Meeting Abstract
The musculoskeletal core provides a stable base that allows limbs to exert forces on the environment. We hypothesized that the human core is actually a musculoskeletal loop that begins at the pelvis on one side of the body and extends cranially, via active muscles, to the skull and then extends caudally down the opposite of the neck and trunk. To test whether or not the neck is part of the core we used surface electrodes to measure the activity of a set of cervical and trunk muscles during maximum effort counter-movement jumps. To determine whether cervical muscle activity during jumps function to control posture of the head and/or function to assist in stabilization of the trunk against the moments applied to the pelvis by the leg retractor muscles we compared muscle activity during control jumps to jumps in which we (1) increased the mass of the head by 20%, and (2) reduced peak accelerations by approximately 10% by pulling downward on the subject’s hips with elastic tethers. When subjects jumped with mass added to their heads, changes in muscle activity varied from subject to subject and no consistent pattern was observed. When subjects jumped with increased vertical force, to reduce acceleration, activity increased significantly in both the strap (i.e., sternohyoid and sternocleidomastoid) and epaxial (i.e., semispinalis) muscles. These results do not support the hypothesis that the superficial muscles of the neck (i.e., those accessible with surface electrodes) play an important role in postural support of the head during active movement. Instead, our results suggest that these cervical muscles contribute to core stability in response to moments imposed on the pelvis by the extrinsic muscles of the leg. These results have implications to the locomotor function of the tetrapod neck and to the prevention of spinal injury.
