Multidirectional neck strength and electromyographic activity for normal controls

Objective. To assess the multidirectional force and indwelling electromyographic activity during maximal effort isometric actions of the neck. Design. A descriptive study involving maximal effort isometric actions of the neck and bilateral electromyographic activity. Background. This study extends previous efforts to assess the isometric strength of the neck, but with greater precision with respect to the intermediate angles between the frontal and sagittal planes. Methodology. Participants (n=18) generated a maximal isometric force in twelve directions in the horizontal plane. All exertions were realized in neutral position. A load cell measured forces and intramuscular fine-wire electrodes were used to record the bilateral electromyographic activity of the sternocleidomastoid, scalenus medius, trapezius (middle fibers), semispinalis capitis, and splenius capitis. Results. Strength in the anterolateral directions were similar, but exhibited right lateral dominance in extension. The sternocleidomastoid and trapezius (middle fibers) exhibited bilateral symmetry while the scalenus medius, semispinalis capitis, and splenius capitis did not. Furthermore, the agonist, synergist, and antagonist action of the individual muscles was clear. The direction of force that resulted in the greatest electromyographic activity was consistent with what has been shown in anatomy texts. This was not true for the scalenus medius. We showed that the scalenus medius contributes to extension, with synergistic activity in the lateral bending direction. Conclusions. The greater precision revealed novel information about the isometric strength of the neck and its musculature.Relevance A detailed study of the multidirectional pattern of force at the neck in able-bodied subjects can serve as a measure of muscle balance, which can be used to establish targets for the therapeutic restoration of neck function.