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The purpose of the present study was to compare mRNA levels of myostatin (MSTN), myogenin (MyoG), and fiber type compositions in terms of myosin heavy chain (MyHC) in skeletal muscles of two rabbit breeds with different body sizes and growth rates. Longissimus dorsi and biceps femoris muscles of 16 Californian rabbits (CW) and 16 Germany great line of ZIKA rabbits (GZ) were collected at the ages of 35d and 84d (slaughter age). The results showed that the live weights of GZ rabbits of 35d and 84d old were approximately 36% and 26% greater than those of CW rabbits, respectively. Quantitative real-time PCR analysis revealed that at the age of 84d GZ rabbits contained significantly lower MSTN mRNA level and higher MyoG mRNA level in both longissimus dorsi and biceps femoris muscles than CW rabbits, and mRNA levels of MSTN and MyoG exhibited opposite changes from the age of 35d to 84d, suggesting that GZ rabbits were subjected to less growth inhibition from MSTN at slaughter age, which occurred most possibly in skeletal muscles. Four types of fiber were identified by real-time PCR in rabbit muscles, with MyHC-1 and MyHC-2D, MyHC-2B were the major types in biceps femoris and longissimus dorsi muscles, respectively. At the age of 84d, GZ rabbits contained greater proportion of MyHC-1 and decreased proportion of MyHC-2D and decreased lactate dehydrogenase activity in biceps femoris than CW rabbits, and the results were exactly opposite in longissimus dorsi, suggesting that GZ rabbits show higher oxidative capacity in biceps femoris muscle than CW rabbits. In conclusion, the trends of mRNA levels of MSTN and fiber types in GZ rabbits' skeletal muscles might be consistent with the putative fast growth characteristic of GZ rabbits compared to CW rabbits.
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http://dx.doi.org/10.1080/10495398.2013.865639 | DOI Listing |
J Biomech
September 2025
Department of Physical Therapy, School of Health Sciences, Sapporo Medical University, Sapporo, Japan; Graduate School of Health Sciences, Sapporo Medical University, Sapporo, Japan. Electronic address:
Understanding the mechanical behavior of the biceps femoris long head (BFlh) may be insightful due to its high susceptibility to strain injuries, particularly during high-speed running in sports, such as soccer and track and field. While prior research has focused on intrinsic muscle properties, emerging evidence suggests that the biceps femoris short head (BFsh) may influence BFlh tension. Thus, we examined the effects of BFsh load application on the tensile strength and regional shear modulus of the BFlh.
View Article and Find Full Text PDFJ Sports Sci
September 2025
Faculty of Health and Sports Science, Doshisha University, Kyoto, Japan.
This study aimed to investigate the acute changes in the passive stiffness of biarticular hamstring muscles after passive stretching and eccentric-only resistance exercise performed at different loads. Thirteen healthy young male participants performed four exercise sessions (on separate days) that comprised passive knee extension (0% of maximal eccentric torque) and eccentric-only knee flexion at different loads (25%, 50% and 75%). Maximal knee joint range of motion, passive torque, shear moduli of the biarticular hamstring muscles, and maximal isometric torque were measured before, 5 min, and 30 min after completing each session.
View Article and Find Full Text PDFRadiol Case Rep
November 2025
Department of Orthopedics and Rehabilitation, Yale School of Medicine, 333 Cedar St. New Haven, CT, 06510, USA.
Hamstring injuries constitute up to 30% of lower-extremity pathology and are the leading cause of time lost from competition in elite athletes. Although hamstring injuries frequently involve the proximal or mid-substance regions, distal injuries are particularly uncommon and are therefore sparsely studied. Among these, biceps femoris tears predominate, whereas those of the semimembranosus and semitendinosus are less common.
View Article and Find Full Text PDFRev Bras Ortop (Sao Paulo)
June 2025
Grupo do Quadril, Departamento de Ortopedia e Traumatologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brasil.
Injuries to the proximal hamstring muscle complex are common in athletes and range from strains to tendinous and bony avulsions. The lesion mechanism typically involves an eccentric contraction of the hamstring muscles during abrupt hip hyperflexion with the knee in extension. Low-speed injuries occur in high kicks and splits, whereas tendon avulsions are common in high-speed activities, such as running and ballet.
View Article and Find Full Text PDFRev Bras Ortop (Sao Paulo)
June 2025
Hip Group, Department of Orthopedics and Traumatology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
Injuries to the proximal hamstring muscle complex are common in athletes and range from strains to tendinous and bony avulsions. The lesion mechanism typically involves an eccentric contraction of the hamstring muscles during abrupt hip hyperflexion with the knee in extension. Low-speed injuries occur in high kicks and splits, whereas tendon avulsions are common in high-speed activities, such as running and ballet.
View Article and Find Full Text PDF