OBJECTIVE: To investigate biochemical changes related to muscle breakdown, hepatic damage, hyponatraemia, and a number of other variables in the serum of participants in a 1600 km ultramarathon run. METHODS: Blood samples were obtained from nine participants (seven men, two women) in a 1600 km foot race before, after 4 and 11 days of running, and at the conclusion of the event. Samples were analysed by standard methods and results corrected, where appropriate, for changes in plasma volume. RESULTS: Significant (p < 0.05) increases in the following variables were found during or at the conclusion of the event: plasma volume, sodium, chloride, urea, alkaline phosphatase, gamma-glutamyltransferase, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, creatine kinase, bilirubin, total protein, albumin, glucose, calcium, and phosphate. Significant (p < 0.05) decreases in the following variables were found during or at the conclusion of the event: globulin, uric acid, and cholesterol. No change occurred in serum potassium, bicarbonate, creatinine, and triglycerides. CONCLUSION: A wide range of biochemical perturbations occur during ultramarathon running but a number of variables remain within normal limits despite severe physical stress. Large increases in plasma volume occur, and hyponatraemia is rare in events of this duration. The time course of increases in enzymic indicators of muscle damage indicates that duration of running is not the sole determinant of such increases. This study provides indirect evidence of possible hepatic damage during prolonged exercise and an increase in serum calcium both of which warrant further investigation.
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