Maintained Total Body Water Content and Serum Sodium Concentrations Despite Body Mass Loss in Female Ultra-runners Drinking Ad Libitum during A 100 Km Race

女性長跑者在100公里競賽中自由攝取液體可維持體內水份及血鈉濃度

10.6133/apjcn.2010.19.1.11

Beat Knechtle；Oliver Senn；Reinhard Imoberdorf；Irena Joleska；Andrea Wirth；Patrizia Knechtle；Thomas Rosemann

身體組成 ； 脫水 ； 超耐力 ； 水份 ； 競賽表現 ； body composition ； dehydration ； ultra-endurance ； water ； performance

Asia Pacific Journal of Clinical Nutrition

19卷1期（2010 / 03 / 01）

83 - 90

英文

We investigated in 11 female ultra-runners during a 100 km ultra-run, the association between fluid intake and prevalence of exercise-associated hyponatremia in a cross-sectional study. Athletes drank ad libitum and recorded their fluid intake. They competed at 8.0 (1.0) km/h and finished within 762 (91) min. Fluid intake was 4.1 (1.3) L during the race, equal to 0.3 (0.1) L/h. Body mass decreased by 1.5 kg (p＜0.01); pre race body mass was related to speed in the race (r = -0.78, p＜0.05); and change (Δ) in body mass was not associated with speed in the race. Change in body mass was positively (r = 0.70; p＜0.05), and Δ urinary specific gravity negatively (r = -0.67; p＜0.05), correlated to Δ percent total body water. Changes in body mass were not related to fluid intake during the race. Fluid intake was not correlated to running speed and showed no association with either Δ percent total body water nor Δ [Na] in plasma. Fluid intake showed no relationship with both Δ haematocrit and Δ plasma volume. No exercise-associated hyponatremia occurred. Female ultra-runners consuming fluids ad libitum during the race experienced no fluid overload, and ad libitum drinking protects against exercise-associated hyponatremia. The reported higher incidence of exercise-associated hyponatremia in women is not really a gender effect but due to women being more prone to overdrink.

We investigated in 11 female ultra-runners during a 100 km ultra-run, the association between fluid intake and prevalence of exercise-associated hyponatremia in a cross-sectional study. Athletes drank ad libitum and recorded their fluid intake. They competed at 8.0 (1.0) km/h and finished within 762 (91) min. Fluid intake was 4.1 (1.3) L during the race, equal to 0.3 (0.1) L/h. Body mass decreased by 1.5 kg (p＜0.01); pre race body mass was related to speed in the race (r = -0.78, p＜0.05); and change (Δ) in body mass was not associated with speed in the race. Change in body mass was positively (r = 0.70; p＜0.05), and Δ urinary specific gravity negatively (r = -0.67; p＜0.05), correlated to Δ percent total body water. Changes in body mass were not related to fluid intake during the race. Fluid intake was not correlated to running speed and showed no association with either Δ percent total body water nor Δ [Na] in plasma. Fluid intake showed no relationship with both Δ haematocrit and Δ plasma volume. No exercise-associated hyponatremia occurred. Female ultra-runners consuming fluids ad libitum during the race experienced no fluid overload, and ad libitum drinking protects against exercise-associated hyponatremia. The reported higher incidence of exercise-associated hyponatremia in women is not really a gender effect but due to women being more prone to overdrink.