Training at non-damaging intensities facilitates recovery from muscle atrophy.
Resistance training promotes recovery from muscle atrophy, but optimum training programs have not been established. We aimed to determine the optimum training intensity for muscle atrophy.



Mice recovering from atrophied muscles after 2 weeks of tail suspension underwent repeated isometric training with varying joint torques 50 times per day.



Muscle recovery assessed by maximal isometric contraction and myofiber cross-sectional areas (CSAs) were facilitated at 40% and 60% maximum contraction strength (MC), but at not at 10% and 90% MC. At 60% and 90% MC, damaged and contained smaller diameter fibers were observed. Activation of myogenic satellite cells and a marked increase in myonuclei were observed at 40%, 60%, and 90% MC.



The increases in myofiber CSAs were likely caused by increased myonuclei formed through fusion of resistance-induced myofibers with myogenic satellite cells. These data indicate that resistance training without muscle damage facilitates efficient recovery from atrophy. Muscle Nerve 55: 243-253, 2017.
Physical and Occupational Therapy Program, Nagoya University Graduate School of Medicine, Nagoya, Japan.|Faculty of Rehabilitation Science, Nagoya Gakuin University, Seto, Japan.
Yuta
Y
Itoh
Faculty of Wellness, Shigakkan University, Ohbu, Japan.
Taro
T
Murakami
Physical and Occupational Therapy Program, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Tomohiro
T
Mori
Physical and Occupational Therapy Program, Nagoya University Graduate School of Medicine, Nagoya, Japan.|Faculty of Health and Medical Sciences, Tokoha University, Hamamatsu, Japan.
Nobuhide
N
Agata
Aiche Medical College for Physical and Occupational Therapy, Kiyosu, Japan.
Nahoko
N
Kimura
Aiche Medical College for Physical and Occupational Therapy, Kiyosu, Japan.
Masumi
M
Inoue-Miyazu
Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Kimihide
K
Hayakawa
Faculty of Rehabilitation Science, Nagoya Gakuin University, Seto, Japan.
Takayuki
T
Hirano
Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Masahiro
M
Sokabe
Physical and Occupational Therapy Program, Nagoya University Graduate School of Medicine, Nagoya, Japan.|Faculty of Welfare and Health Sciences, Oita University, Dannoharu 700, Oita City, 870-1192, Japan.
Keisuke
K
Kawakami
D000704:Analysis of Variance; D004558:Electric Stimulation; D005260:Female; D019417:Hindlimb Suspension; D015395:Histocompatibility Antigens Class I / Q000378:metabolism; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D009133:Muscular Atrophy / Q000503:physiopathology / Q000534:rehabilitation*; D017570:MyoD Protein / Q000378:metabolism; D018008:Myogenin / Q000378:metabolism; D051763:PAX7 Transcription Factor / Q000378:metabolism; D020127:Recovery of Function / Q000502:physiology*; D055070:Resistance Training / Q000379:methods*
D015395:Histocompatibility Antigens Class I; D017570:MyoD Protein; D018008:Myogenin; D051763:PAX7 Transcription Factor; C497321:PAX7 protein, human
intensity; isometric contraction; muscle atrophy; recovery; resistance training; torque