Hormonal Responses to a 160 Km Race across Frozen Alaska

William J. Kraemer ^1*, Maren S. Fragala ¹, Greig (no middle name) Watson ¹, Jeff S Volek ¹, Kristen J. Stuempfle ², Donald R. Lehmann ³, Stephen (no middle name) Bailey ⁴, Sherri L. Hughes ⁵, Martyn R. Rubin ¹, Duncan N. French ¹, Carl M. Maresh n ¹, Jakob L. Vingren ¹, Disa L. Hatfield ¹, Barry A. Spiering ¹, Jen Yu Ho ¹, Debbie S. Evans ⁶ and H. Samuel Case ⁵

¹ University of Connecticut, United States
² Gettysburg College, United States
³ Sitka Medical Center, Sitka, AK., United States
⁴ Elon University, United States
⁵ McDaniel College, United States
⁶ Alaska Native Medical Center, Anchorage, Alaska, United States

^* To whom correspondence should be addressed. E-mail: william.kraemer{at}uconn.edu.

Accepted 12 June 2007

Abstract

Background: Severe physical and environmental stress appears to have a suppressive effect on the hypothalamic-pituitary gonadal (HPG) axis in men. Examining hormonal responses to an actual 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 (age, (Mean ± SD) 42 ± 7 y; body mass, 78.9 ± 7.1 kg; height , 1.78 ± 0.05 m) raced by bicycle (cyclists) and ten subjects (age, 35 ± 9 y; 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 hr and 33.98 ± 6.12 hr, respectively.

Results: In cyclists there were significant (p 0.05) pre- to post-race increases in cortisol (mean ± SD, 254.83 ± 135.26 to 535.99 ± 232.22 nmol•L-1), GH (0.12 ± 0.23 to 3.21 ± 3.33 µg•ml-1), and IL-6 (2.36 ± 0.42 to 10.15 ± 0.3.28 pg•ml-1), and a significant decrease in testosterone (13.81 ± 3.19 to 5.59 ± 3.74 nmol•L-1). Similarly, in runners there were significant pre- to post-race increases in cortisol (142.09 ± 50.74 to 452.21 ± 163.40 ng•ml-1), GH (0.12 ± 0.23 to 3.21 ± 3.33 µg•ml-1), IL-6 (2.42 ± 0.68 to 12.25 ± 1.78 pg•ml-1), and a significant decrease in testosterone (12.32 ± 4.47 to 6.96 ± 3.19 nmol•L-1). There were no significant differences in the hormonal concentrations between the 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.

Key Words: cortisol, growth hormone, testosterone, ultra endurance race

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