Meeting Abstract
Core musculature functions to stabilize the pelvis and trunk against moments imposed by activity of extrinsic limb muscles. Conventionally, the human core is thought to include the axial muscles located between the pelvis and the diaphragm. We suspect, however, that the core includes all of the axial muscles of the trunk and neck. During running, the muscles of the human neck must function to control the posture of the head, but they may also play a role in stabilizing the trunk against the moments imposed on the pelvis by the extrinsic leg muscles. To test if neck muscles play a role in controlling the posture of the head we monitored changes in their activity when subjects ran with 4.5 kg added to their heads, roughly doubling head mass. If activity of neck muscles is required to control head posture, we would expect muscle activity to increase substantially when head mass is doubled. To test whether cervical muscles play a role in core stabilization we increased the fore-aft and vertical forces of running with elastic tethers attached to the subjects via a waist harness. If neck muscles do play a role in core stability, we predict that higher locomotor forces will be associated with elevated cervical muscle activity. We found that when subjects ran at constant speed (2.7 m/s) doubling the mass of the head had little or no effect on the activity of the muscles we monitored. In contrast, alterations of forces imposed on runners in the fore-aft direction resulted in significant changes in cervical muscle activity. These results suggest that superficial cervical muscles act as part of the human core to stabilize the trunk against moments imposed at the pelvis by extrinsic leg muscles during running. 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.
