Hierarchical control in redundant and non-redundant postural tasks

Prior studies of postural coordination have shown inconsistencies between hip-ankle coordination in redundant and non-redundant coordination tasks as well as predictions of the HKB model. These inconsistencies were investigated by testing the hypothesis that there are different hierarchical control structures for redundant (multiple potential task solutions) and non-redundant (a single task solution) coordination tasks (Bernstein, 1996). The transfer between a non-redundant postural tracking task and a redundant scanning task consisting of 16 hip-ankle relative phase patterns from 0° to 337.5° was investigated. The results showed that the transfer between the tasks was transitory, negative and occurred only from the non-redundant to the redundant task. This finding supports the hypothesis that inconsistencies between redundant and non-redundant coordination dynamics may be due to a hierarchical relation between control structures for the performance of these types of tasks.