Physical Activity and Psychosocial Stress

Response

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% Vo2 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

0 20 40 60 80 1000

5

10

15

20

25

30

Salivary Cortisol Response

Elite sportsmenAmateur sportsmenUntrained men

Time (minutes)

Sa

liva

ry F

ree

Co

rtis

ol (

nm

ol/l

)

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

-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1560

70

80

90

100

110

120

Heart Rate Response

Elite sportsmenAmateur sportsmenUntrained men

Time (minutes)

He

art

Ra

te (

be

ats

/min

)

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)

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Salivary Cortisol Response

Elite sportsmenUntrained menTrained menUntrained men

Time (minutes)

Sa

liva

ry F

ree

Co

rtis

ol (

nm

ol/l

)

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)

-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1560

70

80

90

100

110

120

Heart Rate Response

Elite sportsmenUntrained menTrained menUntrained men

Time (minutes)

He

art

Ra

te (

be

ats

/min

)

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