Postural influence on Stand-to-Sit leg load sharing strategies and sitting impact forces in stroke patients

Postural configurations for stroke patients in performing Stand-to-Sit (StandTS) were thought identical to those in performing Sit-to-Stand. The specificity of StandTS in terms of leg load sharing and sitting impact forces is however largely unexplored. The objective of this research was to study how the two legs share loads and sitting impact forces in stroke patients during StandTS movements with different postural configurations. It was hypothesized that adopting different arm placements combined with leg placements would alter the leg load sharing and subsequently influence the sitting impact on stroke patients. This hypothesis was tested on 18 elder hemiplegic stroke patients with four postural configurations of arm and leg placements. Results showed that altering arm placements does not significantly influence the leg load sharing strategy and sitting impact forces. The leg load sharing strategies are ruled by the preferred use of the non-paretic side and the favored leg position for the biomechanical load. Placing the non-paretic leg posterior reduces the impact because of the advantage of the preferred use together with the favored leg position. Because the paretic leg is incapable of modulating the sitting-down process, placing the paretic leg posterior induces notably greater sitting impact forces compared with the counter leg placement. From the strength-training point of view, however, placing the paretic leg posterior would facilitate exertions of the paretic leg.