低水合状态对炎热潮湿环境中乳酸阈的影响。

The effect of the hypohydration on the lactate threshold in a hot and humid environment.

作者信息

Papadopoulos C, Doyle J, Rupp J, Brandon L, Benardot D, Thompson W

机构信息

Applied Physiology Laboratory, Georgia State University, Atlanta, GA, USA.

出版信息

J Sports Med Phys Fitness. 2008 Sep;48(3):293-9.

PMID:18974713

Abstract

AIM

The purpose of this study was to investigate the effect of hypohydration (HH) on the lactate threshold (LT) in a hot and humid environment.

METHODS

Ten apparently healthy males (age 25+/-3 yrs; height 1.8+/-0.04 m; mass 78+/-12 kg; VO2peak 3.7+/-0.4 L/min) underwent four randomly assigned maximal treadmill tests. Two trials were at room temperature (22+/-1 degrees C; RH = 50%) under two different hydration conditions: euhydrated (EH-RM) and hypohydrated (HH-RM), and two trials were performed in a warm chamber (37+/-0.5 degrees C; RH = 70%) under two different hydration conditions: euhydrated (EH-HT) and hypohydrated (HH-HT). The desired HH level (2-4%) was accomplished in the 24+ hours before testing by fluid restriction. Mean HH was 2.6+/-1.0% body weight. Capillary blood samples were collected at the end of each stage and analyzed for lactic acid (LA). LA concentrations were plotted for each exercise stage, and the LT was determined by visual inspection as the highest exercise stage at which blood LA concentration began to increase above each individual's resting levels. LT and body temperature were analyzed with a two-way repeated measures ANOVA (P < 0.05).

RESULTS

During the trials in the warm chamber, the LT occurred at a significantly earlier stage compared to the thermoneutral environment (4.4+/-0.09 vs 5.8+/-0.10) and with a significantly lower oxygen consumption (2.38+/-0.09 L.min(-1) vs 2.86+/-0.13 L.min(-1)). Body temperature at the LT was significantly higher in the heat trials compared to room temperature (38.7+/-0.12 degrees C vs 37.6+/-0.14 degrees C). LT determination was not significantly altered by hydration.

CONCLUSION

These results suggest that during progressive incremental maximal treadmill exercise, moderate HH does not affect the LT, whereas exercise in a hot and humid environment induces a downward shift in the LT. The elevated body temperature during the heat trials suggests that body temperature may affect running performance associated with the LT.

摘要

目的

本研究旨在调查在炎热潮湿环境下轻度脱水（HH）对乳酸阈（LT）的影响。

方法

10名表面健康的男性（年龄25±3岁；身高1.8±0.04米；体重78±12千克；峰值摄氧量3.7±0.4升/分钟）进行了四项随机分配的最大运动平板试验。两项试验在室温（22±1摄氏度；相对湿度=50%）下的两种不同水合状态下进行：水合正常（EH-RM）和轻度脱水（HH-RM），另外两项试验在温暖舱室（37±0.5摄氏度；相对湿度=70%）下的两种不同水合状态下进行：水合正常（EH-HT）和轻度脱水（HH-HT）。在测试前24小时以上通过限制液体摄入达到所需的轻度脱水水平（2-4%）。平均轻度脱水程度为体重的2.6±1.0%。在每个阶段结束时采集毛细血管血样并分析乳酸（LA）。绘制每个运动阶段的LA浓度图，并通过目视检查确定乳酸阈，即血液LA浓度开始高于每个个体静息水平的最高运动阶段。采用双向重复测量方差分析对乳酸阈和体温进行分析（P<0.05）。

结果

在温暖舱室的试验中，与热中性环境相比，乳酸阈出现在显著更早的阶段（4.4±0.09对5.8±0.10），且耗氧量显著更低（2.38±0.09升·分钟-1对2.86±0.13升·分钟-1）。与室温相比，热试验中乳酸阈时的体温显著更高（38.7±0.12摄氏度对37.6±0.14摄氏度）。水合状态对乳酸阈的测定没有显著影响。