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Subject 1, translational displacements of the head against time: (a) 1 minute of holding still; (b) breath hold; (c) 15 minutes of holding steady; (d) deliberately moving the head. For (a), (b), and (c), all displacements are from the average of the first 10 readings. Graph (d) shows raw data. Dotted grid lines correspond to 1‐mm intervals.
