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+# The Cervical Spine Model
+
+The cervical spine model is the neck of the human model. It is always present
+when the human model is used.
+
+The cervical spine model contains **7 vertebrae** with 3 DoF spherical
+joints from T1 to C2, a 1 DoF joint between C2 and skull and **136 muscle
+fascicles**. The center of rotations is based on Amevo et al. 1991.
+
+The cervical spine model is part of the Trunk model, and the segments,
+joints and kinematics are therefore included by default.
+
+The segments of the cervical spine model are always present, but the muscles are
+not enabled by default. 
+
+:::{note}
+Some of the neck muscles are defined by the shoulder
+model, so the muscles of the cervical spine model can only be enbled when both
+arms with muscles are present.
+:::
+
+```{raw} html
+<video width="49%" style="display:block; margin: 0 auto;" controls autoplay loop>
+    <source src="../_static/CervicalSpine_rotating_model.mp4" type="video/mp4">
+Your browser does not support the video tag.
+</video>
+<!--<img src="../_static/CervicalSpineCloseupBack.jpg" alt="Smiley face" width="49%">-->
+```
+
+## Example Configuration
+
+Enabling muscles from the cervical spine model, requires that the arms
+also enabled.
+
+:::{seealso}
+:class: margin
+The {doc}`Trunk configuration parameters <../bm_config/trunk>` for a
+full list of Trunk parmaeters.
+:::
+
+```{code-block} AnyScriptDoc
+:emphasize-lines: 4
+
+#define BM_ARM_RIGHT ON
+#define BM_ARM_LEFT ON
+#define BM_ARM_MUSCLE_BOTH ON
+#define BM_TRUNK_CERVICAL_MUSCLES ON
+```
+
+
+
+
+## Resources
+
+More details on the cervical spine can be found online at:
+
+- Thesis: Data on which the cervical spine model, described by [Marike van der
+  Horst](https://pure.tue.nl/ws/files/2084228/200211336.pdf)
+- Webcast: [A detailed rigid-body cervical spine model based on inverse
+  dynamics](https://www.anybodytech.com/em_publication/a-detailed-rigid-body-cervical-spine-model-based-on-inverse-dynamics/)
+
+## References
+
+- de Zee, M., Falla, D., Farina, D. & Rasmussen, J. (2007), "A detailed
+  rigid-body cervical spine model based on inverse dynamics", Journal
+  of Biomechanics, vol. 40 (2), pp. S284.