Denadai B S
Departamento de Educação Física, Universidade Esadual Paulista, SP, Brasil.
Braz J Med Biol Res. 1994 Oct;27(10):2481-5.
Several studies have demonstrated that caffeine improves endurance exercise performance but the mechanisms are not fully understood. Possibilities include increased free fatty acid (FFA) oxidation with consequent sparing of muscle glycogen as well as enhancement of neuromuscular function during exercise. The present study was designed to investigate the effects of caffeine on liver and muscle glycogen of 3-month old, male Wistar rats (250-300 g) exercising by swimming. Caffeine (5 mg/kg) dissolved in saline (CAF) or 0.9% sodium chloride (SAL) was administered by oral intubation (1 microliter/g) to fed rats 60 min before exercise. The rats (N = 8-10 per group) swam bearing a load corresponding to 5% body weight for 30 or 60 min. FFA levels were significantly elevated to 0.475 +/- 0.10 mEq/l in CAF compared to 0.369 +/- 0.06 mEq/l in SAL rats at the beginning of exercise. During exercise, a significant difference in FFA levels between CAF and SAL rats was observed at 30 min (0.325 +/- 0.06 vs 0.274 +/- 0.05 mEq/l) but not at 60 min (0.424 +/- 0.13 vs 0.385 +/- 0.10 mEq/l). Blood glucose showed an increase due to caffeine only at the end of exercise (CAF = 142.1 +/- 27.4 and SAL = 120.2 +/- 12.9 mg/100 ml). No significant difference in liver or muscle glycogen was observed in CAF as compared to SAL rats, at rest or during exercise. Caffeine increased blood lactate only at the beginning of exercise (CAF = 2.13 +/- 0.2 and SAL = 1.78 +/- 0.2 mmol/l). These data indicate that caffeine (5 mg/kg) has no glycogen-sparing effect on rats exercising by swimming even though the FFA levels of CAF rats were significantly higher at the beginning of exercise.
多项研究表明，咖啡因可提高耐力运动表现，但其机制尚未完全明确。可能的机制包括增加游离脂肪酸（FFA）氧化，从而节省肌肉糖原，以及增强运动期间的神经肌肉功能。本研究旨在调查咖啡因对3个月大、体重250 - 300克的雄性Wistar大鼠游泳运动时肝脏和肌肉糖原的影响。在运动前60分钟，通过口服插管（1微升/克）给喂食后的大鼠灌胃溶解于生理盐水（CAF）或0.9%氯化钠（SAL）中的咖啡因（5毫克/千克）。大鼠（每组N = 8 - 10只）负重相当于体重5%的重物游泳30或60分钟。运动开始时，CAF组的FFA水平显著升高至0.475±0.10毫当量/升，而SAL组大鼠为0.369±0.06毫当量/升。运动期间，CAF组和SAL组大鼠在30分钟时FFA水平存在显著差异（0.325±0.06对0.274±0.05毫当量/升），但在60分钟时无差异（0.424±0.13对0.385±0.10毫当量/升）。仅在运动结束时，咖啡因使血糖升高（CAF组 = 142.1±27.4，SAL组 = 120.2±12.9毫克/100毫升）。与SAL组大鼠相比，在休息或运动期间，CAF组大鼠的肝脏或肌肉糖原无显著差异。咖啡因仅在运动开始时增加血乳酸（CAF组 = 2.13±0.2，SAL组 = 1.78±0.2毫摩尔/升）。这些数据表明，即使CAF组大鼠在运动开始时FFA水平显著更高，咖啡因（5毫克/千克）对游泳运动的大鼠也没有糖原节省作用。
