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Related Experiment Videos

Short-term resource allocation during extensive athletic competition.

Daniel P Longman1, Sean P Prall2, Eric C Shattuck2

  • 1Department of Archaeology and Anthropology, University of Cambridge, Cambridge, United Kingdom.

American Journal of Human Biology : the Official Journal of the Human Biology Council
|October 11, 2017
PubMed
Summary

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This summary is machine-generated.

Ultramarathon runners showed decreased testosterone and libido after racing. This shift in energy priorities favors immune defense over reproduction during extreme physical stress.

Area of Science:

  • Human physiology
  • Life history theory
  • Immunology

Background:

  • Life history theory predicts trade-offs between reproduction and somatic maintenance under energetic stress.
  • Severe energetic imbalance, such as during ultramarathon running, can reveal these trade-offs.

Purpose of the Study:

  • To investigate acute trade-offs between reproductive effort and somatic maintenance in male ultramarathon runners.
  • To measure changes in testosterone, libido, and innate immune function following prolonged strenuous exercise.

Main Methods:

  • Sixty-six male ultramarathon runners provided saliva and blood samples before and after a race.
  • Assessed salivary testosterone, immune markers (hemolytic complement activity, bacterial killing ability), lean body mass, and libido via image response.

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Main Results:

  • Salivary testosterone levels and arousal scores significantly decreased post-race.
  • Bacterial killing ability and hemolytic complement activity significantly increased post-race.

Conclusions:

  • Results support life history theory predictions of an energy trade-off.
  • Heightened immune responses and decreased reproductive markers indicate a shift towards somatic maintenance during energetic stress.