Max Schadt 12/07/09

Introduction  Psychosocial: the interaction between psychological and social factors (TSST for example)  Does physical activity (chronic or acute) modulate physiological responses to psychosocial stressors?  Sympathetic Nervous System and HPA-axis

Why is this important?  Hypertension, chronic stress, and hyper-reactive stress responses can lead to the development of a multitude of cardiovascular diseases.  If physical exercise has assuaging effects on BP, HPA-axis response, or SNS response, it would be greatly beneficial in the prevention and treatment of cardiovascular diseases.

Blood Pressure  Meta-analysis of 15 studies, 10 out of 15 demonstrated a significant decrease in blood pressure response to a psychosocial stressor after acute aerobic exercise  Systolic BP -3.7 mmHg (millimeter of mercury) ± S.D.  Diastolic BP -3.0 mmHg ± S.D.  Minimum effective aerobic exercise dose 30 min at 50% Vo 2 max  Larger exercise bouts mediates greater effects

Primary Study  Study examined the effects of fitness levels on HPA-axis and SNS stress reactions  Cortisol levels and heart rate were measured before, during, and after the TSST  Three subject groups based on fitness levels: elite sportsmen, amateur sportsmen, and untrained men

HPA-axis  Baseline cortisol levels and subsequent measurements  Statistically significant differences between elite group and both other groups

Heart Rate (cardiovascular response)  Heart rate measurement starting one minute prior to TSST  Considerable difference between sportsmen and untrained men  With S.E.M. sportsmen groups are not significantly different

Results  Elite sportsmen showed lower HPA-axis and SNS reactions than untrained men  Results suggest physical fitness levels correlate with stress reactions  Also, SNS may be more sensitive to the effects of physical exercise than the HPA-axis because amateur sportsmen only showed reduced response in the SNS

Alternate Study  Similarly designed study was completed by five of the same researchers two years earlier  Results were similar  In latest study, the researchers specifically stated that baseline cortisol and heart rate levels were taken before participants were told the details of the stress test  This statement is not included in previous study, suggesting that the same procedure was not followed

Cortisol Comparison  Baseline cortisol levels significantly differ between trained men groups (p = 0.004) and untrained men group (p = 0.028)

Heart Rate Comparison  Baseline heart rate for the trained sportsmen group with no knowledge of TSST was significantly lower than the trained group that presumably knew of the stressor before basal testing (p = 0.02)

Conclusion  High levels of physical training may correlate with decreased heart rate reactivity when facing an unknown psychosocial stressor  High training was associated with lower cortisol and heart rate responses than healthy, untrained controls  Intermediate fitness was correlated with reduced heart rate compared to controls, but similar cortisol levels