بررسی ابعاد عضله سمی اسپاینالیس کپیتیس و قدرت ایزومتریک عضلات اکستانسور گردن در وضعیت های مختلف در زنان سالم

Background and purpose: Ultrasonography is a reliable and valid method to assess the strength of neck extensors and measuring the neck muscles dimensions. Cervical muscles strength and dimensions may change in different positions. The aim of this study was to compare the strength of cervical extensor muscles and dimensions of semi-spinalis capitis muscle (SECM) in three different neck positions in healthy female individuals. Materials and methods: The research population included 30 female students, 18-24 years of age. Right SECM at the level of third cervical vertebrae was measured by ultrasonography in order to assess the isometric strength of neck extensor muscles in neutral, flexion and extension positions. The size of muscle was calculated by multiplying the anterior-posterior and lateral dimension of the muscle. Afterwards, the muscle strength was measured by a measuring device. One way-ANOVA was used to analyze the data. Results: The SECM size was significantly bigger in extension than that of the neutral and flexion positions (P<0.001). The strength of extensor muscles in neutral position was more than that of the flexion and extension positions. However, there was not a significant correlation between size and strength of the muscle in all three positions. Conclusion: The result of this study indicated that the size of SECM increased in extension position while the strength of neck extensor muscles decreased. The maximum performance of cervical extensor muscles appeared in neutral position of cervical spine, when the muscles were not maximally lengthened or shortened.