Clinical Impact of Speed Variability to Identify Ultramarathon Runners at Risk for Acute Kidney Injury

RESEARCH ARTICLE Clinical Impact of Speed Variability to Identify Ultramarathon Runners at Risk for Acute Kidney Injury Sen-Kuang Hou1,2,3, Yu-Hui Chiu2,4, Yi-Fang Tsai5,6, Ling-Chen Tai5, Peter C. Hou3,7, Chorng-Kuang How6,8, Chen-Chang Yang2, Wei-Fong Kao1,2* a11111 1 Department of Emergency Medicine, Taipei Medical University Hospital, Taipei, Taiwan, 2 Institute of Environmental and Occupational Health Sciences, National Yang-Ming University, Taipei, Taiwan, 3 Department of Emergency Medicine, Brigham and Women’s Hospital, Boston, Massachusetts, United States of America, 4 Department of Emergency Medicine, Mackay Memorial Hospital, Taipei, Taiwan, 5 Department of General Surgery, Taipei Veterans General Hospital, Taipei, Taiwan, 6 Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan, 7 Harvard Medical School, Boston, Massachusetts, United States of America, 8 Department of Emergency Medicine, Taipei Veterans General Hospital, Taipei, Taiwan * Abstract OPEN ACCESS Background Citation: Hou S-K, Chiu Y-H, Tsai Y-F, Tai L-C, Hou PC, How C-K, et al. (2015) Clinical Impact of Speed Variability to Identify Ultramarathon Runners at Risk for Acute Kidney Injury. PLoS ONE 10(7): e0133146. doi:10.1371/journal.pone.0133146 Ultramarathon is a high endurance exercise associated with a wide range of exerciserelated problems, such as acute kidney injury (AKI). Early recognition of individuals at risk of AKI during ultramarathon event is critical for implementing preventative strategies. Editor: Dirce Maria Trevisan Zanetta, School of Public Health of University of São Paulo, BRAZIL Objectives Received: April 1, 2015 To investigate the impact of speed variability to identify the exercise-related acute kidney injury anticipatively in ultramarathon event. Accepted: June 23, 2015 Published: July 15, 2015 Methods Copyright: © 2015 Hou et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 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 postrace, 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. Data Availability Statement: All relevant data are within the paper. Funding: This study was supported by a grant from Taipei Veterans General Hospital, Taiwan (Grant V100C-202). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. 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 PLOS ONE | DOI:10.1371/journal.pone.0133146 July 15, 2015 1 / 11 Speed Variability to Identify AKI in Ultramarathon 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. Introduction Ultramarathon, a foot race longer than the standard 42.2 kilometer (km) marathon distance, has become increasingly popular in recent decades throughout the world [1]. During this endurance event, athletes provoke many physiological responses and metabolic adaptations to finish the competition [2]. However, higher level of the physiological demands may induce a wide range of exercise-related injuries, such as electrolyte imbalance [3,4], exertional heat stroke [5,6], rhabdomyolysis, acute kidney injury [7–9], and even cardiac arrest [10,11]. With the growing numbers of participants, early recognition of runners at risk for the development of exercise-related injuries is paramount. In the literature, several studies reported that 40–80% of athletes developed acute kidney injury (AKI) after strenuous exercise [12–14]. The pathophysiology of exercise-related AKI is multi-factorial [15] and may be the combined effect of dehydration, hot environment [16,17], nonsteroid anti-inflammatory drugs use [18,19], hyperuricemia [9,15], and rhabdomyolysis [7–9]. During ultramarathon, early recognition and management of runners at risk of impending kidney injury/failure are critical to prevent serious complications. Although the diagnosis of AKI can be made by checking the serum creatinine level before and after the race, it may not be feasible to identify individuals at risk of the development of AKI early during the ultramarathon event. Although the running speed of ultramarathon might be influenced by several factors such as altitude changes, temperature, humidity, and fatigue, runners strategize to maintain appropriate speed in response to physical condition to avoid falling into over-fatigued [20–22]. Some studies reported that the variability of speed may affect the performance and metabolic demand in different-distance running [23–26]; however, there is no published data evaluating the relationship between variability of speed and exercise-related injuries, such as AKI, during ultramarathon running. The aim of the study is to investigate the association of speed variability to identify exercise-related acute kidney injury during an ultramarathon event. PLOS ONE | DOI:10.1371/journal.pone.0133146 July 15, 2015 2 / 11 Speed Variability to Identify AKI in Ultr (...truncated)