title: Investigation of the Differential Contributions of Superficial and Deep Muscles on Cervical Spinal Loads with Changing Head Postures.
abstract: Cervical spinal loads are predominately influenced by activities of cervical muscles. However, the coordination between deep and superficial muscles and their influence on the spinal loads is not well understood. This study aims to document the changes of cervical spinal loads and the differential contributions of superficial and deep muscles with varying head postures. Electromyography (EMG) of cervical muscles from seventeen healthy adults were measured during maximal isometric exertions for lateral flexion (at 10°, 20° and terminal position) as well as flexion/extension (at 10°, 20°, 30°, and terminal position) neck postures. An EMG-assisted optimization approach was used to estimate the muscle forces and subsequent spinal loads. The results showed that compressive and anterior-posterior shear loads increased significantly with neck flexion. In particular, deep muscle forces increased significantly with increasing flexion. It was also determined that in all different static head postures, the deep muscle forces were greater than those of the superficial muscle forces, however, such pattern was reversed during peak efforts where greater superficial muscle forces were identified with increasing angle of inclination. In summary, the identification of significantly increased spinal loads associated with increased deep muscle activation during flexion postures, implies higher risks in predisposing the neck to occupationally related disorders. The results also explicitly supported that deep muscles play a greater role in maintaining stable head postures where superficial muscles are responsible for peak exertions and reinforcing the spinal stability at terminal head postures. This study provided quantitative data of normal cervical spinal loads and revealed motor control strategies in coordinating the superficial and deep muscles during physical tasks.
authors.affiliation: Department of Physical Therapy and Graduate Institute of Rehabilitation Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan, R.O.C.
authors.forename: Chih-Hsiu
authors.initials: CH
authors.lastname: Cheng
authors.affiliation: Department of Physical Therapy and Graduate Institute of Rehabilitation Science, China Medical University, Taichung, Taiwan, R.O.C.
authors.forename: Andy
authors.initials: A
authors.lastname: Chien
authors.affiliation: School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan, R.O.C.|Physical Therapy Center, National Taiwan University Hospital, Taipei, Taiwan, R.O.C.
authors.forename: Wei-Li
authors.initials: WL
authors.lastname: Hsu
authors.affiliation: Department of Physical Medicine & Rehabilitation, Chang Gung Memorial Hospital at Linkou and College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan County, Taiwan, R.O.C.
authors.forename: Carl Pai-Chu
authors.initials: CP
authors.lastname: Chen
authors.affiliation: Graduate Institute of Early Intervention, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan, R.O.C.
authors.forename: Hsin-Yi Kathy
authors.initials: HY
authors.lastname: Cheng
mesh_terms: D000328:Adult; D066193:Cervical Cord / Q000502:physiology; D004576:Electromyography; D005260:Female; D006257:Head / Q000502:physiology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009333:Neck / Q000502:physiology; D064170:Paraspinal Muscles / Q000502:physiology*; D011187:Posture; D013131:Spine / Q000502:physiology*; D064171:Superficial Back Muscles / Q000502:physiology*