Training at non‐damaging intensities facilitates recovery from muscle atrophy

• Published in: Muscle & nerve Vol. 55; no. 2; pp. 243 - 253
• Main Authors: Itoh, Yuta, Murakami, Taro, Mori, Tomohiro, Agata, Nobuhide, Kimura, Nahoko, Inoue‐Miyazu, Masumi, Hayakawa, Kimihide, Hirano, Takayuki, Sokabe, Masahiro, Kawakami, Keisuke
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.02.2017
• Subjects: Analysis of Variance; Electric Stimulation; Female; Hindlimb Suspension; Histocompatibility Antigens Class I - metabolism; Humans; intensity; Isometric Contraction; Male; muscle atrophy; Muscle, Skeletal - physiology; Muscular Atrophy - physiopathology; Muscular Atrophy - rehabilitation; MyoD Protein - metabolism; Myogenin - metabolism; PAX7 Transcription Factor - metabolism; recovery; Recovery of Function - physiology; resistance training; Resistance Training - methods; Strength training; torque; intensity; torque; resistance training; muscle atrophy; recovery; isometric contraction
• ISSN: 0148-639X; 1097-4598
• DOI: 10.1002/mus.25218

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