Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Dystonias ?
    ### Response:
    The dystonias are movement disorders in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures. The movements, which are involuntary and sometimes painful, may affect a single muscle; a group of muscles such as those in the arms, legs, or neck; or the entire body.
    