Postural learning during practice of a sequential reaching task

Anne K. Galgon

doi:10.17918/etd-3143

This research used a motor learning paradigm to examine postural control during practice of a sequential reaching task. Fourteen young healthy adults practiced a sequential (serial) reaching task 300 times over three sessions and returned after a two-day rest interval for retention and transfer testing. Postural control was examined at three levels of skill acquisition: the action, the movement and the neuromotor processing levels. The levels were measured as 1) relative postural stability (action-goal level) with Time to Boundary (TtB) from center of pressure data, 2) postural movement strategies with Mean Absolute Relative Phase (MARP) and Deviation Phase (DP) of joint kinematic relationships, and 3) postural neuromotor strategies with percent of time activation in posterior postural muscles (%BFMG activation). The focal action-goal of the task (hand accuracy and consistency) was also examined to detect differences in explicit versus implicit learning processes. The results showed within and between session differences in hand accuracy and consistency, anterior TtB, and % BFMG activation. Both explicit and implicit learning processes were implicated while acquiring the focal action-goal and more gradual implicit learning processes were used when acquiring the postural action-goal and neuromotor processing level of postural control skill. After the retention interval, hand consistency, relative postural stability and percent of posterior muscle activation was maintained in two recall conditions. However, hand accuracy was retained only in the cued recall condition and not in the free recall condition. Hand accuracy, hand consistency and relative postural stability generalized to two transfer tasks where an alternative arm configuration of the practiced task was performed, however, transfer performance partially degraded in a generalizability test with a novel sequence. Percent of muscle activation was similar in all of the transfer tasks. No significant effects were found for postural movement strategies across practice, which limited the interpretation of the retention and transfer results. This research supports the concept that the postural system is learning to adjust to task specific constraints within the serial reaching task. The findings may have implications for understanding postural learning in individuals with balance deficits and for designing interventions to improve postural control during the performance of functional activities.

Postural learning during practice of a sequential reaching task

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Postural learning during practice of a sequential reaching task

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