1. Exercise and Stress Reactivity
in Animals and Humans:
A Meta-Analysis
Ernesto Ramirez

2. The majority of American experience high
levels of stress.
50% believe their level of stress has increased
over the last five years

3. Stress & Health
↑ Stress leads to hypertension
↑ Stress leads to atherosclerosis, CHD
↑ Reactivity = heart attack
• Animal studies support these findings

4. Stress & Immunity
↑ Stress = longer wound healing
↑ Stress = activation of latent viruses
↑ Stress = dysfunctional response to
bacterial challenger
↑ Stress = ↑ sick days (children)

5. Physiology of Stress
Stress produces a variety of nuerochemical
changes involving various endocrine and
catecholamine responses which facilitate
changes at specific target tissues.

6. STRESSOR
Cortex
Thalamus
Hypothalamus
Anterior Hypothalamus Posterior Hypothalamus
CRH
Amygdala
TRF
5‐HT DA Pituitary
ACTH
GABA TTH
Adrenal Cortex
Thyroid Gland
Adrenal Medulla
NE E GCs VAP OXY THY
Target Tissue
Response

7. Cross Stressor Hypothesis
Sothman proposed that exercise acts as a stressor.
• Creates a positive adaptation
• Generalized pattern carriers over to psychological
stress

8. Exercise & Stress:
Previous Reviews
Two qualitative reviews and three quantitative reviews
do not provide a clear consensus.
• Mixed results
• Inclusion of methodologically weak studies

9. Develop an understanding of the effect of exercise
on stress reactivity using meta-analytical
techniques.
• Only randomized controlled trials
• Examine both human and animal literature
• Animal research uses stringent protocols
• Allows for a glimpse into mechanisms not
able to be studied in humans

10. Methods
Literature Search
• Utilized electronic databases (PsychInfo, PubMed,
Sport Discus, Dissertation & Thesis, etc.)
• Key Words: Exercise, Randomized Controlled Trial,
Stress, Cardiovascular, Training, Physical Activity,
Recovery, Reactivity
• For animal studies: Rat, Wheel Running, Stress,
Reactivity, Recovery, Training
• Cross referenced all studies as well as previously
published meta-analyses and reviews.

11. Methods
Inclusion Criteria
Human (Meta I)
• Random assignment to groups
• Include no-treatment control group
• Cannot use physiological stressors (i.e. exercise)
Animal (Meta II)
• Random assignment to groups
• Include no-treatment control group
• Cannot use physiological stressors (i.e. exercise)
• Physical Activity/Exercise cannot be forced. Animals
allowed free wheel running.

12. Effect Size
ES Calculation
• Hedges g:
• µexp – µcontrol / SDpooled
• Corrected ES’s based upon sample size
• Overall weighted effect size
• Weighted by inverse of variance
• Homogeneity of variance
• All moderators were examined regardless of
homogeneity

13. Results
Meta I
• 150 studies located; 47 met criteria
• 30 used in analysis (lack of data)
• Resulted in 33 studies (multiple studies per article)
• N = 1,252, avg. N = 39.13
• 196 effect sizes
• Overall weighted effect size = -.31
• (95% CI = -.43,-.20)

14. Results
Meta II
• 50 studies located; 34 met criteria
• 19 articles had sufficient data
• 27 studies included (5 studies has multiple groups)
• N = 462, avg N = 17.11
• Overall weighted ES = -.33
• (95% CI = -.15, -.52)

15. Discussion
1. Exercise is beneficial for the reduction of stress
reactivity in humans.
2. Moderate effect is representative of Grade A, Level
1 evidence.
3. Much more research is needed in this area;
1. Additional RCTs (only 22% of located studies).
2. Different populations – unhealthy may need it most.
3. Incorporation of alternative treatments and stressors
4. Large sample size.
5. Investigation of immune system response

16. Discussion
1. Chronic free-wheel running leads to moderate
reductions in stress reactivity for animals.
2. Based primarily on neuroendocrine markers of
stress system response.
3. Future research must be more focused:
1. Training methods to create fitness changes.
2. Clear and repeatable stress protocols.
3. Inclusion of “human like” psychological stressor.
4. Investigation of immune system response

17. Conclusion
This is the first study to look at both animal and
human research.
• Consistent findings indicate that exercise programs have
posiJve, observable, and replicable effects on the
response to stress.
• Provides support for the use of animals to inves=gate
poten=al mechanisms that link exercise and mental well‐
being.
• An understanding of neural changes which are unavailable
in human research will lead to stronger recommenda=ons
in the future.

18. Thank You