title: Aerobic Fitness Level Affects Cardiovascular and Salivary Alpha Amylase Responses to Acute Psychosocial Stress.
abstract: 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.
authors.affiliation: Swiss Federal Institute of Sport Magglingen (SFISM), Magglingen, Switzerland. Thomas.wyss@baspo.admin.ch.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wyss
authors.affiliation: Clinical Psychology and Psychotherapy, University of Zurich, Zurich, Switzerland.|Military Academy, Swiss Federal Institute of Technology, ETH Zurich, Zurich, Switzerland.
authors.forename: Maria
authors.initials: M
authors.lastname: Boesch
authors.affiliation: Swiss Federal Institute of Sport Magglingen (SFISM), Magglingen, Switzerland.
authors.forename: Lilian
authors.initials: L
authors.lastname: Roos
authors.affiliation: Swiss Federal Institute of Sport Magglingen (SFISM), Magglingen, Switzerland.
authors.forename: Céline
authors.initials: C
authors.lastname: Tschopp
authors.affiliation: Swiss Federal Institute of Sport Magglingen (SFISM), Magglingen, Switzerland.
authors.forename: Klaus M
authors.initials: KM
authors.lastname: Frei
authors.affiliation: Military Academy, Swiss Federal Institute of Technology, ETH Zurich, Zurich, Switzerland.
authors.forename: Hubert
authors.initials: H
authors.lastname: Annen
authors.affiliation: Clinical Psychology and Psychotherapy, University of Zurich, Zurich, Switzerland.
authors.forename: Roberto
authors.initials: R
authors.lastname: La Marca
keywords: Autonomic nervous system; Cross-stressor adaptation hypotheses; Physical activity; Physical fitness; Stress prevention; Stress response