Watson Greig, Casa Douglas J, Fiala Kelly A, Hile Amy, Roti Melissa W, Healey Julie C, Armstrong Lawrence E, Maresh Carl M
The University of Connecticut, Storrs, CT 06269-1110, USA.
J Athl Train. 2006 Jan-Mar;41(1):18-29.
Creatine monohydrate (CrM) use is highly prevalent in team sports (eg, football, lacrosse, ice hockey) and by athletes at the high school, college, professional, and recreational levels. Concerns have been raised about whether creatine use is associated with increased cramping, muscle injury, heat intolerance, and risk of dehydration.
To assess whether 1 week of CrM supplementation would compromise hydration status, alter thermoregulation, or increase the incidence of symptoms of heat illness in dehydrated men performing prolonged exercise in the heat.
Double-blind, randomized, crossover design.
Human Performance Laboratory.
Twelve active males, age = 22 +/- 1 year, height = 180 +/- 3 cm, mass = 78.8 +/- 1.2 kg, body fat = 9 +/- 1%, V(O2)peak = 50.9 +/- 1 ml.kg(-1).min(-1).
INTERVENTION(S): Subjects consumed 21.6 g.d(-1) of CrM or placebo for 7 days, underwent 48 +/- 10 days of washout between treatments, and then crossed over to the alternate treatment in the creatine group. On day 7 of each treatment, subjects lost 2% body mass by exercising in 33.5 degrees C and then completed an 80-minute exercise heat-tolerance test (33.5 degrees C +/- 0.5 degrees C, relative humidity = 41 +/- 12%). The test consisted of four 20-minute sequences of 4 minutes of rest, alternating a 3-minute walk and 1-minute high-intensity run 3 times, and walking for 4 minutes.
Thermoregulatory, cardiorespiratory, metabolic, urinary, and perceptual responses.
On day 7, body mass had increased 0.88 kg. No interaction or treatment differences for placebo versus CrM during the exercise heat-tolerance test were noted in thermoregulatory (rectal temperature, 39.3 +/- 0.4 degrees C versus 39.4 +/- 0.4 degrees C) cardiorespiratory (Vo(2), 21.4 +/- 2.7 versus 20.0 +/- 1.8 ml.kg(-1).min(-1); heart rate, 192 +/- 10 versus 192 +/- 11 beats.min(-1); mean arterial pressure, 90 +/- 9 versus 88 +/- 5 mm Hg), metabolic (lactate, 6.7 +/- 2.7 versus 7.0 +/- 3.0 mmol.L(-1)), perceptual thirst (thirst, 7 +/- 1 versus 7 +/- 1; thermal sensation, 8 +/- 2 versus 8 +/- 1; rating of perceived exertion, 17 +/- 3 versus 17 +/- 2), plasma glucose (0-20 minutes of exercise heat-tolerance, 6.5 +/- 1.2 versus 6.8 +/- 0.8 mmol.L(-1)), plasma (297 +/- 5 versus 300 +/- 4 mOsm.kg(-1)) and urine (792 +/- 117 versus 651 +/- 134 mOsm.kg(-1)), urine specific gravity (1.025 +/- 0.003 versus 1.030 +/- 0.005) and urine color (7 +/- 1 versus 6 +/- 1) measures were increased during CrM. Environmental Symptoms Questionnaire scores were similar between treatments. The levels of dehydration incurred during dehydration and the exercise heat-tolerance test were similar and led to similar cumulative body mass losses (-4.09 +/- 0.53 versus -4.38 +/- 0.58% body mass).
Short-term CrM supplementation did not increase the incidence of symptoms or compromise hydration status or thermoregulation in dehydrated, trained men exercising in the heat.
一水肌酸（CrM）在团队运动（如足球、长曲棍球、冰球）中以及在高中、大学、职业和业余水平的运动员中使用非常普遍。人们对使用肌酸是否会增加抽筋、肌肉损伤、耐热性和脱水风险表示担忧。
评估在炎热环境中进行长时间运动的脱水男性中，补充1周CrM是否会损害水合状态、改变体温调节或增加热疾病症状的发生率。
双盲、随机、交叉设计。
人体性能实验室。
12名活跃男性，年龄=22±1岁，身高=180±3厘米，体重=78.8±1.2千克，体脂=9±1%，最大摄氧量（V̇O₂）峰值=50.9±1毫升·千克⁻¹·分钟⁻¹。
受试者连续7天每天服用21.6克CrM或安慰剂，治疗之间进行48±10天的洗脱期，然后在肌酸组交叉接受替代治疗。在每种治疗的第7天，受试者在33.5摄氏度下运动使体重减轻2%，然后完成一项80分钟的运动耐热性测试（33.5摄氏度±0.5摄氏度，相对湿度=41±12%）。该测试包括四个20分钟的序列，每个序列包括4分钟休息，交替进行3分钟步行和1分钟高强度跑步，重复3次，然后步行4分钟。
体温调节、心肺、代谢、尿液和感知反应。
在第7天，体重增加了0.88千克。在运动耐热性测试期间，安慰剂与CrM之间在体温调节（直肠温度，39.3±0.4摄氏度对39.4±0.4摄氏度）、心肺（V̇O₂，分别为21.4±2.7和20.0±1.8毫升·千克⁻¹·分钟⁻¹；心率，分别为192±10和192±11次·分钟⁻¹；平均动脉压，分别为90±9和88±5毫米汞柱）、代谢（乳酸，分别为6.7±2.7和7.0±3.0毫摩尔/升）、感知口渴（口渴程度，分别为7±1和7±1；热感觉，分别为8±2和8±1；自觉用力程度评级，分别为17±3和17±2）、血浆葡萄糖（运动耐热性测试0至20分钟期间，分别为6.5±1.2和6.8±0.8毫摩尔/升）、血浆（分别为297±
