What do We Plan or Control When We Perform a Voluntary Movement?

  • Gerald L. Gottlieb


The quantitative analysis of multiple degree of freedom movements is a relatively recent practice in motor control. In the early 1980s, Morasso, Lacquaniti, and Soechting published studies of arm reaching that identified certain distinctive kinematic characteristics (Morasso 1981; Soechting and Lacquaniti 1981; Lacquaniti et al. 1982). Morasso noted (p. 224) that “the common features among the different reaching movements are the single-peaked shape of the hand tangential velocity and the [straight] shape of the hand trajectory.” Soechting and Lacquaniti further noted that these properties were unaffected by changes in the load held in the hand or by the intended speed of movement. These properties of straightness and “bell-shaped” velocity profiles have become defining features of unconstrained human reaching movements, even though Hollerbach (1982) noted that movements in the sagittal plane tended to be more curved than those in the horizontal plane.


Equilibrium Point Voluntary Movement Joint Torque Central Command Muscle Torque 
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© Springer-Verlag New York, Inc. 2000

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  • Gerald L. Gottlieb

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