title: Caffeine counteracts the ergogenic action of muscle creatine loading.
abstract: This study aimed to compare the effects of oral creatine (Cr) supplementation with creatine supplementation in combination with caffeine (Cr+C) on muscle phosphocreatine (PCr) level and performance in healthy male volunteers (n = 9). Before and after 6 days of placebo, Cr (0.5 g x kg-1 x day-1), or Cr (0.5 g x kg-1 x day-1) + C (5 mg x kg-1 x day-1) supplementation, 31P-nuclear magnetic resonance spectroscopy of the gastrocnemius muscle and a maximal intermittent exercise fatigue test of the knee extensors on an isokinetic dynamometer were performed. The exercise consisted of three consecutive maximal isometric contractions and three interval series of 90, 80, and 50 maximal voluntary contractions performed with a rest interval of 2 min between the series. Muscle ATP concentration remained constant over the three experimental conditions. Cr and Cr+C increased (P < 0.05) muscle PCr concentration by 4-6%. Dynamic torque production, however, was increased by 10-23% (P < 0.05) by Cr but was not changed by Cr+C. Torque improvement during Cr was most prominent immediately after the 2-min rest between the exercise bouts. The data show that Cr supplementation elevates muscle PCr concentration and markedly improves performance during intense intermittent exercise. This ergogenic effect, however, is completely eliminated by caffeine intake.
authors.affiliation: Faculty of Physical Education and Physiotherapy, Department of Kinesiology, Katholieke Universiteit Leuven, Belgium.
authors.forename: K
authors.initials: K
authors.lastname: Vandenberghe
authors.forename: N
authors.initials: N
authors.lastname: Gillis
authors.forename: M
authors.initials: M
authors.lastname: Van Leemputte
authors.forename: P
authors.initials: P
authors.lastname: Van Hecke
authors.forename: F
authors.initials: F
authors.lastname: Vanstapel
authors.forename: P
authors.initials: P
authors.lastname: Hespel
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D002110:Caffeine / Q000009:adverse effects / Q000494:pharmacology*; D003401:Creatine / Q000009:adverse effects / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D004032:Diet; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D007717:Knee / Q000502:physiology; D008297:Male; D018763:Muscle Fatigue / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D010725:Phosphocreatine / Q000378:metabolism; D010726:Phosphodiesterase Inhibitors / Q000009:adverse effects / Q000494:pharmacology*
chemical_list: D010726:Phosphodiesterase Inhibitors; D010725:Phosphocreatine; D002110:Caffeine; D000255:Adenosine Triphosphate; D003401:Creatine