Exercise and Stress Reactivity in Humans and Animals: A Meta Analysis

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Exercise and Stress Reactivity in Humans and Animals: A Meta Analysis

  1. 1. Exercise and Stress Reactivity in Animals and Humans: A Meta-Analysis Ernesto Ramirez
  2. 2. The majority of American experience high levels of stress. 50%
believe
their
level
of
stress
has
increased
 over
the
last
five
years

  3. 3. Stress & Health ↑ Stress leads to hypertension ↑ Stress leads to atherosclerosis, CHD ↑ Reactivity = heart attack • Animal studies support these findings
  4. 4. Stress & Immunity ↑ Stress = longer wound healing ↑ Stress = activation of latent viruses ↑ Stress = dysfunctional response to bacterial challenger ↑ Stress = ↑ sick days (children)
  5. 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. 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. 7. Cross Stressor Hypothesis Sothman proposed that exercise acts as a stressor. •  Creates a positive adaptation • Generalized pattern carriers over to psychological stress
  8. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 18. Thank You

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