Isometric strength and endurance performance of cervical flexor and extensor muscles were compared in women with (n = 30) and without (n = 30) idiopathic neck pain at the craniocervical and cervicothoracic axes. Strength and endurance time (time to task failure in seconds) at 50% maximal voluntary contraction were recorded in 4 directions (craniocervical flexion/extension and cervicothoracic flexion/extension) and 6 strength and endurance ratios were calculated. Participants in both groups were matched for body mass index. The idiopathic neck pain group demonstrated significantly less strength for the cervicothoracic flexors and extensors (1.58–4.7 N·m [12.4%–17.9%] less, P < .04) and significantly less endurance time for the cervicothoracic and craniocervical flexors (10.77–10.9 s [23.3%–27.5%] less, P < .03). The cervicothoracic extension to craniocervical flexion strength ratio was also lower in the idiopathic neck pain group (P = .01); however, no other strength or endurance ratio was significantly different between groups. This exploratory study suggests assessing specific performance parameters accounting for regional muscular differences in the upper and lower neck is potentially informative to understanding impairments in neck pain conditions, particularly as impairments may not be uniform across muscle groups.
Shaun O’Leary, Carlijn Hoogma, Øystein Molland Solberg, Sara Sundberg, Ashley Pedler and Luke Van Wyk
Shaun O’Leary, Charlotte Loraas Fagermoen, Hiroyuki Hasegawa, Ann-Sofi Slettevold Thorsen and Luke Van Wyk
This study examined isometric strength (maximal voluntary contraction [MVC]) and endurance of cervical flexor and extensor muscles in healthy individuals at the craniocervical (CC) and cervicothoracic (CT) axes. MVC and endurance measures (time to task failure in seconds [s]) at 50% MVC were recorded in 4 directions (CC flexion, CC extension, CT flexion, and CT extension) in 20 males and 20 females, and 6 strength and endurance ratios were calculated. The findings showed that the cervical extensor muscles are not only much stronger than the flexors (1.3–2 times greater MVC), but also have greater capacity for endurance (2–2.4 times greater). While males produced significantly greater MVC recordings than females (P < .003), strength ratios (P > .06) and endurance measures (P > .11) were similar. Endurance ratios were also similar except the CT extension to CC flexion ratio, which was significantly larger in females compared with males (P = .03). These findings demonstrate that substantial but normal variation exists in strength and endurance parameters between cervical flexor and extensor muscles. This is informative to clinicians when evaluating the performance of these neck muscles or when deciding on exercise parameters (eg, load, duration) when training their performance.
Luke Van Wyk, Gwendolen Jull, Bill Vicenzino, Mathew Greaves and Shaun O’Leary
The purpose of this study was to compare maximal torque exerted about the craniocervical (CC) and cervicothoracic (CT) axes in the sagittal plane using a novel dynamometry device. Maximal voluntary contraction (MVC) recordings in newton-meters (N·m) were measured in 20 males and 20 females for each of 4 tests: CT extension, CT flexion, CC extension, CC flexion. Twenty of the volunteers repeated the testing procedure on a second occasion to determine the test–retest repeatability of the measures. MVC recordings at the CT axis (extension, 30.24 ± 12.15 N·m; flexion, 18.90 ± 8.21 N⋅m) were 1.4–2 times greater than recordings at the CC axis (extension, 16.46 ± 7.26 N⋅m; fexion, 13.34 ± 5.97 N·m). Extensor to flexor strength ratios reduced from 1.75 at the CT axis to 1.24 at the CC axis, but were similar for both males and females. Good to excellent test–retest repeatability was demonstrated for all tests (ICC = 0.75–0.99, SEM = 0.50–2.44 N·m). Consistent with differences in the muscle morphology at the CC and CT axes, torque exerted about these axes differ. Separate measurement of torque about these axes potentially offers a more comprehensive profile of cervical muscle strength.
Yaheli Bet-Or, Wolbert van den Hoorn, Venerina Johnston and Shaun O’Leary
Acromion marker cluster (AMC) methods have been shown to accurately track scapula motion during humeral elevation below 90°, however, their accuracy has not been assessed in shoulder girdle motion such as clavicle protraction, retraction, elevation, and depression independent of humeral movement. The aim of this study was to examine the reliability and validity of the AMC method to record scapula orientation at end range clavicle protraction, retraction, elevation, and depression. The right scapulae of 22 female and 20 male asymptomatic volunteers were assessed with an AMC and scapula locator (SL) method during end range clavicle protraction, retraction, elevation, and depression (without humeral elevation) using an 8-camera 3D movement registration system. Measurements recorded from the AMC and SL measures showed fair to excellent agreement (ICC 0.4–0.92). While the AMC method overestimated and underestimated scapular motion in some planes compared to the SL, root mean square error between methods were low for scapular internal/external rotation (2.3–3.7°), upward/downward rotation (4.5–6.6°), and anterior/posterior tilt (3.2–5.1°), across all conditions. The AMC method was shown to be a reliable and valid measurement of scapula orientation at end range clavicle movements independent of humeral movement.