Sex Differences in Ultrasound-Based Muscle Size and Mechanical Properties of the Cervical-Flexor and -Extensor Muscles

• Published in: Journal of athletic training 2020-03, Vol.55 (3), p.282-288
• Main Authors: Nagai, Takashi, Schilaty, Nathan D, Krause, David A, Crowley, Eric M, Hewett, Timothy E
• Format: Article
• Language: English
• Subjects: Adult; Athletic Injuries - physiopathology; Biomechanical Phenomena; Biomechanics; Body Composition; Concussion; Control Groups; Correlation; Female; Females; Gender differences; Humans; Ice hockey; Individual Characteristics; Injuries; Male; Males; Measurement Techniques; Muscle Strength - physiology; Neck Muscles - anatomy & histology; Neck Muscles - diagnostic imaging; Neck Muscles - physiology; Neck pain; Neck Pain - physiopathology; Physical Activities; Physical Characteristics; Pregnancy; Reproducibility of Results; Researchers; Sample Size; Scientific Concepts; Sex Characteristics; Spine; Studies; Superficial Back Muscles - anatomy & histology; Superficial Back Muscles - diagnostic imaging; Superficial Back Muscles - physiology; Ultrasonic imaging; Ultrasonography; Women; Young Adult
• ISSN: 1062-6050; 1938-162X
• DOI: 10.4085/1062-6050-482-18

Neck pain (NP), neck injuries, and concussions are more prevalent in female athletes than in their male counterparts. Females exhibit less neck girth, strength, and stiffness against a perturbation. As part of the clinical examination for individuals with NP, ultrasound (US)-based imaging of the cervical muscles has become common. Muscle size or thickness and stiffness can be measured with US-based B-mode and shear-wave elastography (SWE), respectively. Information on reliability, normative values, and sex differences based on US-based muscle size or thickness and stiffness in young and athletic individuals is limited. To evaluate sex differences in US-based muscle size or thickness and biomechanical properties of the cervical-flexor and -extensor muscles. Cross-sectional study. Laboratory. A total of 13 women (age = 23.7 ± 1.9 years, height = 167.1 ± 6.1 cm, mass = 63.8 ± 5.6 kg) and 11 men (age = 25.6 ± 4.9 years, height = 178.7 ± 8.3 cm, mass = 78.9 ± 12.0 kg). The same examiner collected all measures, using US B-mode to scan the cross-sectional area and thickness of the longus colli (LC), sternocleidomastoid (SCM), cervical-extensor muscles, and upper trapezius (UT) muscle. The US SWE-mode was used to measure the stiffness of the SCM and UT. Independent tests or Mann-Whitney tests were calculated to determine sex differences. The intraclass correlation coefficient (ICC) measured intrarater test-retest reliability. Men had thicker SCMs than women ( = .01). No sex differences were present for longus colli cross-sectional area, cervical-extensor muscle thickness, or UT thickness ( > .05). In addition, no sex differences were evident for SCM ( = .302) or UT ( = .703) SWE stiffness. Reliability was good to excellent (ICC = 0.715-0.890) except for SCM SWE stiffness (ICC = 0.554). The only sex difference was in SCM thickness. However, smaller SCMs in women did not result in less SCM SWE stiffness. We provided normative values for US-based imaging of the cervical-flexor and -extensor muscles in young and athletic men and women.