title: Inhaled Beta2-Agonist Increases Power Output and Glycolysis during Sprinting in Men.
abstract: OBJECTIVE
  The aim of the present study was to investigate the effects of the beta2-agonist terbutaline (TER) on power output and muscle metabolism during maximal sprint cycling.
  
  
  METHODS
  In a randomized double-blind cross-over design, nine moderately trained men (VO2max = 4.6 ± 0.2 L · min(-1)) conducted a 10-s cycle sprint after inhalation of either 15 mg of TER or placebo (PLA). A muscle biopsy sample was collected before and <10 s after the sprint and was analyzed for metabolites.
  
  
  RESULTS
  The mean power and peak power during the sprint were 8.3% ± 1.1% and 7.8% ± 2.5% higher (P < 0.05) with TER than with PLA, respectively. Moreover, the net rates of glycogenolysis (6.5 ± 0.8 vs 3.1 ± 0.7 mmol glucosyl units · kg dry weight(-1) · s(-1)) and glycolysis (2.4 ± 0.2 vs 1.6 ± 0.2 mmol glucosyl units · kg dry weight(-1) · s(-1)) were higher (P < 0.05) with TER than with PLA. After the sprint, adenosine triphosphate (ATP) was reduced with PLA (P < 0.05) but not with TER. During the sprint, there was no difference in the breakdown of phosphocreatine (PCr) between treatments. Estimated anaerobic ATP utilization was 9.2% ± 4.0% higher (P < 0.05) with TER than with PLA. After the sprint, ATP in Type II fibers was lowered (P < 0.05) by 25.7% ± 7.3% with PLA but was not reduced with TER. Before the sprint, PCr in Type II fibers was 24.5% ± 7.2% lower (P < 0.05) with TER than with PLA. With PLA, breakdown of PCr was 50.2% ± 24.8% higher (P < 0.05) in Type II fibers (vs Type I fibers), whereas no difference was observed between fiber types with TER.
  
  
  CONCLUSIONS
  The present study shows that a TER-induced increase in power output is associated with increased rates of glycogenolysis and glycolysis in skeletal muscles. Furthermore, as TER counteracts a reduction in ATP in Type II fibers, TER may postpone fatigue development in these fibers.
authors.affiliation: 1Respiratory Research Unit, Bispebjerg University Hospital, Copenhagen, DENMARK; 2Section of Integrated Physiology, Department of Nutrition, Exercise, and Sports, University of Copenhagen, Copenhagen, DENMARK; and 3The Swedish School of Sport and Health Sciences, Stockholm, SWEDEN.
authors.forename: Anders
authors.initials: A
authors.lastname: Kalsen
authors.forename: Morten
authors.initials: M
authors.lastname: Hostrup
authors.forename: Karin
authors.initials: K
authors.lastname: Söderlund
authors.forename: Sebastian
authors.initials: S
authors.lastname: Karlsson
authors.forename: Vibeke
authors.initials: V
authors.lastname: Backer
authors.forename: Jens
authors.initials: J
authors.lastname: Bangsbo
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D058666:Adrenergic beta-2 Receptor Agonists / Q000494:pharmacology*; D001642:Bicycling / Q000502:physiology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004734:Energy Metabolism; D006019:Glycolysis / Q000187:drug effects*; D006801:Humans; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D011659:Pulmonary Gas Exchange; D013726:Terbutaline / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D013726:Terbutaline