Caffeine ingestion does not alter carbohydrate or fat metabolism in human skeletal muscle during exercise

• DOI: 10.1111/j.1469-7793.2000.00837.x
• Publication Date: 2004-08-12T09:49:58Z
• Authors: Terry E. Graham; Jorn W. Helge; David A. MacLean; Bente Kiens; Erik A. Richter
• Keywords: Glycogenolysis; Respiratory exchange ratio; Carbohydrate Metabolism

1 This study examined the effect of ingesting caffeine (6 mg kg−1) on muscle carbohydrate and fat metabolism during steady-state exercise in humans. Young male subjects (n= 10) performed h (70 % maximal oxygen consumption (V̇O2,max)) two occasions (after ingestion placebo caffeine) leg was quantified by combination direct Fick measures biopsies. 2 Following serum fatty acid glycerol concentration increased (P≤ 0.05) at rest, suggesting enhanced adipose tissue lipolysis. 3 In addition circulating adrenaline rest following this, as well noradrenaline spillover, elevated above values exercise. 4 Caffeine resulted a modest increase vascular resistance, but no difference found blood flow. 5 Arterial lactate glucose concentrations were caffeine, while rise plasma potassium dampened 0.05). 6 There differences respiratory exchange ratio or uptake, net glycogenolysis, release lactate, 6-phosphate concentration. Similarly there between treatments acetyl CoA 7 These findings indicate that stimulated sympathetic nervous system did not alter monitored leg. Other tissues must have been involved changes potassium, acids, lactate.