 hours after training. RESULTS: Aerobic fitness was inversely associated with the total IES score (p < 0.01, adjusted R2 = 0.19). When adjusted for trait anxiety, this relationship was substantially attenuated and no longer significant (p = 0.11). Trait anxiety was inversely associated with aerobic fitness (p < 0.05) and positively related to IES (p < 0.001). CONCLUSIONS: Physical fitness may buffer stress symptoms secondary to extreme military stress and its effects may be mediated via fitness-related attenuations in trait anxiety.

Trait anxiety and salivary cortisol during free living and military stress.

INTRODUCTION: Accumulating evidence suggests that negative affect is associated with elevated cortisol. Limited research has investigated this association in young, highly functioning, and stress-resilient populations. METHODS: We examined the relation of trait anxiety with total and diurnal salivary cortisol during free-living conditions and during a stressful military exercise in 26 military men ages 19-30 yr (M = 21.6, SD = 2.3). Salivary cortisol was assessed at five time points over 2 consecutive days of free-living measurement, and three time points during a stressful military experience. Trait anxiety was measured with the trait portion of the Spielberger State-Trait Anxiety Inventory 1-3 wk prior to the military exercise. RESULTS: Total cortisol concentrations were similar between men reporting high or low anxiety during free-living conditions (8.6 +/- 3.2 vs. 7.4 +/- 2.8 nmol x L(-1), respectively, P > 0.05), and military stress (21.3 +/- 7.3 vs. 19.0 +/- 7.0 nmol x L(-1), respectively, P > 0.05). The diurnal cortisol profile differed significantly (P = 0.04) between these men during the free-living condition, but not the stressful military experience (P > 0.05). Specifically, during free living, men with low anxiety exhibited a diurnal cortisol pattern that peaked in the early morning, decreased precipitously during the midmorning, and continued to decrease throughout the day, reaching a nadir in the evening. By contrast, the cortisol pattern of high-anxiety men remained elevated and significantly higher than their low-anxiety counterparts during the midmorning, decreased more slowly throughout the day, and reached its lowest level in the evening. Results were not substantially altered following adjustment for sleep duration or wake time. CONCLUSION: These findings suggest that trait anxiety influences the diurnal cortisol pattern in young, apparently healthy men during free-living conditions, but does not predict the cortisol response to uncontrollable military stress.

Stressful military training: endocrine reactivity, performance, and psychological impact.

INTRODUCTION: We examined the responsiveness of both cortisol and dehydroepiandrosterone sulfate (DHEAS) to the stress of survival training in military men and evaluated relationships to performance, peritraumatic dissociation, and the subsequent impact of stressful events. METHODS: Baseline salivary cortisol samples were self-collected by 19 men at 0900 and 1930 in a free-living (FL) environment. DHEAS samples were also collected in a subset of this sample (N = 12). Samples were subsequently taken at similar time points during a stressful captivity (SC) phase of training. Repeated-measures analyses of variance with follow-up paired t-tests examined differences across time and conditions. RESULTS: Significant increases were observed at both time points (0900 and 1930) from FL to SC in both cortisol (0900: 9.2 +/- 3.4 nmol x L(-1) vs. 18.4 +/- 10.5 nmol x L(-1); 1930: 3.5 +/- 3.0 nmol x L(-1) vs. 27.7 +/- 10.9 nmol x L(-1)) and DHEAS (0900: 1.7 +/- 1.3 ng x ml(-1) vs.6.7 +/- 3.5 ngx ml(-1); 1930: 1.5 0.84 ng x ml(-1) vs. 4.5 +/- 3.0 ng x ml(-1)). Also, overall performance during a high-intensity captivity-related challenge was inversely related to the DHEAS-cortisol ratio; conversely, overall performance during a low-intensity captivity-related challenge was positively related to DHEAS at the 0900 time point during SC. Dissociation was unrelated to endocrine indices measured during SC, while total impact of events was inversely related to percent change in DHEAS from FL to SC. CONCLUSIONS: Cortisol and DHEAS increase in response to allostatic load, and may relate to human performance during SC as well as PTSD symptoms.