Forskning

August 15, 2011

Caffeine intake improves intense intermittent exercise performance and reduces muscle interstitial potassium accumulation

M Mohr et al, Caffeine intake improves intense intermittent exercise performance and reduces muscle interstitial potassium accumulation, Journal of Applied Physiology, 2011.

The effect of oral caffeine ingestion on intense intermittent exercise performance and muscle interstitial ion concentrations was examined. The study consists of two studies  (S1 and S2). In S1 twelve subjects completed the Yo-Yo intermittent recovery level 2  (Yo-Yo IR2) test with prior caffeine (6 mg/kg b.w.; CAF) or placebo (PLA) intake. In  S2 six subjects performed one low intense (20 W) and three intense (50 W) 3-min  (separated by 5 min) one-legged knee-extension exercise bouts with (CAF) and  without (CON) prior caffeine supplementation for determination of muscle interstitial  K+ and Na+ with microdialysis. In S1 Yo-Yo IR2 performance was 16% better  (P<0.05) in CAF compared to PLA. In CAF, plasma K+ at the end of the Yo-Yo IR2  test was 5.2 }0.1 mmol_l-1 with no difference between the trials. Plasma FFA was  higher (P<0.05) in CAF than PLA at rest and remained higher (P<0.05) during  exercise. Peak blood glucose (8.0 }0.6 vs. 6.2 }0.4 mmol_l-1) and plasma NH3 (137.2  }10.8 vs. 113.4 }13.3 umol_l-1) were also higher (P<0.05) in CAF compared to PLA.  In S2 interstitial K+ was 5.5}0.3, 5.7}0.3, 5.8}0.5 and 5.5}0.3 mmol_l-1 at the end of  the 20-W and three 50-W periods, respectively, in CAF which were lower (P<0.001)  than in CON (7.0}0.6, 7.5}0.7, 7.5}0.4 and 7.0}0.6 mmol_l-1, respectively). No differences in interstitial Na+ were observed between CAF and CON. In conclusion,  caffeine intake enhances fatigue resistance and reduces muscle interstitial K+ during intense intermittent exercise.