TY - JOUR
T1 - β2-Adrenergic agonist salbutamol augments hypertrophy in MHCIIa fibers and sprint mean power output but not muscle force during 11 weeks of resistance training in young men
AU - Jessen, Søren
AU - Reitelseder, Søren
AU - Kalsen, Anders
AU - Kreiberg, Michael
AU - Onslev, Johan
AU - Gad, Anders
AU - Ørtenblad, Niels
AU - Backer, Vibeke
AU - Holm, Lars
AU - Bangsbo, Jens
AU - Hostrup, Morten
PY - 2021/3/11
Y1 - 2021/3/11
N2 - In this study, we examined the effect of β 2-agonist salbutamol at oral doses during a period of resistance training on sprint performance, quadriceps contractile function, skeletal muscle hypertrophy, fiber type composition, maximal activity of enzymes of importance for anaerobic energy turnover, and sarcoplasmic reticulum Ca 2+ handling in young men. Twenty-six men (23 ± 2 yr; means ± SD) were randomized to daily intake of oral salbutamol (16 mg/day; RES+SAL) or placebo (RES) during 11 wk of full-body resistance training 3 times/wk. Mean power output during 10-s maximal cycling increased more ( P = 0.027) in RES+SAL (+12%) than in RES (+7%), whereas peak power output increased similarly (RES+SAL: +8%; RES: +7%; P = 0.400). Quadriceps dynamic peak torque and maximal voluntary isometric torque increased by 13 and 14% ( P ≤ 0.001) in RES+SAL and 13 and 13% ( P ≤ 0.001) in RES, respectively. Myosin heavy-chain (MHC) isoform distribution transitioned from MHCI and MHCIIx toward MHCIIa in RES+SAL ( P = 0.002), but not in RES ( P = 0.323). MHCIIa cross-sectional-area increased more ( P = 0.040) in RES+SAL (+35%) than RES (+21%). Sarcoplasmic reticulum Ca 2+ release rate increased in both groups (RES+SAL: +9%, P = 0.048; RES: +13%, P = 0.008), whereas Ca 2+-uptake rate increased only in RES (+12%, P = 0.022) but was not different from the nonsignificant change in RES+SAL (+2%, P = 0.484). Maximal activity of lactate dehydrogenase increased only in RES+SAL (+13%, P = 0.008). Muscle content of the dihydropyridine receptor, ryanodine receptor 1, and sarcoplasmic reticulum Ca 2+-ATPase isoform 1 and 2 did not change with the intervention in either group ( P ≥ 0.100). These observations indicate that the enhancement of sprint mean power output induced by salbutamol is at least partly attributed to greater hypertrophy of MHCIIa fibers and transition toward the MHCIIa isoform. NEW & NOTEWORTHY Here, we show that daily oral treatment with selective β 2-agonist salbutamol induces muscle fiber isoform transition from myosin-heavy-chain (MHC)-I toward MHCIIa and augments hypertrophy of MHCIIa fibers during a period of resistance training. Compared with placebo, salbutamol enhanced sprint mean power output, whereas peak power output and measures of muscle strength increased similarly during the resistance training period despite augmented hypertrophy with salbutamol. Thus, salbutamol is a muscle anabolic drug that can enhance sprint ability adaptations to resistance training.
AB - In this study, we examined the effect of β 2-agonist salbutamol at oral doses during a period of resistance training on sprint performance, quadriceps contractile function, skeletal muscle hypertrophy, fiber type composition, maximal activity of enzymes of importance for anaerobic energy turnover, and sarcoplasmic reticulum Ca 2+ handling in young men. Twenty-six men (23 ± 2 yr; means ± SD) were randomized to daily intake of oral salbutamol (16 mg/day; RES+SAL) or placebo (RES) during 11 wk of full-body resistance training 3 times/wk. Mean power output during 10-s maximal cycling increased more ( P = 0.027) in RES+SAL (+12%) than in RES (+7%), whereas peak power output increased similarly (RES+SAL: +8%; RES: +7%; P = 0.400). Quadriceps dynamic peak torque and maximal voluntary isometric torque increased by 13 and 14% ( P ≤ 0.001) in RES+SAL and 13 and 13% ( P ≤ 0.001) in RES, respectively. Myosin heavy-chain (MHC) isoform distribution transitioned from MHCI and MHCIIx toward MHCIIa in RES+SAL ( P = 0.002), but not in RES ( P = 0.323). MHCIIa cross-sectional-area increased more ( P = 0.040) in RES+SAL (+35%) than RES (+21%). Sarcoplasmic reticulum Ca 2+ release rate increased in both groups (RES+SAL: +9%, P = 0.048; RES: +13%, P = 0.008), whereas Ca 2+-uptake rate increased only in RES (+12%, P = 0.022) but was not different from the nonsignificant change in RES+SAL (+2%, P = 0.484). Maximal activity of lactate dehydrogenase increased only in RES+SAL (+13%, P = 0.008). Muscle content of the dihydropyridine receptor, ryanodine receptor 1, and sarcoplasmic reticulum Ca 2+-ATPase isoform 1 and 2 did not change with the intervention in either group ( P ≥ 0.100). These observations indicate that the enhancement of sprint mean power output induced by salbutamol is at least partly attributed to greater hypertrophy of MHCIIa fibers and transition toward the MHCIIa isoform. NEW & NOTEWORTHY Here, we show that daily oral treatment with selective β 2-agonist salbutamol induces muscle fiber isoform transition from myosin-heavy-chain (MHC)-I toward MHCIIa and augments hypertrophy of MHCIIa fibers during a period of resistance training. Compared with placebo, salbutamol enhanced sprint mean power output, whereas peak power output and measures of muscle strength increased similarly during the resistance training period despite augmented hypertrophy with salbutamol. Thus, salbutamol is a muscle anabolic drug that can enhance sprint ability adaptations to resistance training.
KW - Adrenoceptors
KW - Athletes
KW - Doping
KW - Dynamometer
KW - Kin-com
U2 - 10.1152/japplphysiol.00553.2020
DO - 10.1152/japplphysiol.00553.2020
M3 - Journal article
C2 - 33357007
SN - 8750-7587
VL - 130
SP - 617
EP - 626
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
IS - 3
ER -