Opposite words for immobility:
sensibility, disturbance, care, frenzy, susceptibility, fury, feeling, agitation, mobility, eagerness, vehemence, sensitiveness, emotion, anxiety, alarm, excitement, violence, distress, sympathy, passion, storm, turbulence.
Usage samples:
  1. In her rage of the previous night she had not seen the wood in its profound immobility.
    "In the Carquinez Woods", Bret Harte.
  2. But its supreme quality was its immobility.
    "The Prelude to Adventure", Hugh Walpole.
  3. Where great immobility is needed, it is one of the most valuable means of restraint we have.
    "Diseases of the Horse's Foot", Harry Caulton Reeks.
  4. Something in the immobility maintained by this figure in face of the quick flashes which from time to time lit up the scene, reminded me of the presence I had come upon hours before in front of Mrs. Carew's house; and moved by the instinct of my calling, I took advantage of the few minutes yet remaining before train time, to make my way in its direction, cautiously, of course, and with due allowance for the possible illumination following those fitful bursts of light which brought everything to view in one moment, only to plunge it all back into the profoundest obscurity the next.
    "The Millionaire Baby", Anna Katharine Green.