Chapter 2. Prehension

168 THE PHASES OF PREHENSION
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I
100
Figure 1 Grasping for a dowel 2.5 cm in diameter with ,-d
opposition, using independent fingers (I) or palm opposition using
collective fingers (C). A. Representative resultant velocity profile
for wrist IRED marker from one subject B. Acceleration profile of
wrist marker, derived from differentiating the tangential velocity
profile. C. Aperture evolution for Collective and Independent
finger grasps. Note the larger aperture for collective finger
movements, even though both grasp types were used for the same
sized dowel. Note the greater time spent in the deceleration phase
with independent finger movements in pad opposition, compared to
collective finger movements in palm opposition (from Sivak,
1989; reprinted by permisssion).
I
100