Age-Related Motor Slowness: Simply Strategic?

BACKGROUND: While older adults typically exhibit slower hesitant movements, this may simply reflect a preference for a cautious movement strategy, rather than any pathological process. METHOD: To separate strategic preferences from any impairment in the coordination of movement, the present experiment trained older adults to move at the preferred speed of younger adults (and vice versa) in a simple zigzag drawing task 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 yrs) joined 9 targets 125 mm apart, of either 5, 10 or 20 mm diameter. Once the age groups were matched for movement duration, movement kinematics were examined to determine whether there were differences in the quality or accuracy of their movements. RESULTS: When strategic differences are controlled for, older adults performed the task with comparable overall accuracy, but exhibited greater hesitancy and more submovements. CONCLUSION: The results suggest a decline in motor coordination rather than any simple strategic preference for caution in movement. The hesitancy of movement to some extent parallels that seen in Parkinson's disease.