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

Abstract

Context 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. Objective To evaluate sex differences in US-based muscle size or thickness and biomechanical properties of the cervical-flexor and -extensor muscles. Design Cross-sectional study. Setting Laboratory. Patients or Other Participants 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). Main Outcome Measure(s) 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 t tests or Mann-Whitney U tests were calculated to determine sex differences. The intraclass correlation coefficient (ICC) measured intrarater test-retest reliability. Results Men had thicker SCMs than women (P = .01). No sex differences were present for longus colli cross-sectional area, cervical-extensor muscle thickness, or UT thickness (P > .05). In addition, no sex differences were evident for SCM (P = .302) or UT (P = .703) SWE stiffness. Reliability was good to excellent (ICC = 0.715–0.890) except for SCM SWE stiffness (ICC = 0.554). Conclusions 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.

Sex‐dependent jugular vein optical attenuation and distension during head‐down tilt and lower body negative pressure

“…Myoglobin also absorbs infrared light (Bashkatov et al, 2011 ; Jacques, 2013 ) so the sternocleidomastoid muscle could confound the relationship between absorption signals and IJV blood volume in addition to the effects of hemoglobin. We observed the sternocleidomastoid to be significantly thicker in men compared to women, consistent with previous findings (Nagai et al, 2020 ), and weakly correlated with JVA signal. Importantly, however, while myoglobin within muscle overlying the IJV might contribute to the larger baseline JVA signal in men, it would not account for the greater change in JVA with HDT or LBNP.…”

“…Sex‐based differences in CSA are equivocal (Jeon et al, 2020 ; Magnano et al, 2016 ), although there is some indication that men have larger right IJV than women (Magnano et al, 2016 ), while IJV distensibility appears similar between men and women (Mortensen et al, 1990 ). In contrast, hemoglobin concentrations (Murphy, 2014 ) and sternocleidomastoid muscle volume (Nagai et al, 2020 ) are known to be greater in men. These differences, as well as possible sex differences in CSA, may confound the utility of CHI to monitor IJV blood volume between sexes.…”

“…Coded hemodynamic imaging is currently limited to tracking relative changes in JVA within an individual, while absolute absorption levels will vary due in part to individual differences in hemoglobin, as well as the size and depth of other underlying tissues—attributes with known sex‐specific distributions (Murphy, 2014 ; Nagai et al, 2020 ). Sex‐based differences in CSA are equivocal (Jeon et al, 2020 ; Magnano et al, 2016 ), although there is some indication that men have larger right IJV than women (Magnano et al, 2016 ), while IJV distensibility appears similar between men and women (Mortensen et al, 1990 ).…”

Reliability of Gradient-Echo Magnetic Resonance Elastography of Lumbar Muscles: Phantom and Clinical Studies

“…In sex differences, some previous studies demonstrated that there was a sex difference in muscle stiffness based on ultrasound shear wave elastography, and that males generally had higher muscle stiffness than females [ 30 , 31 , 32 ]. However, the sex differences in muscle stiffness have not been previously evaluated for paraspinal and psoas muscles using the MRE technique.…”

Age-related change in shear elastic modulus of the thoracolumbar multifidus muscle in healthy Beagle dogs using ultrasound shear wave elastography

“…In the young group, the shear elastic modulus of the multifidus muscles at T13 was lower than that at L3. Although the muscle length and CSA of the multifidus muscle were significantly different between T13 and L3, studies in humans showed no significant correlations between muscle mass and muscle stiffness [ 33 40 41 ]. In this study, the elastic shear modulus of the multifidus muscle also showed no change in relation to changes in muscle length or CSA of the multifidus muscle in the adult group.…”