The influence of goal-directed reaching distance on standing postural control variability in non-disabled individuals

Abstract

BACKGROUND: Performing everyday standing tasks is relevant to the individuals independence. It is a challenging postural action that requires upper extremity (UE) movements to interact with objects of the environment. Postural movement variability is a strategy of the postural system for exploring postural boundaries during the action. The distance to the target to be reached may affect the variability in postural control parameters. AIM: To test if the variability in postural control parameters is enhanced by reaching beyond the UE-length during a goal-directed standing task. METHOD: Twelve non-disabled adult individuals performed reaching to turn on a light switch (target) while standing, which was placed at 100% and 130% of the UE-length distance. The kinetic data were recorded using a force plate during the UE movement, and the centre of pressure (CoP) displacement variability index was calculated. RESULTS: The variability index of the CoP displacement for reaching was greater at the distance of 130% of UE-length compared to 100% in both anterior-posterior and medial-lateral directions (p = 0.019). No differences in time to complete the task were observed. CONCLUSION: Postural system increases the variability in postural controlling variable CoP displacement for reaching beyond the UE-length while standing. This movement variability helps individuals explore the boundaries of this standing action and may be useful for learning processes and counterbalancing postural disturbances.

Shaping Exploration: How Does the Constraint-Induced Movement Therapy Helps Patients Finding a New Movement Solution

“…Maintaining performance close to the participant’s limits seems to be a defining feature of this protocol [ 2 , 29 ]—an argument for its efficacy. Importantly, the possibility of maintaining this level of difficulty was only possible through the use of the RCP [ 30 ]—which is not common even in CIMT.…”

Editorial: The Role of Practice in Motor Skill Acquisition: New Issues, the Same Question

“…That is, how practice can be manipulated to favor or hinder changes in the learner's movement possibilities. Ilha et al 13 , for instance, showed that modification of the task demands/ increase of task difficulty results in increased variability in the system -which was considered as a measure of exploration. This was demonstrated through increased variability in the center of pressure of a standing individual induced by an increase in reaching distance.…”

“…Another interesting point was made by Profeta and Ugrinowitsch 8 in that potential theoretical disputes on what can be transferred comes from the differences from the old to the new situation. Luz, Santos and Bonuzzi 14 , Ilha et al 13 , and Anderson and Steel 16 provided interesting directions on how to optimize the process of search to, first, approximate the solution found during practice to the "maximum" potential performance referred above and, second, how to maximize retention and transfer. In this vein, ideas from Correa et al 6 (see also Profeta and Ugrinowitsch 8 ) on hierarchical systems might provide the theoretical support to understand how (and why) the discussed practice aspects (e.g., attitude, difficulty, distribution, practice schedules) when manipulated can provide better gains in motor learning.…”