Ultrasonographic assessment of transversus abdominis activation during core training tasks and its association with trunk stability in young adults with post-stroke hemiplegia

This study used ultrasound to investigate the acute transversus abdominis (TrA) activation characteristics during core muscle task performance and explore its relationship with trunk stability in young adults with post-stroke hemiplegia. 15 young adults with post-stroke hemiplegia and 22 healthy controls were recruited. Ultrasonography was used to assess TrA thickness and contraction during core muscle training tasks, including quiet and deep exhalation in supine (quiet 0, deep 0) with hips and knees flexed at 90° (quiet 90, deep 90), crunch (crunch 90), and ball-squeezing crunch (ball crunch 90). Correlations between TrA thickness or contraction and trunk stability (Modified Trunk Impairment Scale, mTIS) and activities of daily living (MBI) were examined in patients. 1. Bilateral asymmetry: Healthy controls had a thicker right TrA ( p < 0.001). In left-sided hemiplegia patients, the right TrA was significantly thicker during ball crunch 90 ( p = 0.037). Both groups had bilateral symmetrical contractions (all p > 0.05). 2. Comparison between healthy and patients: Healthy controls had a thicker TrA across all tasks (all p ≤ 0.05) and a higher TrA contraction ratio during deep 0 (left, p = 0.000, right, p < 0.001), while patients demonstrated enhanced contraction during crunch 90 (left, p = 0.005) (right, p = 0.014) and ball crunch 90 (left, p = 0.020, right, p < 0.001). 3. Comparison between different postures: In patients, both crunch 90 and ball crunch 90 yielded significantly higher TrA thickness and contraction ratio than the resting or deep exhalation conditions (all p ≤ 0.05). 4. Correlation with functional performance: Positive trends between functional scales and bilateral TrA metrics were observed in both ambulatory and non-ambulatory patients, but no correlations reached statistical significance. Young adults with post-stroke hemiplegia exhibited right-sided TrA dominance, particularly during the ball crunch 90° task. Among all tested movements, both crunch 90° and ball-crunch 90° elicited the greatest acute TrA activation. Ambulation capacity showed exploratory positive trends in relation to TrA contractility, trunk stability, and activities of daily living. Not applicable.