The passive bending stiffness, tolerable bending moment levels, and el
astic energy storage capabilities of the cervical spine were evaluated
in 40 male and 19 female volunteer subjects from a university student
population, about the flexion, extension, and lateral bending axes. B
ending moments were applied to the neck while subjects lay on a fricti
onless jig and simultaneous angular displacements of the skull relativ
e to the rib cage were recorded. Myoelectric signals from the sternocl
eidomastoid and splenius capitis muscles were amplified over audio spe
akers to train subjects to relax their musculature. Tolerable levels o
f bending moments were quite low (less than 10 N m on average for all
conditions) given the very large magnitude of bending moment applied t
o the neck estimated from impact models. Subjects tolerated greater mo
ment and elastic energy storage in the cervical passive tissues during
flexion than in both extension and in lateral bending. In addition ma
les were able to tolerate larger applied moments, were stiffer, and st
ored more energy than females in all loading conditions. The data deri
ved from this study of loading at very slow rates provide a lower limi
t for bending moments and for cervical spine stiffness, and yield a fi
rst approximation to dynamic bending stiffness values that may be incl
uded in models of the cervical spine.