Aerobic Fitness Level Affects Cardiovascular and Salivary Alpha Amylase Responses to Acute Psychosocial Stress.

BACKGROUND: Good physical fitness seems to help the individual to buffer the potential harmful impact of psychosocial stress on somatic and mental health. The aim of the present study is to investigate the role of physical fitness levels on the autonomic nervous system (ANS; i.e. heart rate and salivary alpha amylase) responses to acute psychosocial stress, while controlling for established factors influencing individual stress reactions. METHODS: The Trier Social Stress Test for Groups (TSST-G) was executed with 302 male recruits during their first week of Swiss Army basic training. Heart rate was measured continuously, and salivary alpha amylase was measured twice, before and after the stress intervention. In the same week, all volunteers participated in a physical fitness test and they responded to questionnaires on lifestyle factors and personal traits. A multiple linear regression analysis was conducted to determine ANS responses to acute psychosocial stress from physical fitness test performances, controlling for personal traits, behavioural factors, and socioeconomic data. RESULTS: Multiple linear regression revealed three variables predicting 15 % of the variance in heart rate response (area under the individual heart rate response curve during TSST-G) and four variables predicting 12 % of the variance in salivary alpha amylase response (salivary alpha amylase level immediately after the TSST-G) to acute psychosocial stress. A strong performance at the progressive endurance run (high maximal oxygen consumption) was a significant predictor of ANS response in both models: low area under the heart rate response curve during TSST-G as well as low salivary alpha amylase level after TSST-G. Further, high muscle power, non-smoking, high extraversion, and low agreeableness were predictors of a favourable ANS response in either one of the two dependent variables. CONCLUSIONS: Good physical fitness, especially good aerobic endurance capacity, is an important protective factor against health-threatening reactions to acute psychosocial stress.

Adapted marching distances and physical training decrease recruits' injuries and attrition.

There is evidence that progressive loading of physical demands at the beginning of basic military service and specific physical training can reduce injury incidences. Therefore, aim of this study was to measure the effects of a progressive increase in marching distances and an adapted physical training program on injury incidence and attrition rate in a Swiss Army infantry training school. One company reduced the distances covered on foot during the first 4 weeks of basic military training. A second company performed an adapted physical training program for 10 weeks. A third company participated in both interventions combined, and a fourth company served as a control group without any intervention. The injury incidences and attrition rates of 651 male recruits were registered during 21 weeks of military service. Several predictor variables for injury and attrition, such as physical fitness, previous injuries, level of previous physical activity, smoking, motivation, and socioeconomic factors, were assessed as well. The data were analyzed using binary logistic backward regressions. Each intervention separately had a favorable effect on injury prevention. However, combining the 2 interventions resulted in the greatest reduction in injury incidence rate (-33%). Furthermore, the adapted physical training successfully reduced the military service attrition rates (-53%).

Hair cortisol concentration is unaffected by basic military training, but related to sociodemographic and environmental factors.

The analysis of hair cortisol concentrations (HCC) is a promising new biomarker for retrospective measurement of chronic stress. The effect of basic military training (BMT) on chronic stress has not yet been reported. The aim of this study was to investigate the effect of 10-week BMT on HCC, while further exploring the role of known and novel covariates. Young healthy male recruits of the Swiss Army participated twice, 10 weeks apart, in data collection (1st examination: n = 177; 2nd examination: n = 105). On two occasions, we assessed HCC, perceived stress and different candidate variables that may affect HCC (e.g. socioeconomic status, meteorological data). Military training increased perceived stress from the first to the second examination, but did not affect HCC. In line with this, there was no correlation between HCC and perceived stress ratings. This could be interpreted as a missing influence of mainly physical stress (e.g. exercise) on HCC. In contrast, significant correlations were found between HCC and ambient temperature, humidity and education. Future studies should control for meteorological data and educational status when examining HCC.

Mood and autonomic responses to repeated exposure to the Trier Social Stress Test for Groups (TSST-G).

INTRODUCTION: A group version of the Trier Social Stress Test (TSST-G) was introduced as a standardized, economic and efficient tool to induce a psychobiological stress response simultaneously in a group of subjects. The aim of the present study was to examine the efficacy of the TSST-G to repeatedly induce an affective and autonomic stress response while comparing two alternative protocols for the second examination. METHODS AND MATERIALS: Healthy young male recruits participated twice in the TSST-G 10 weeks apart. In the first examination, the TSST-G consisted of a combination of mental arithmetic and a fake job interview (TSST-G-1st; n=294). For the second examination, mental arithmetic was combined with either (a) a defensive speech in response to a false shoplifting accusation (TSST-G-2nd-defence; n=105), or (b) a speech on a more neutral topic selected by the investigators (TSST-G-2nd-presentation; n=100). Affect ratings and salivary alpha-amylase (sAA) were determined immediately before and after the stress test, while heart rate (HR) and heart rate variability (HRV) were measured continuously. RESULTS: TSST-G-1st resulted in a significant increase of negative affect, HR, and sAA, and a significant decrease in positive affect and HRV. TSST-G-2nd, overall, resulted in a significant increase of HR and sAA (the latter only in response to TSST-G-2nd-defence) and a decrease in HRV, while no significant affect alterations were found. When comparing both, TSST-G-2nd-defence and -2nd-presentation, the former resulted in a stronger stress response with regard to HR and HRV. DISCUSSION: The findings reveal that the TSST-G is a useful protocol to repeatedly evoke an affective and autonomic stress response, while repetition leads to affective but not necessarily autonomic habituation. When interested in examining repeated psychosocial stress reactivity, a task that requires an ego-involving effort, such as a defensive speech, seems to be significantly superior to a task using an impersonal speech.