Yes,torsion(Twist) is an internal force,along with tension(stretch),shear(cut,bend),compression(squeeze).An internal force acts between two parts of something.
External
The noun 'torsion' is a word for the action of twisting or the state of being twisted, especially of one end of an object relative to the other; a word for a thing.
breathing in through your nose is internal, breathing out through your mouth is external.
external force and internal force
Tension, Compression, Shear FOrce, Bending Moment and Torsion
Shear and torsion forces are a combination of bending stress. This stress characterizes the behavior of a structural object subjected to an external load, which is applied perpendicular to the axis of the object.
An internal force is a force acted upon by an object to force another object's movement internally. An external force is a force exerted on an object based on the objects position and force applied on the object which causes the opposite forces change in motion.
Border guards are the element of a security force include the mission of protecting against internal and external threats.
torsion
buthole
A force internal to the system under consideration. Whether a force is regarded as internal or external depends on how the system is defined and classified, and is largely a matter of convenience. In biomechanics, the human body is generally regarded as the system and any force exerted by one part of the body on another is an internal force. Muscle contractions produce internal forces, which move a joint. Compare http://www.answers.com/topic/external-force.