Effects of continuous visual feedback during sitting balance training in chronic stroke survivors

Abstract

Background: Postural control deficits are common in stroke survivors and often the rehabilitation programs include balance training based on visual feedback to improve the control of body position or of the voluntary shift of body weight in space. In the present work, a group of chronic stroke survivors, while sitting on a force plate, exercised the ability to control their Center of Pressure with a training based on continuous visual feedback. The goal of this study was to test if and to what extent chronic stroke survivors were able to learn the task and transfer the learned ability to a condition without visual feedback and to directions and displacement amplitudes different from those experienced during training.

Methods: Eleven chronic stroke survivors (5 Male - 6 Female, age: 59.72 ± 12.84 years) participated in this study. Subjects were seated on a stool positioned on top of a custom-built force platform. Their Center of Pressure positions were mapped to the coordinate of a cursor on a computer monitor. During training, the cursor position was always displayed and the subjects were to reach targets by shifting their Center of Pressure by moving their trunk. Pre and post-training subjects were required to reach without visual feedback of the cursor the training targets as well as other targets positioned in different directions and displacement amplitudes.

Results: During training, most stroke survivors were able to perform the required task and to improve their performance in terms of duration, smoothness, and movement extent, although not in terms of movement direction. However, when we removed the visual feedback, most of them had no improvement with respect to their pre-training performance.

Conclusions: This study suggests that postural training based exclusively on continuous visual feedback can provide limited benefits for stroke survivors, if administered alone. However, the positive gains observed during training justify the integration of this technology-based protocol in a well-structured and personalized physiotherapy training, where the combination of the two approaches may lead to functional recovery.

Keywords: Center of pressure; Motor learning; Posture; Stroke survivors; Trunk control; Visual feedback.

Conflict of interest statement

Ethics approval and consent to participate

All procedures were approved by local Institutional Boards (ASL3 Genovese) in accord with the 1964 Declaration of Helsinki.

Consent for publication

Consent provided upon request.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1

Panel a: Experimental set-up; Panel b: Schematic figure of the force platform with four load cells; f1, f2, f3 and f4 are the forces measured by each load cell. 2d =40 cm is the distance between two consecutive load cells. Panel c: Experimental protocol. The circles represent the peripheral targets’ positions on the computer screen; in black is the home target, in grey the three targets presented during the training phase and in white the targets presented only during the pre-training test and post-training test

Fig. 2

Cursor trajectories of a stroke survivor. The first row refers to the initial (first column) and final (second column) performance obtained in the training phase. The second and the third rows refer to the pre-training test (first column) and the post-training test (second column). Specifically, the second row shows the movement in the trained (blue lines) and not trained (red lines) target directions; the third row represents the movement for not trained target displacements

Fig. 3

Changes in performance during training with visual feedback for movement duration (panel a), RE2 (panel b), NJ (panel c), absolute directional error (panel d), NJ2 (panel e) and absolute extent error (panel f). The back lines represent the mean value of each indicator. The shaded areas indicate the standard deviation

Fig. 4

Each bar group represents the performance in the pre-training test (dark grey) and in the post- training test (light grey) for RE2 (panel a), absolute directional error (panel b) and absolute extent error (panel c), without visual feedback, for different displacements and directions of the targets as indicated in the horizontal axis. The height of the bars represents the mean value of the indicators; the error bars correspond to the standard error of the indicators. The dotted lines represent the mean value of the indicator during the last target set of the training phase with continuous visual feedback

Fig. 5

Change in performance during all targets sets of the pre-training test and of the post-training test for RE2 (panel a) and NJ2 (panel b) when the cursor moves in the trained directions. Dark black shaded areas indicate the standard deviation

Fig. 6

The bar group represent the systematic shift (panel a) and the variability (panel b) of the cursor positions when matching the home starting target in the pre-training test (dark grey) and in the post-training test (light grey). The height of the dark bars represents the mean value of the indicators; the error bars correspond to the standard error