Smith S A, Montain S J, Matott R P, Zientara G P, Jolesz F A, Fielding R A
Department of Health Sciences, Sargent College of Health and Rehabilitation Sciences, Boston University, Boston, Massachusetts 02215, USA.
J Appl Physiol (1985). 1999 Jul;87(1):116-23. doi: 10.1152/jappl.1999.87.1.116.
Five women and 3 men (29.8 +/- 1.4 yr) performed dynamic knee-extension exercise inside a magnetic resonance system (means +/- SE). Two trials were performed 7-14 days apart, consisting of a 4- to 5-min exhaustive exercise bout. To determine quadriceps cost of contraction, brief static and dynamic contractions were performed pre- and postexercise. (31)P spectra were used to determine pH and relative concentrations of P(i), phosphocreatine (PCr), and betaATP. Subjects consumed 0.3 g. kg(-1). day(-1) of a placebo (trial 1) or creatine (trial 2) for 5 days before each trial. After creatine supplementation, resting DeltaPCr increased from 40.7 +/- 1.8 to 46. 6 +/- 1.1 mmol/kg (P = 0.04) and PCr during exercise declined from -29.6 +/- 2.4 to -34.1 +/- 2.8 mmol/kg (P = 0.02). Muscle static (DeltaATP/N) and dynamic (DeltaATP/J) costs of contraction were unaffected by creatine supplementation as well as were ATP, P(i), pH, PCr resynthesis rate, and muscle strength and endurance. DeltaATP/J and DeltaATP/N were greatest at the onset of the exercise protocol (P < 0.01). In summary, creatine supplementation increased muscle PCr concentration, which did not affect muscle ATP cost of contraction.
5名女性和3名男性（29.8±1.4岁）在磁共振系统内进行动态伸膝运动（均值±标准误）。在7至14天的间隔内进行了两次试验，每次试验包括4至5分钟的力竭性运动 bout。为了确定股四头肌的收缩成本，在运动前和运动后进行了短暂的静态和动态收缩。使用（31）P谱来确定pH值以及无机磷（P(i)）、磷酸肌酸（PCr）和βATP的相对浓度。在每次试验前，受试者连续5天摄入0.3 g·kg-1·天-1的安慰剂（试验1）或肌酸（试验2）。补充肌酸后，静息时的ΔPCr从40.7±1.8增加到46.6±1.1 mmol/kg（P = 0.04），运动期间的PCr从-29.6±2.4下降到-34.1±2.8 mmol/kg（P = 0.02）。补充肌酸对肌肉静态（ΔATP/N）和动态（ΔATP/J）收缩成本没有影响，对ATP、P(i)、pH值、PCr再合成率以及肌肉力量和耐力也没有影响。ΔATP/J和ΔATP/N在运动方案开始时最大（P < 0.01）。总之，补充肌酸增加了肌肉PCr浓度，但不影响肌肉ATP收缩成本。
