Creatine Kinase Elevations in Ultra-endurance Runners at Altitude

Abstract

Introduction: 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 these athletes is unknown. There is a paucity of literature stating actual numerical values of CK associated with competing in an ultra-endurance event with extreme environmental conditions. PURPOSE: To assess the CK levels of athletes pre- and post- the Leadville 100 race at high elevation (2800-3800m). METHODS: We collected blood samples from voluntary athletes, 65 runners (79% male) before and 84 (81% male) runners immediately after a 161-km ultramarathon in Leadville, Colorado in August 2014. CK and sodium levels were analyzed from the samples obtained. IRB approval was received prior to all data collection. RESULTS: Out of 672 athletes who started the race, 351 successfully completed the race in less than 30 hours (52%). The majority of starters and finishers were male (∼85%). We were able to collect both pre- and post-race blood samples from 37 runners. Out of 84 runners who we collected blood samples after the race, 19 were not able to successfully finish the race.Out of these 37 runners, the mean pre-race CK (PrCK) was 124±64 U/L. The mean post-race CK (PoCK ) was 14569±14729 U/L. There was a linear correlation between lower sodium levels and higher CK levels post-race (p=0.003; r2=0.10). There was no statistically significant correlations between post-race CK levels and athletes’ BMI, age, or finishing time. Based on the electronic survey conducted 1-2 weeks after the race (92% response rate), none of the athletes who we collected blood samples on visited an emergency department or a physician’s office after the race. CONCLUSION: Significant elevation of CK level occurs as a result of running ultramarathons with lower sodium levels significantly correlated with higher CK levels. The majority of athletes with significantly elevated CK levels were asymptomatic and required no major medical attention. Further studies are needed to better equip the medical team in monitoring and treating ultra-endurance athletes. This study was in part funded by the ACSM Clinical Sports Medicine Endowment Grant.