Investigating the association between sitting ability, trunk electromyography, and sitting posturography in patients with acute stroke: A cross-sectional study.

Background: Sitting ability is an important prognostic factor for patients with acute stroke. However, the characteristics of trunk muscle activity and weight-bearing during sitting are unclear.

Research Question: Are trunk muscle activity and weight-bearing during static sitting associated with sitting ability in patients with acute stroke?

Methods: Trunk electromyography and sitting posturography were performed during static sitting in 20 patients with acute stroke. The electromyography measured the bilateral external oblique and erector spinae muscles. The symmetry of muscle activity between the paralyzed and non-paralyzed side was calculated using the Symmetry Index (SI) raw value and absolute value. The activity of each muscle during static sitting was calculated as the percent reference voluntary contraction (%RVC) normalized by the maximum contraction in the sitting position. Sitting posturography was used to calculate the weight-bearing pressure (%) on the paralyzed and non-paralyzed side, and the raw and absolute values of weight-bearing SI were calculated as a representative value. The trunk impairment scale (TIS) for sitting ability and the Berg balance scale (BBS) for basic balance ability were used as primary outcomes.

Results: None of the SI of electromyography for each trunk muscle correlated significantly with clinical performance tests. The %RVC of paralyzed and non-paralyzed external oblique muscle negatively correlated with TIS. The absolute SI of weight-bearing was negatively correlated with BBS.

Significance: This study showed that the amount, but not the symmetry, of external oblique muscle activity during sitting was associated with sitting ability. We also found that the symmetry of the weight-bearing was associated with sitting ability, not the direction, but the absolute amount of deviation. This suggests that it is important to focus on the amount of external oblique muscle activity and weight-bearing deviation during sitting as a measure of sitting ability in patients with acute stroke.