Age-related motor slowing may result from abnormal trajectory formation. Curved trajectories can be described by a 1/3 power law linking velocity and radius of curvature. As a basic coordinative principle that emerges with maturation, factors producing any variation in this relationship may thus provide insights into age-related changes in the coordination of movement. The authors determined whether variations in the fit of a 1/3 power law with advancing age were associated with temporal or postural constraints. Young and older adults moved under temporal (speed and timing cues) or postural (joint combinations used) constraints, while performing elliptical movements upon a graphics tablet at 1 or 2 Hz. A 1/3 power law was influenced by variations in speed and the joint combinations employed, but reductions off it were not necessarily linked to force inefficiency. Age-related reductions in the strength of a 1/3 power law were a function of postural constraints.
Saling, L., & Phillips, J. G. (2002). Age-related changes in the kinematics of curved drawing movements: Relationships between tangential velocity and the radius of curvature. Experimental Aging Research, 28(2), 215-229. https://doi.org/10.1080/03610730252800210