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Hormonal responses to a 160-km race across frozen Alaska
  1. W J Kraemer1,
  2. M S Fragala1,
  3. G Watson1,
  4. J S Volek1,
  5. M R Rubin1,
  6. D N French1,
  7. C M Maresh1,
  8. J L Vingren1,
  9. D L Hatfield1,
  10. B A Spiering1,
  11. J Yu-Ho1,
  12. S L Hughes2,
  13. H S Case2,
  14. K J Stuempfle3,
  15. D R Lehmann4,
  16. S Bailey5,
  17. D S Evans6
  1. 1
    Human Performance Laboratory, University of Connecticut, Storrs, Connecticut, USA
  2. 2
    McDaniel College, Westminster, Maryland, USA
  3. 3
    Gettysburg College, Gettysburg, Philadelphia, USA
  4. 4
    Sitka Medical Center, Sitka, Arkansas, USA
  5. 5
    Elon University, Elon, North Carolina, USA
  6. 6
    Alaska Native Medical Center, Anchorage, Alaska, USA
  1. Professor W J Kraemer, PhD, University of Connecticut, Human Performance Laboratory, Storrs, Connecticut 06269-1110, USA; william.kraemer{at}


Background: Severe physical and environmental stress seems to have a suppressive effect on the hypothalamic–pituitary–gonadal (HPG) axis in men. Examining hormonal responses to an extreme 160-km competition across frozen Alaska provides a unique opportunity to study this intense stress.

Objective: To examine hormonal responses to an ultra-endurance race.

Methods: Blood samples were obtained from 16 men before and after racing and analyzed for testosterone, interleukin-6 (IL-6), growth hormone (GH) and cortisol. Six subjects (mean (SD) age 42 (7) years; body mass 78.9 (7.1) kg; height 1.78 (0.05) m raced by bicycle (cyclists) and 10 subjects (age 35 (9) years; body mass 77.9 (10.6) kg; height, 1.82 (0.05) m) raced by foot (runners). Mean (SD) finish times were 21.83 (6.27) and 33.98 (6.12) h, respectively.

Results: In cyclists there were significant (p⩽0.05) mean (SD) pre-race to post-race increases in cortisol (254.83 (135.26) to 535.99 (232.22) nmol/l), GH (0.12 (0.23) to 3.21 (3.33) µg/ml) and IL-6 (2.36 (0.42) to 10.15 (3.28) pg/ml), and a significant decrease in testosterone (13.81 (3.19) to 5.59 (3.74) nmol/l). Similarly, in runners there were significant pre-race to post-race increases in cortisol (142.09 (50.74) to 452.21 (163.40) ng/ml), GH (0.12 (0.23) to 3.21 (3.33) µg/ml) and IL-6 (2.42 (0.68) to 12.25 (1.78) pg/ml), and a significant decrease in testosterone (12.32 (4.47) to 6.96 (3.19) nmol/l). There were no significant differences in the hormonal levels between cyclists and runners (p>0.05).

Conclusions: These data suggest a suppression of the hypopituitary–gonadal axis potentially mediated by amplification of adrenal stress responses to such an ultra-endurance race in environmentally stressful conditions.

  • ultra endurance race
  • testosterone
  • growth hormone
  • cortisol

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  • Competing interests: None.

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