Research Centre on Aging, University of Sherbrooke, 1036 Belvédère Sud, Sherbrooke, QC, J1H 4C4, Canada.
Eur J Appl Physiol. 2013 Dec;113(12):3011-20. doi: 10.1007/s00421-013-2730-8. Epub 2013 Oct 2.
It has been demonstrated that exercise-induced dehydration (EID) does not impair, and ad libitum drinking optimizes, cycling time-trial (TT) performance. However, the idea that EID ≥ 2 % bodyweight (BW) impairs endurance performance is well ingrained. No study has tested the impact of EID upon running TT performance. We compared the effects of thirst-driven (TD) vs. programmed fluid intake (PFI) aimed at maintaining EID-associated BW loss <2 % on half-marathon performance.
Ten trained distance runners underwent, in a randomized, crossover fashion, two, 21.1 km running TTs on a treadmill (30 °C, 42 % relative humidity) while facing a wind speed matching running speed and drinking water (1) according to thirst sensation (TD) or (2) to maintain BW loss <2 % of their pre-exercise BW (PFI), as recommended by the American College of Sports Medicine.
Despite that PFI significantly reduced EID from 3.1 ± 0.6 (TD) to 1.3 ± 0.7 % BW (PFI), mean rectal temperature from 39.4 ± 0.4 to 39.1 ± 0.3 °C, mean body temperature from 38.1 ± 0.4 to 37.7 ± 0.2 °C and mean heart rate from 175 ± 9 to 171 ± 8 bpm, neither half-marathon time (TD 89.8 ± 7.7; PFI 89.6 ± 7.7 min) nor running pace (TD 4.3 ± 0.4; PFI 4.2 ± 0.4 min/km) differed significantly between trials.
Albeit providing trivial cardiovascular and thermoregulatory advantages, in trained distance runners, PFI (1,380 ± 320 mL/h) offers no performance benefits over TD fluid intake (384 ± 180 mL/h) during a half-marathon raced under warm conditions.
已经证明，运动引起的脱水（EID）不会损害，并且随意饮水可以优化计时赛（TT）的表现。然而，EID≥2%体重（BW）会损害耐力表现的观点已经深入人心。没有研究测试过 EID 对跑步 TT 表现的影响。我们比较了口渴驱动（TD）与编程液体摄入（PFI）的影响，旨在保持 EID 相关的 BW 损失<2%对半程马拉松表现的影响。
10 名经过训练的长跑运动员以随机交叉方式在跑步机上进行了两次 21.1 公里的跑步 TT（30°C，42%相对湿度），同时面对与跑步速度相匹配的风速，并根据口渴感（TD）或（2）按照美国运动医学学院的建议，保持 BW 损失<2%的预运动 BW（PFI）来饮水。
尽管 PFI 显著减少了 3.1±0.6%（TD）至 1.3±0.7% BW（PFI）的 EID，但直肠温度从 39.4±0.4°C 降至 39.1±0.3°C，平均体温从 38.1±0.4°C 降至 37.7±0.2°C，平均心率从 175±9 bpm 降至 171±8 bpm，但半程马拉松时间（TD 89.8±7.7；PFI 89.6±7.7 分钟）和跑步速度（TD 4.3±0.4；PFI 4.2±0.4 分钟/公里）在两次试验之间均无显著差异。
在训练有素的长跑运动员中，尽管 PFI（1380±320 mL/h）提供了微不足道的心血管和体温调节优势，但在温暖条件下进行半程马拉松比赛时，PFI 提供的性能优势并不优于 TD 液体摄入（384±180 mL/h）。
