Turn and Reach

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We have previously shown that Coriolis and centripetal forces result when an arm movement is performed during trunk rotation and that these forces produce large trajectory deviations during passive, constant velocity trunk rotation but do not affect movement trajectory during normal, voluntary turn and reach (T&R) movements (Pigeon et al. 2003a,b).

Recently, we studied the accuracy of T&R movements when the generated Coriolis forces were augmented by having the subjects hold a 454g object in their hand. The consequence of holding the weight is to magnify the effect of the Coriolis force by increasing the effective inertial mass of the arm.

We were also interested in whether there would be equal performance for the left and right arm. The results indicated that compensations for forthcoming Coriolis force variations take into account the dynamic properties of the body and of external objects, as well as the planned velocities of the torso and arm (Pigeon et al. 2008).

References
Pigeon P, Bortolami SB, DiZio P, Lackner JR (2003a) Coordinated turn and reach movements. I. Anticipatory compensation for self-generated Coriolis and interaction torques. J. Neurophysiol. 89(1): 276-289.

Pigeon P, Bortolami SB, DiZio P, Lackner JR (2003b) Coordinated turn and reach movements. II. Planning in an external frame of reference. J. Neurophysiol. 89(1): 290-303.

Pigeon P, Lackner JR, DiZio P (2008) Immediate compensation for variations in self-generated Coriolis forces related to body dynamics and carried objects. Soc Neurosci Abstr, 2008.