I chose the vertebra body as target and the disc was chosen as a contact. Because the young's modulus of a vertebra is larger than the disc's young's modulus.
Here, the details of the contacts are given in the photo.
When I initialize the contact tool all the results of information had the orange color legend.
Here is the photo of my model.
I chose the disc of Lumbar 5 as fixed support.
And the force was given on atlas. ( -20 N force was applied in the y-direction).
Here the details of force are given.