Fulco C S, Zupan M, Muza S R, Rock P B, Kambis K, Payn T, Hannon M, Glickman E, Cymerman A
Thermal and Mountain Medicine Division, U. S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA.
Int J Sports Med. 2007 May;28(5):437-43. doi: 10.1055/s-2006-924515. Epub 2006 Oct 6.
Recent work from our laboratory demonstrated that carbohydrate supplementation (CHOS) during exercise improved prolonged time-trial (TT) performance of sea-level residents (SLR) living at 4300 m while they were in daily negative energy balance (- 1250 kcal x day (-1); [ ]). The purposes of the current study were to determine during initial exposure to 4300 m:1) whether CHOS also improves TT performance of moderate altitude residents (MAR) who are in energy balance and 2) if acclimatization to moderate elevations benefits TT performance. Fifteen Air Force Academy (AFA) active duty members (age: 30 +/- 1 yrs; mean +/- SE), who had been living at approximately 2000 m for 21 +/- 3 months performed a maximal-effort 720-kJ cycle TT at the AFA and at Pikes Peak (PP), CO, (4300 m) on days 1 (PP1) and 3 (PP3). Daily energy intake and expenditure were maintained similarly at the AFA and PP. At the start of the TTs at PP, and then every 15 min thereafter, 9 subjects drank a 10 % CHO solution (0.175 g x kg (-1) body weight) and 6 subjects drank a placebo (PLA) solution. All subjects were allowed to freely adjust the power output of the cycle ergometer and drank water AD LIBITUM. Performance time did not differ between groups on PP1 (CHOS vs. PLA; 101 +/- 8 vs. 116 +/- 10 min) or PP3 (95 +/- 8 vs. 107 +/- 12 min). For both groups, cycle times on PP1 and PP3 were longer compared to the AFA (p<0.01) and were improved from PP1 to PP3 (p<0.05). Exercise intensity (i.e., % peak oxygen uptake) was maintained similarly at approximately 62 % during the TTs at the AFA and PP. Blood glucose was 1.5 to 2.0 mmol x L (-1) higher for CHOS vs. PLA (p<0.01). It was concluded that CHOS provided no TT performance benefit for MAR at 4300 m when energy balance was maintained. However, the decrements in TT performance and exercise intensity were attenuated at 4300 m in MAR compared to those of SLR as a result of acclimatization attained while living for nearly 2 years at approximately 2000 m.
我们实验室最近的研究表明，运动期间补充碳水化合物（CHOS）可改善生活在4300米处的海平面居民（SLR）在每日能量负平衡（-1250千卡×天-1；[ ]）状态下的长时间计时赛（TT）表现。本研究的目的是确定在初次暴露于4300米时：1）CHOS是否也能改善处于能量平衡状态的中度海拔居民（MAR）的TT表现，以及2）适应中度海拔是否有利于TT表现。15名美国空军学院（AFA）现役成员（年龄：30±1岁；平均值±标准误），他们在约2000米的高度生活了21±3个月，于第1天（PP1）和第3天（PP3）在AFA和科罗拉多州派克峰（PP，4300米）进行了一次竭尽全力的720千焦自行车计时赛。在AFA和PP时，每日能量摄入和消耗保持相似。在PP进行计时赛开始时，以及此后每隔15分钟，9名受试者饮用10%的碳水化合物溶液（0.175克×千克-1体重），6名受试者饮用安慰剂（PLA）溶液。所有受试者可自由调整自行车测力计的功率输出，并可随意饮水。在PP1时，两组的表现时间无差异（CHOS组与PLA组；101±8分钟对116±10分钟），在PP3时也无差异（95±8分钟对107±12分钟）。两组在PP1和PP3时的骑行时间均比在AFA时长（p<0.01），且从PP1到PP3有所改善（p<0.05）。在AFA和PP进行计时赛期间，运动强度（即峰值摄氧量的百分比）相似地维持在约62%。CHOS组的血糖比PLA组高1.5至2.0毫摩尔×升-1（p<0.01）。得出的结论是，当维持能量平衡时，CHOS对4300米处的MAR的TT表现没有益处。然而，由于在约2000米的高度生活了近2年而获得的适应，MAR在4300米处的TT表现和运动强度的下降比SLR的要小。
