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Mechanisms underlying enhancements in muscle force and power output during maximal cycle ergometer exercise induced by chronic beta(2)-adrenergic stimulation in men
Univ Copenhagen, Dept Nutr Exercise & Sports, Sect Integrated Physiol, DK-2100 Copenhagen, Denmark.;Bispebjerg Hosp, Dept Resp Res, Copenhagen, Denmark..
Univ Copenhagen, Dept Nutr Exercise & Sports, Sect Integrated Physiol, DK-2100 Copenhagen, Denmark.;Bispebjerg Hosp, Dept Resp Res, Copenhagen, Denmark..
Univ Copenhagen, Dept Nutr Exercise & Sports, Sect Integrated Physiol, DK-2100 Copenhagen, Denmark.;Bispebjerg Hosp, Dept Resp Res, Copenhagen, Denmark..
Univ Copenhagen, Dept Nutr Exercise & Sports, Sect Integrated Physiol, DK-2100 Copenhagen, Denmark.;Bispebjerg Hosp, Dept Resp Res, Copenhagen, Denmark..
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2015 (English)In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 119, no 5, 475-486 p.Article in journal (Refereed) Published
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Abstract [en]

The study was a randomized placebo-controlled trial investigating mechanisms by which chronic beta(2)-adrenergic stimulation enhances muscle force and power output during maximal cycle ergometer exercise in young men. Eighteen trained men were assigned to an experimental group [oral terbutaline 5 mg/30 kg body weight (bw) twice daily (TER); n = 9] or a control group [placebo (PLA); n = 9] for a 4-wk intervention. No changes were observed with the intervention in PLA. Isometric muscle force of the quadriceps increased (P <= 0.01) by 97 +/- 29 N (means +/- SE) with the intervention in TER compared with PLA. Peak and mean power output during 30 s of maximal cycling increased (P <= 0.01) by 32 +/- 8 and 25 +/- 9 W, respectively, with the intervention in TER compared with PLA. Maximal oxygen consumption ((V) over dotO(2)max) and time to fatigue during incremental cycling did not change with the intervention. Lean body mass increased by 1.95 +/- 0.8 kg (P <= 0.05) with the intervention in TER compared with PLA. Change in single fiber cross-sectional area of myosin heavy chain (MHC) I (1,205 +/- 558 mu m(2); P <= 0.01) and MHC II fibers (1,277 +/- 595 mu m(2); P <= 0.05) of the vastus lateralis muscle was higher for TER than PLA with the intervention, whereas no changes were observed in MHC isoform distribution. Expression of muscle proteins involved in growth, ion handling, lactate production, and clearance increased (P <= 0.05) with the intervention in TER compared with PLA, with no change in oxidative enzymes. Our observations suggest that muscle hypertrophy is the primary mechanism underlying enhancements in muscle force and peak power during maximal cycling induced by chronic beta(2-)adrenergic stimulation in humans.

Place, publisher, year, edition, pages
2015. Vol. 119, no 5, 475-486 p.
Keyword [en]
beta-adrenoceptor, Ca2+ handling, contractile properties, muscle growth, doping
National Category
Physiology
Identifiers
URN: urn:nbn:se:miun:diva-26461DOI: 10.1152/japplphysiol.00319.2015ISI: 000360694300007PubMedID: 26159759Scopus ID: 2-s2.0-84942316772OAI: oai:DiVA.org:miun-26461DiVA: diva2:882558
Available from: 2015-12-15 Created: 2015-12-15 Last updated: 2016-01-15Bibliographically approved

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