Meeting Abstract
The axial musculoskeletal core of tetrapods provides a stable base from which limbs exert forces on the environment. The human core is generally thought to be composed of the axial muscles that lie between the diaphragm and pelvic floor and to provide stability for the hindlimbs (i.e., legs). We hypothesized that the human core is actually composed of all the axial muscles extending from the pelvis to the skull. To test whether cervical muscles play a role in core stabilization, we used surface electromyography to measure the activity of a set of neck and jaw muscles during force manipulations of maximum effort counter-movement jumps. To determine whether cervical muscles function during jumps to control posture of the head or to assist in stabilization of the pelvis against the moments applied by the leg retractor muscles we compared muscle activity during control jumps to jumps in which we (1) reduced peak accelerations by approximately 30% by pulling downward on the subject’s hips with elastic tethers, and (2) increased the mass of the head by approximately 100%. When subjects jumped with increased downward force, or with mass added to their heads, maximum and integrated activity of neck and jaw muscles was not different from that recorded during control jumps. 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 neck muscles contribute to core stability in response to moments imposed on the pelvis by the extrinsic muscles of the leg. The observation that neck muscles provide stability for the legs of humans has implications to the locomotor function of the tetrapod neck, prevention of spinal injury, and treatment of chronic cervical and back pain.
