A brief commentary on cardiovascular reactivity at a crossroads

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.

Resting Plasma Lipids and Cardiovascular Reactivity to Acute Psychological Stress

Abstract. Prior research suggests that hyperlipidemia is associated with elevated blood pressure responses to acute stress but whether lipid levels influence underlying cardiac and vascular determinants of blood pressure during stress is not known. Thus, we examined whether lipids were associated with stress-induced blood pressure responses and responses of stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR). In 19 healthy university students (15 men), blood was drawn to measure lipid levels (triglycerides, low-density lipoprotein cholesterol [LDL-c], high-density lipoprotein cholesterol [HDL-c], total cholesterol) after a 10-min rest period. Participants then completed a 6-min mental arithmetic stressor and a 3-min cold pressor (separated by a 10-min recovery). This procedure was repeated twice, approximately 6 weeks apart. Lipids and hemodynamic values were averaged across the two sessions. Multiple linear regression analyses revealed that a model including LDL-c, HDL-c, and triglycerides significantly predicted diastolic blood pressure (DBP), R2adj = .45, p = .007, and systolic blood pressure (SBP) cold pressor reactivity, R2adj = .35, p = .023. Individually, only LDL-c significantly predicted DBP, β = .64, p = .003, and SBP cold pressor reactivity, β = .64, p = .005. The same model marginally predicted CO, R2adj = .24, p = .069, and TPR, R2adj = 21, p = .091, reactivity to mental arithmetic, but only triglycerides were independently associated with CO, β = −.63, p = .012, and TPR, β = .54, p = .029 reactivity. Lipids were not associated with heart rate (HR) or SV reactivity. LDL-c was positively associated with the blood pressure response to the cold pressor, whereas triglycerides were positively and negatively associated with the TPR and CO responses, respectively, to mental arithmetic. Endothelial dysfunction and greater release of vasoconstrictors in those with high lipids may explain these relationships.