Trunk kinematics related to generation and transfer of the trunk flexor momentum are associated with sit-to-stand performance in chronic stroke survivors.

Background: Stroke subjects show poorer sit-to-stand (STS) performance when compared to matched-healthy subjects, but it is still unclear the trunk role in this poorer performance.

Objectives: To compare the trunk kinematics related to the generation/transfer of the flexor momentum during the STS task between stroke and matched-healthy subjects, and to investigate if there were relationships between these variables and STS performance.

Methods: Eighteen chronic stroke survivors and 18 matched-healthy subjects were assessed. The score of the five-repetition STS test and the total/phases duration of the STS (motion analysis system) at both self-selected/fast speeds characterized STS performance. Trunk kinematic variables were maximum forward flexion, peak flexor momentum, and its temporal framework in the STS. Between groups comparisons (Independent Student's t-tests) and correlations (Pearson correlation) were performed (α= 0.05).

Results: Stroke subjects showed poorer STS performance, greater values of maximum forward flexion at fast speeds, and a lower peak flexor momentum at both speeds (0.001≤p≤0.022). In general, the correlations were significant, moderate (0.001≤p≤0.028), and positive to maximum forward flexion (0.37≤r≤0.54) and negative to peak flexor momentum (-0.58≤r≤-0.71).

Conclusions: The poorer STS performance in stroke survivors is associated to the kinematic changes of the trunk related to the poorer ability to generate/transfer the trunk flexor momentum.