Mechanisms underlying enhancements in muscle force and power output during maximal cycle ergometer exercise induced by chronic β2-adrenergic stimulation in men

TY - JOUR

T1 - Mechanisms underlying enhancements in muscle force and power output during maximal cycle ergometer exercise induced by chronic β2-adrenergic stimulation in men

AU - Hostrup, Morten

AU - Kalsen, Anders

AU - Onslev, Johan

AU - Jessen, Søren

AU - Haase, Christoffer

AU - Habib, Sajad

AU - Ørtenblad, Niels

AU - Backer, Vibeke

AU - Bangsbo, Jens

N1 - CURIS 2015 NEXS 315

PY - 2015/9/1

Y1 - 2015/9/1

N2 - The study was a randomized placebo-controlled trial investigating mechanisms by which chronic β2 -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 O2max ) 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 ± 558μm-2 ; P ≤ 0.01) and MHC II fibers (1,277 ± 595 μm2 ; 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 β;-adrenergic stimulation in humans.

AB - The study was a randomized placebo-controlled trial investigating mechanisms by which chronic β2 -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 O2max ) 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 ± 558μm-2 ; P ≤ 0.01) and MHC II fibers (1,277 ± 595 μm2 ; 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 β;-adrenergic stimulation in humans.

U2 - 10.1152/japplphysiol.00319.2015

DO - 10.1152/japplphysiol.00319.2015

M3 - Journal article

C2 - 26159759

SN - 8750-7587

VL - 119

SP - 475

EP - 486

JO - Journal of Applied Physiology

JF - Journal of Applied Physiology

IS - 5

ER -