Serum creatine kinase elevations in ultramarathon runners at high altitude

Phys Sportsmed. 2017 May;45(2):129-133. doi: 10.1080/00913847.2017.1280371. Epub 2017 Jan 24.


Objectives: Creatine kinase (CK) is a sensitive enzyme marker for muscle damage in athletes. Elevated CK levels have been reported in many endurance physical activities. The consequence and possible long-term sequela of the CK elevation in athletes is unknown. There is a paucity of literature stating actual numerical values of CK associated with competing in an ultramarathon with extreme environmental conditions. Our hypothesis was that the serum CK levels increase significantly as a result of running a 161 km ultramarathon at high altitude.

Methods: This was a prospective observational study of participants of the Leadville 100 ultramarathon race in Leadville, Colorado at high altitude (2800-3840 m) in August 2014. We collected blood samples from sixty-four volunteer runners before and eighty-three runners immediately after the race.

Results: Out of 669 athletes who started the race, 352 successfully completed the race in less than the 30-hour cut-off time (52%). The majority of runners were male (84%). We were able to collect both pre- and post-race blood samples from 36 runners. Out of these 36 runners, the mean pre-race CK was increased from 126 ± 64 U/L to 14,569 ± 14,729 U/L (p < 0.001). There was a weak linear correlation between lower sodium levels and higher CK levels post-race (p = 0.003; R2 = 0.10). Using a multiple regression model, other than a negative correlation between sodium and CK levels (p = 0.001), there were no statistically significant correlations between post-race CK levels and athletes' age, BMI, or finishing time.

Conclusions: Significant elevation of CK level occurs as a result of running ultramarathons. The majority of athletes with significantly elevated CK levels were asymptomatic and required no major medical attention.

Keywords: Ultra-endurance; rhabdomyolysis; running.

MeSH terms

  • Adult
  • Aged
  • Altitude*
  • Athletes
  • Biomarkers / blood
  • Colorado
  • Competitive Behavior
  • Creatine Kinase / blood*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Physical Endurance / physiology*
  • Prospective Studies
  • Running / physiology*
  • Sodium / blood


  • Biomarkers
  • Sodium
  • Creatine Kinase