King Grub
2018-12-27, 19:02
Du har bara upplevt placebo av koffein före styrkepassen.
INTRODUCTION:
Discrepant results have been reported regarding an intramuscular mechanism underlying the ergogenic effect of caffeine on neuro-muscular function in humans. Here we re-evaluated the effect of caffeine on muscular force production in humans and combined this with measurements of the caffeine dose-response relationship on force and cytosolic free [Ca2+] ([Ca2+]i) in isolated mouse muscle fibers.
METHODS:
Twenty-one healthy and physically active men (29 ± 9 years, 178 ± 6 cm, 73 ± 10 kg, mean ± SD) took part to the present study. Nine participants were involved in two experimental sessions during which supramaximal single and paired electrical stimulations (at 10 and 100 Hz) were applied to the femoral nerve to record evoked forces. Evoked forces were recorded before and 1 h after the ingestion of (i) 6 mg of caffeine per kg of body mass or (ii) placebo. Caffeine plasma concentration was measured in twelve participants. In addition, submaximal tetanic force and [Ca2+]i were measured in single mouse flexor digitorum brevis (FDB) muscle fibers exposed to 100 nM up to 5 mM caffeine.
RESULTS:
Six mg of caffeine per kg body mass (plasma concentration of ~40 µM) did not increase electrically-evoked forces in humans. In superfused FDB single fibers, millimolar caffeine concentrations (i.e. 15 - 35 fold above usual concentrations observed in humans) were required to increase tetanic force and [Ca2+]i.
CONCLUSION:
Our results suggest that toxic doses of caffeine are required to increase muscle contractility questioning the purported intramuscular ergogenic effect of caffeine in humans.
Am J Physiol Cell Physiol. 2018 Dec 19. Toxic doses of caffeine are needed to increase skeletal muscle contractility.
INTRODUCTION:
Discrepant results have been reported regarding an intramuscular mechanism underlying the ergogenic effect of caffeine on neuro-muscular function in humans. Here we re-evaluated the effect of caffeine on muscular force production in humans and combined this with measurements of the caffeine dose-response relationship on force and cytosolic free [Ca2+] ([Ca2+]i) in isolated mouse muscle fibers.
METHODS:
Twenty-one healthy and physically active men (29 ± 9 years, 178 ± 6 cm, 73 ± 10 kg, mean ± SD) took part to the present study. Nine participants were involved in two experimental sessions during which supramaximal single and paired electrical stimulations (at 10 and 100 Hz) were applied to the femoral nerve to record evoked forces. Evoked forces were recorded before and 1 h after the ingestion of (i) 6 mg of caffeine per kg of body mass or (ii) placebo. Caffeine plasma concentration was measured in twelve participants. In addition, submaximal tetanic force and [Ca2+]i were measured in single mouse flexor digitorum brevis (FDB) muscle fibers exposed to 100 nM up to 5 mM caffeine.
RESULTS:
Six mg of caffeine per kg body mass (plasma concentration of ~40 µM) did not increase electrically-evoked forces in humans. In superfused FDB single fibers, millimolar caffeine concentrations (i.e. 15 - 35 fold above usual concentrations observed in humans) were required to increase tetanic force and [Ca2+]i.
CONCLUSION:
Our results suggest that toxic doses of caffeine are required to increase muscle contractility questioning the purported intramuscular ergogenic effect of caffeine in humans.
Am J Physiol Cell Physiol. 2018 Dec 19. Toxic doses of caffeine are needed to increase skeletal muscle contractility.