title: Dehydration and serum biochemical changes in marathon runners.
abstract: The effects of a competitive marathon race on serum biochemical and haematological parameters have been evaluated. Blood samples were obtained shortly before and immediately after the race; urine samples were also obtained before and after the race. Body weight was recorded pre- and post-race. During the race subjects consumed a total of 1.41 of either water or a dilute glucose-electrolyte solution. The average weight loss of the runners was 2.09 +/- 0.77 kg (mean +/- SD), corresponding to 2.9 +/- 0.8% of body weight. Small but significant increases in both haematocrit and haemoglobin concentration occurred; plasma volume was calculated to decrease by 4.7%. Serum potassium concentration showed no change, but the response was highly variable; serum sodium concentration increased in line with the decrease in plasma volume. In the group of subjects drinking water during the race, the pre-race plasma glucose concentration was 5.3 +/- 1.2 mmol . l-1, this was unchanged after the race (5.0 +/- 1.2 mmol . l-1). A significant increase (P less than 0.01) in the plasma glucose concentration, from 5.2 +/- 0.6 to 6.0 +/- 1.5 mmol . l-1 occurred in the group of subjects drinking the glucose-electrolyte solution. Apart from this, there were no significant differences between the two groups.
mesh_terms: D000328:Adult; D001769:Blood / Q000378:metabolism*; D001786:Blood Glucose / Q000032:analysis; D003681:Dehydration; D004338:Drug Combinations / Q000008:administration & dosage; D004573:Electrolytes / Q000008:administration & dosage; D005947:Glucose / Q000008:administration & dosage; D006400:Hematocrit; D006801:Humans; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance; D012420:Running; D014867:Water / Q000008:administration & dosage; D014882:Water-Electrolyte Balance
chemical_list: D001786:Blood Glucose; C040673:Dioralyte; D004338:Drug Combinations; D004573:Electrolytes; D014867:Water; D005947:Glucose