Holmes' sign is a test for Hypotonia and Cerebellar Ataxia - dysfunction of the cerebellum region of the brain or connections to it.
The person performing the test (usually a neurologist) asks the person being tested to push a limb (usually one of the legs) against the neurologist's arms. When the neurologist suddenly pulls away his/her arms the signal to stop pushing does not feedback promptly and the muscle does not relax quickly enough. This results in a kick or other rebound movement which is the positive Holmes' sign.
Holmes' sign links: