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Open Access Research article

Characteristics of myogenic response and ankle torque recovery after lengthening contraction-induced rat gastrocnemius injury

Hongsun Song1, Eisuke Ochi2*, Kihyuk Lee3, Kenji Hiranuma3 and Koichi Nakazato3

Author Affiliations

1 Korea Institute of Sport Science, San223-19, Gongneung-2Dong, Nowon-gu, Seoul, 139-242, South Korea

2 Laboratory of Health and Sports Sciences, Center for Liberal Arts, Meiji Gakuin University, 1518 Kamikurata-cho, Totsuka-ku, Yokohama, Kanagawa, 244-8539, Japan

3 Graduate School of Health and Sport Science, Nippon Sport Science University, 7-1-1, Fukasawa, Setagaya-ku, Tokyo, 158-8508, Japan

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BMC Musculoskeletal Disorders 2012, 13:211  doi:10.1186/1471-2474-13-211

Published: 30 October 2012



Although muscle dysfunction caused by unfamiliar lengthening contraction is one of most important issues in sports medicine, there is little known about the molecular events on regeneration process. The purpose of this study was to investigate the temporal and spatial expression patterns of myogenin, myoD, pax7, and myostatin after acute lengthening contraction (LC)-induced injury in the rat hindlimb.


We employed our originally developed device with LC in rat gastrocnemius muscle (n = 24). Male Wistar rats were anesthetized with isoflurane (aspiration rate, 450 ml/min, concentration, 2.0%). The triceps surae muscle of the right hindlimb was then electrically stimulated with forced isokinetic dorsi-flexion (180°/sec and from 0 to 45°). Tissue contents of myoD, myogenin, pax7, myostatin were measured by western blotting and localizations of myoD and pax7 was measured by immunohistochemistry. After measuring isometric tetanic torque, a single bout of LC was performed in vivo.


The torque was significantly decreased on days 2 and 5 as compared to the pre-treatment value, and recovered by day 7. The content of myoD and pax7 showed significant increases on day 2. Myogenin showed an increase from day 2 to 5. Myostatin on days 5 and 7 were significantly increased. Immunohistochemical analysis showed that myoD-positive/pax7-positive cells increased on day 2, suggesting that activated satellite cells play a role in the destruction and the early recovery phases.


We, thus, conclude that myogenic events associate with torque recovery after LC-induced injury.

Muscle injury; Eccentric contraction; Regeneration; Myogenic factor