No fluid overload in male ultra-runners during a 100 km ultra-run.
We investigated the change in body composition and hydration status in 27 male ultra-runners during a 100 km ultra-run. The athletes drank fluids ad libitum during the run; intake of calories, fluids, and electrolytes during performance were determined. Body mass decreased by 1.9 kg, haematocrit decreased, plasma [Na(+)] remained unchanged, and urinary specific gravity and plasma volume increased. Fluid intake was 0.52 (0.18) L/h and was related to running speed (r = 0.50; p = 0.0081). Δ body mass was associated with total fluid intake during the race (r = 0.49, p = 0.0095). Sodium intake amounted to 425 (478) mg/h and potassium intake to 140 (179) mg/h. Sodium and potassium intake were not related to either postrace concentration or change in plasma concentration. Sodium intake, however, was related to Δ urinary sodium concentration (r = 0.45, p = 0.0227). The increase in plasma volume was significantly and negatively related to both postrace plasma [Na(+)] (r = - 0.42, p = 0.0278) and the postrace potassium-to-sodium ratio in urine (r = - 0.44, p = 0.0218). To conclude, we found no fluid overload in these ultra-runners, the increase in plasma volume was most probably due to a stimulation of the renin-angiotensin-aldosterone system (RAAS) since sodium intake was not related to both the change in plasma [Na(+)] or postrace plasma [Na(+)].
Gesundheitszentrum St. Gallen, St. Gallen, Switzerland. beat.knechtle@hispeed.ch
Beat
B
Knechtle
Oliver
O
Senn
Reinhard
R
Imoberdorf
Irena
I
Joleska
Andrea
A
Wirth
Patrizia
P
Knechtle
Thomas
T
Rosemann
D000328:Adult; D056352:Athletes; D001823:Body Composition / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D003681:Dehydration / Q000503:physiopathology / Q000517:prevention & control; D004326:Drinking / Q000502:physiology*; D006400:Hematocrit; D006801:Humans; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance / Q000502:physiology; D010953:Plasma Volume / Q000502:physiology; D011188:Potassium / Q000097:blood / Q000652:urine; D012420:Running / Q000502:physiology*; D012964:Sodium / Q000097:blood / Q000652:urine; D014882:Water-Electrolyte Balance / Q000502:physiology
D012964:Sodium; D011188:Potassium