title: Clinical Impact of Speed Variability to Identify Ultramarathon Runners at Risk for Acute Kidney Injury.
abstract: BACKGROUND
  Ultramarathon is a high endurance exercise associated with a wide range of exercise-related problems, such as acute kidney injury (AKI). Early recognition of individuals at risk of AKI during ultramarathon event is critical for implementing preventative strategies.
  
  
  OBJECTIVE
  To investigate the impact of speed variability to identify the exercise-related acute kidney injury anticipatively in ultramarathon event.
  
  
  METHODS
  This is a prospective, observational study using data from a 100 km ultramarathon in Taipei, Taiwan. The distance of entire ultramarathon race was divided into 10 splits. The mean and variability of speed, which was determined by the coefficient of variation (CV) in each 10 km-split (25 laps of 400 m oval track) were calculated for enrolled runners. Baseline characteristics and biochemical data were collected completely 1 week before, immediately post-race, and one day after race. The main outcome was the development of AKI, defined as Stage II or III according to the Acute Kidney Injury Network (AKIN) criteria. Multivariate analysis was performed to determine the independent association between variables and AKI development.
  
  
  RESULTS
  26 ultramarathon runners were analyzed in the study. The overall incidence of AKI (in all Stages) was 84.6% (22 in 26 runners). Among these 22 runners, 18 runners were determined as Stage I, 4 runners (15.4%) were determined as Stage II, and none was in Stage III. The covariates of BMI (25.22 ± 2.02 vs. 22.55 ± 1.96, p = 0.02), uric acid (6.88 ± 1.47 vs. 5.62 ± 0.86, p = 0.024), and CV of speed in specific 10-km splits (from secondary 10 km-split (10th - 20th km-split) to 60th - 70th km-split) were significantly different between runners with or without AKI (Stage II) in univariate analysis and showed discrimination ability in ROC curve. In the following multivariate analysis, only CV of speed in 40th - 50th km-split continued to show a significant association to the development of AKI (Stage II) (p = 0.032).
  
  
  CONCLUSIONS
  The development of exercise-related AKI was not infrequent in the ultramarathon runners. Because not all runners can routinely receive laboratory studies after race, variability of running speed (CV of speed) may offer a timely and efficient tool to identify AKI early during the competition, and used as a surrogate screening tool, at-risk runners can be identified and enrolled into prevention trials, such as adequate fluid management and avoidance of further NSAID use.
authors.affiliation: Department of Emergency Medicine, Taipei Medical University Hospital, Taipei, Taiwan; Institute of Environmental and Occupational Health Sciences, National Yang-Ming University, Taipei, Taiwan; Department of Emergency Medicine, Brigham and Women's Hospital, Boston, Massachusetts, United States of America.
authors.forename: Sen-Kuang
authors.initials: SK
authors.lastname: Hou
authors.affiliation: Institute of Environmental and Occupational Health Sciences, National Yang-Ming University, Taipei, Taiwan; Department of Emergency Medicine, Mackay Memorial Hospital, Taipei, Taiwan.
authors.forename: Yu-Hui
authors.initials: YH
authors.lastname: Chiu
authors.affiliation: Department of General Surgery, Taipei Veterans General Hospital, Taipei, Taiwan; Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Yi-Fang
authors.initials: YF
authors.lastname: Tsai
authors.affiliation: Department of General Surgery, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Ling-Chen
authors.initials: LC
authors.lastname: Tai
authors.affiliation: Department of Emergency Medicine, Brigham and Women's Hospital, Boston, Massachusetts, United States of America; Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Hou
authors.affiliation: Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan; Department of Emergency Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Chorng-Kuang
authors.initials: CK
authors.lastname: How
authors.affiliation: Institute of Environmental and Occupational Health Sciences, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Chen-Chang
authors.initials: CC
authors.lastname: Yang
authors.affiliation: Department of Emergency Medicine, Taipei Medical University Hospital, Taipei, Taiwan; Institute of Environmental and Occupational Health Sciences, National Yang-Ming University, Department of Emergency Medicine, School of Medicine, Taipei Medical University,Taipei, Taiwan.
authors.forename: Wei-Fong
authors.initials: WF
authors.lastname: Kao
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D000328:Adult; D056352:Athletes; D001696:Biomechanical Phenomena; D015992:Body Mass Index; D003681:Dehydration / Q000150:complications / Q000503:physiopathology; D042241:Early Diagnosis; D005260:Female; D006359:Heat Exhaustion / Q000150:complications / Q000503:physiopathology; D006801:Humans; D033461:Hyperuricemia / Q000150:complications / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010807:Physical Endurance; D005082:Physical Exertion; D011446:Prospective Studies; D012372:ROC Curve; D012206:Rhabdomyolysis / Q000150:complications / Q000503:physiopathology; D012306:Risk; D012420:Running; D013624:Taiwan; D014527:Uric Acid / Q000097:blood*
chemical_list: D014527:Uric Acid