title: Serum creatine kinase elevations in ultramarathon runners at high altitude.
abstract: 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.
  
  
  
  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.
  
  
  
  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.
  
  
  
  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.
authors.affiliation: a Division of Orthopedics , Children's Hospital of Philadelphia , Philadelphia , PA , USA.
authors.forename: Danielle
authors.initials: D
authors.lastname: Magrini
authors.affiliation: b Department of Family Medicine, Division of Sports Medicine , University of Colorado School of Medicine , Denver , CO , USA.
authors.forename: Morteza
authors.initials: M
authors.lastname: Khodaee
authors.affiliation: c Department of Physical Medicine and Rehabilitation, Division of Sports Medicine , University of Colorado School of Medicine , Aurora , CO , USA.
authors.forename: Iñigo
authors.initials: I
authors.lastname: San-Millán
authors.affiliation: d Exercise Science Program, Oakland University School of Health Sciences , Rochester , MI , USA.
authors.forename: Tamara
authors.initials: T
authors.lastname: Hew-Butler
authors.affiliation: e Department of Orthopedics, Division of Sports Medicine , University of Colorado School of Medicine , Aurora , CO , USA.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Provance
mesh_terms: D000328:Adult; D000368:Aged; D000531:Altitude; D056352:Athletes; D015415:Biomarkers / Q000097:blood; D003120:Colorado; D003163:Competitive Behavior; D003402:Creatine Kinase / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance / Q000502:physiology*; D011446:Prospective Studies; D012420:Running / Q000502:physiology*; D012964:Sodium / Q000097:blood
chemical_list: D015415:Biomarkers; D012964:Sodium; D003402:Creatine Kinase
keywords: Ultra-endurance; rhabdomyolysis; running