AGE-RELATED MOTOR SLOWNESS - SIMPLY STRATEGIC

Background. While older adults typically exhibit slower hesitant movem ents, this may simply reflect a preference for a cautious movement str ategy, rather than any pathological process. Method. To separate strat egic preferences from any impairment in the coordination of movement, the present experiment trained older adults to move at the preferred s peed of younger adults (and vice versa) in a simple zigzag drawing tas k on a digitizing tablet which sampled pen position at 200 Hz. Twelve older adults (mean age 69 yrs 8 mo) and 12 young adults (mean age 21 y rs) joined 9 targets 125 mm apart, of either 5, 10 or 20 mm diameter. Once the age groups were matched for movement duration, movement kinem atics were examined to determine whether there were differences in the quality or accuracy of their movements. Results. When strategic diffe rences are controlled for, older adults performed the task with compar able overall accuracy, but exhibited greater hesitancy and more submov ements. Conclusion. The results suggest a decline in motor coordinatio n rather than any simple strategic preference for caution in movement. The hesitancy of movement to some extent parallels that seen in Parki nson's disease.