Objective: This study aimed to evaluate runners in a mountain ultra-marathon in terms of changes in their urine components and characteristics, in order to facilitate the creation of guidelines for running such races safely.
Design: This was a prospective observational study of 24 participants in the Trans Japan Alps Race 2014, a 415-km mountain ultra-marathon.
Methods: Urine samples were collected from participants 5 times: before the race, at 3 checkpoints (CP) mid-race (CP1: elevation of 2,870 m, 192.8 km from the start; CP2: 1,424 m, 236.8 km; CP3: 2,610 m, 290.7 km), and at the finish line. Urinalysis was performed immediately after collection to qualitatively measure 10 urine components.
Results: Urine samples of participants who completed the race tested positive for urobilinogen at a higher rate than before the race (0%), at CP2 (66.7%; p=0.008), CP3 (42.9%; p=0.031), and at the finish line (61.5%; p=0.008). Samples collected at CP3 tested positive for ketone bodies at a higher rate than before the race (50% vs. 0%, p=0.016). Significant correlations between protein and specific gravity were observed at each measurement point (before the start, rs=0.733, n=14, p=0.003; CP2, rs=0.627, n=12, p=0.029, CP3, rs=0.778, n=14, p=0.001, finish, rs=0.754, n=13, p=0.046).
Conclusions: Our findings suggest that runners in ultra-marathons experience hemolysis as a result of mechanical and physical stress, and have increased fatty acid metabolism. Impaired renal function may be detected by screening for urinary protein and specific gravity.
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