Child Health & Exercise Medicine Program, Room 3N27G, McMaster University, 1280 Main Street West, L8S 4K1, Hamilton, ON, Canada.
Eur J Appl Physiol. 2014 Apr;114(4):707-13. doi: 10.1007/s00421-013-2803-8. Epub 2013 Dec 29.
To evaluate the effect of 1 and 2 % hypohydration on high-intensity cycling performance of 10- to 12-year-old boys in the heat.
In a counterbalanced order, nine boys attended three sessions in which they cycled intermittently (6 × 10-min bouts at 40-45 % [Formula: see text]) in a climate chamber. During each session, environmental conditions and water intake were individually adjusted to achieve a target hypohydration level of 0, 1 or 2 %, based on change in body weight (BW). Following 45 min of rest in thermoneutral conditions when the target hypohydration was maintained, each boy re-entered the climate chamber (35 °C and 50-55 % RH) to perform the cycling performance test at 90 % [Formula: see text] until exhaustion. Heart rate (HR) and rectal temperature (T re) were recorded continuously throughout each session. Total mechanical work (TMW) was taken as a measure of cycling performance.
Actual hypohydration level at the start of the cycling performance test in each session was: 0.1 ± 0.0 %, 1.1 ± 0.1 % and 2.0 ± 0.1 %. With 2 % hypohydration, TMW (35.5 ± 6.8 kJ) was significantly (p < 0.05) lower than with 0 % hypohydration (49.3 ± 9.8 kJ). When expressed as a percentage of TMW with 0 % hypohydration, TMW was reduced by 15.5 and 23.3 % with 1 and 2 % hypohydration, respectively (p < 0.05 for both). At the start of the cycling performance test, HR was 13 and 15 bpm higher, and T re was 0.3 °C higher (p < 0.05 for all) with 1 and 2 % hypohydration, respectively, compared with 0 % hypohydration.
Mild (1 %) to moderate (2 %) hypohydration reduces high-intensity cycling performance of healthy young boys in the heat.
评估 10 至 12 岁男孩在热环境中 1%和 2%脱水对高强度自行车运动表现的影响。
9 名男孩以平衡的方式参加了 3 次实验，他们在气候室内间歇性地进行自行车运动（6 次 10 分钟的冲刺，强度为 40-45%[公式：见正文]）。在每次实验中，根据体重变化（BW），单独调整环境条件和水分摄入，将脱水目标水平设定为 0、1 或 2%。在保持目标脱水水平 45 分钟的休息后，每个男孩在热中性条件下重新进入气候室（35°C 和 50-55%相对湿度），以 90%[公式：见正文]的最大心率进行自行车运动表现测试，直至力竭。在每次实验中，连续记录心率（HR）和直肠温度（T re）。总机械功（TMW）作为自行车运动表现的衡量标准。
在每次实验的自行车运动表现测试开始时，实际脱水水平分别为：0.1±0.0%、1.1±0.1%和 2.0±0.1%。在 2%脱水时，TMW（35.5±6.8kJ）显著低于 0%脱水时（49.3±9.8kJ）（p<0.05）。与 0%脱水时的 TMW 相比，当表示为 TMW 的百分比时，1%和 2%脱水时 TMW 分别降低了 15.5%和 23.3%（两者均为 p<0.05）。在自行车运动表现测试开始时，与 0%脱水相比，HR 分别高 13 和 15 次/分钟，T re 高 0.3°C（均为 p<0.05）。
轻度（1%）至中度（2%）脱水会降低健康年轻男孩在热环境中的高强度自行车运动表现。
