The ability to control fingertip forces at very low levels of force declines with age. Older adults are slower and less accurate (particularly at decreasing force), more heterogeneous, and are usually represented in research studies by wider age ranges. Furthermore, many previous studies were one-session data collections and may not have provided enough practice to evaluate age differences in maximum motor performance. The aim of this study was to determine the effects of age and practice on the control and coordination of fingertip forces on a precision grip isometric tracing task.
Ten adults in each of 3 groups: young (YA, 19-26 yrs); old (OA70, 65-74 yrs); and older (OA80, 75-85 yrs), completed 10 trials on each of 5 days of testing. Performance data were analyzed for time and accuracy for task phase (increasing/decreasing force) and target location (approaching/departing). All groups increased speed and accuracy, and decreased variability (SD) of force tracing with practice (p < .05). The group main effect for time revealed that the YAs were 40% faster than the OA70 group and 70% faster than the OA80 group. The group-by-practice interaction showed that the YA group was faster than the OA80 group by Day 2 but differences between YA and OA70 did not emerge until Day 4. The practice-by-segment interaction revealed that individuals performed 45% slower on segments that involved approaching a target compared with any other segment. Analysis of task phase showed that participants improved only when increasing force (segment 2; p < .05).
All groups demonstrated significant improvements in accuracy following 2 days of practice (p < .01). Additional practice resulted in minimal change however there was a significant difference between Day 2 and 4 (p < .05). Further examination of the reversal and end target proximity regions revealed that all groups traced the template line less accurately and more slowly when approaching a target regardless of whether they were increasing or decreasing force. Indeed, the segment effect was large for all dependent variables, with eta-squared values ranging from .523 to .763. A decrease in variability of time and accuracy did not occur until Day 3 but continued to decrease significantly through Day 5 (p < .05). Practice interacted with target proximity, such that participants were more variable when in segments representing target proximity; approaching the target (p < .05, eta = .891).
The evidence from this study suggests that young and old adults can improve performance with practice, but greater age differences emerge with more practice. In addition, YAs increased accuracy, speed, and consistency of performance throughout the 5 days of practice, and YAs changed sooner and to a greater extent than OAs.