Time delays prior to movement alter the drawing kinematics of elderly adults.

Position sense has been found to decay as a function of the time delay the limb remains in a static position prior to movement onset. Position sense has also been found to deteriorate as a function of aging, with increased reliance on vision by the elderly. This study investigated whether the pointing kinematics of elderly adults were differentially affected by delay compared to young adults, and whether visual information could compensate for the effects of delay. Young and elderly adults kept the limb in a static position for 1, 6, or 10 s prior to movement onset, both with and without vision of the limb, initial position, and the movement trajectory. Across groups, delay resulted in increased overall movement duration, decreased peak velocity including a shorter relative time to peak velocity, with decreased distance and duration of the primary submovement. Delay and lack of vision differentially decreased distance of the primary submovement for elderly adults. Vision was able to compensate to some degree for the effects of delay across age groups. The findings provide evidence that decays in position sense as a function of time create difficulties in incorporating the initial limb position in motor planning process in elderly adults.