McCutcheon L J, Geor R J
Department of Pathobiology, Ontario Veterinary College, University of Guelph, Canada.
Equine Vet J Suppl. 1996 Jul(22):54-62. doi: 10.1111/j.2042-3306.1996.tb05032.x.
The objectives of this study were to: 1) determine incremental and total sweat fluid and ion losses during and following (a) exercise training and (b) a treadmill Speed and Endurance exercise test (SEET) which simulated running speeds and distances required for each phase of an Olympic level (CCI****) 3-day-event in cool and hot ambient conditions and 2) determine the requirement for ion supplementation based on the calculated ion losses associated with these activities. Six exercise-trained Thoroughbred horses completed 2 weeks of exercise training in each of 2 ambient conditions: cool, dry (CD, room temperature [T] = 20-22 degrees C, relative humidity [RH] = 45-55%), or hot and humid (HH, T = 33-35 degrees C, RH = 80-85%). Following the 2 week period of training in either CD or HH conditions, horses completed a SEET under similar conditions (either CD, or hot and dry (HD, T = 33-35 degrees C, RH = 45-55%). Sweating rate and sweat ion composition for each 5 min interval was determined from sweat samples collected from a sealed pouch attached to the lateral thorax. Total sweat fluid losses during training in the heat were 2- or 3-fold greater when compared to CD. Similarly, sweat fluid losses associated with the SEET in HD were almost double (19.2 litres) the losses in CD (11.7 litres). Total calculated ion losses associated with 2 h of training in HH (3724 mmol; 115.2 g) were significantly greater when compared to CD (1413 mmol; 43.5 g). Following the SEET and a 30 min recovery period, total ion losses in CD were 3636 mmol (112.2 g) compared with 6519 mmol (200.6 g) in HD. The differences in ion losses represent the increased sweating rates stimulated by higher core temperatures during moderate to high intensity exercise in warmer ambient conditions and increases in sweat ion concentrations associated with higher sweating rates. Extracellular fluid (ECF) ion losses during daily exercise training and the SEET were also calculated from changes in plasma ion concentrations and ECF volume. Calculated ECF ion losses were significantly higher in hot ambient conditions but were approximately 50% less than calculated sweat ion losses. The calculated sweat ion losses incurred during daily exercise training in hot and humid ambient conditions are > 3-fold higher than losses measured following exercise training in cooler conditions. Whereas fluid regulating hormones may have reduced urinary and faecal losses of ions during 2 weeks of training in HH, the quantity of sodium, potassium and chloride calculated to have been lost in sweat during the SEET in HD exceeded the daily dietary intake of these ions and suggests the need for appropriate ion supplementation during training and competition in hot ambient conditions.
1）确定在（a）运动训练期间及之后，以及（b）跑步机速度和耐力运动测试（SEET）期间及之后的汗液增量和总流失量，该测试模拟了奥运水平（CCI****）3天赛事各阶段在凉爽和炎热环境条件下所需的跑步速度和距离；2）根据与这些活动相关的计算出的离子流失量确定离子补充的需求。六匹经过运动训练的纯种马在两种环境条件下各完成了2周的运动训练：凉爽、干燥（CD，室温[T]=20-22摄氏度，相对湿度[RH]=45-55%），或炎热潮湿（HH，T=33-35摄氏度，RH=80-85%）。在CD或HH条件下进行2周训练后，马匹在类似条件下（CD或炎热干燥[HD，T=33-35摄氏度，RH=45-55%]）完成了SEET。通过从附着在侧胸的密封袋中收集的汗液样本，确定每个5分钟间隔的出汗率和汗液离子成分。与CD相比，炎热环境下训练期间的汗液总流失量增加了2至3倍。同样，HD条件下与SEET相关的汗液流失量几乎是CD条件下（11.7升）的两倍（19.2升）。与HH条件下2小时训练相关的计算出的总离子流失量（3724毫摩尔；115.2克）与CD条件下（1413毫摩尔；43.5克）相比显著更高。在SEET和30分钟恢复期后，CD条件下的总离子流失量为3636毫摩尔（112.2克），而HD条件下为6519毫摩尔（200.6克）。离子流失量的差异代表了在较温暖环境条件下中高强度运动期间较高核心温度刺激出汗率增加，以及与较高出汗率相关的汗液离子浓度增加。还根据血浆离子浓度和细胞外液（ECF）体积的变化计算了日常运动训练和SEET期间的细胞外液离子流失量。炎热环境条件下计算出的细胞外液离子流失量显著更高，但比计算出的汗液离子流失量约少50%。在炎热潮湿环境条件下日常运动训练期间计算出的汗液离子流失量比在较凉爽条件下运动训练后测量到的流失量高3倍以上。虽然在HH条件下2周训练期间，体液调节激素可能减少了尿液和粪便中的离子流失，但在HD条件下SEET期间计算出的汗液中钠、钾和氯的流失量超过了这些离子的每日饮食摄入量，这表明在炎热环境条件下训练和比赛期间需要适当补充离子。
