Marathon running: physiological and chemical changes accompanying late-race functional deterioration.
Twenty-one experienced runners were studied before, during and immediately after a marathon race to ascertain whether either depletion of energy substrate or rise in body temperature, or both, contribute to late-race slowing of running pace. Seven runners drank a glucose/electrolyte (GE) solution ad libitum (Na+ 21 mmol l-1, K+ 2.5 mmol l-1, Cl- 17 mmol l-1, PO4(2-) 6 mmol l-1, glucose 28 mmol l-1) throughout the race; 6 drank water and 8 drank the GE solution diluted 1:1 with water. Although average running speeds for the three groups were not significantly different during the first two-thirds (29 km) of the race, rectal temperature was significantly higher (P < 0.05) and reduction of plasma volume was greater (P < 0.05) in runners who replaced sweat losses with water. During the last one-third of the race, the average running pace of the water-replacement group slowed by 37.2%; the pace slowed by 27.9% in the 8 runners who replaced their sweat loss with GE diluted 1:1 with water (1/2 GE) and 18.2% in runners who replaced fluid loss with full-strength solution (GE). Eleven runners (5 in the water group, 4 in the 1/2 GE group and 2 in the GE group) lapsed into a walk/run/walk pace during the last 6 miles of the race. Ten of these had a rectal temperature of 39 degrees C or greater after 29 km of running, and plasma volume in these runners was reduced by more than 10%.(ABSTRACT TRUNCATED AT 250 WORDS)
Cade
R
R
Department of Medicine, University of Florida, Gainesville.
Packer
D
D
Zauner
C
C
Kaufmann
D
D
Peterson
J
J
Mars
D
D
Privette
M
M
Hommen
N
N
Fregly
M J
MJ
Rogers
J
J
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000502:physiology; D001810:Blood Volume / Q000502:physiology; D001831:Body Temperature / Q000502:physiology; D004573:Electrolytes / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D012420:Running; D013546:Sweating / Q000502:physiology
D001786:Blood Glucose; D004573:Electrolytes; D007328:Insulin