Dynamic Stability and Trunk Control Improvements Following Robotic Balance and Core Stability Training in Chronic Stroke Survivors: A Pilot Study

Abstract

Stroke survivors show greater postural oscillations and altered muscular activation compared to healthy controls. This results in difficulties in walking and standing, and in an increased risk of falls. A proper control of the trunk is related to a stable walk and to a lower falling risk; to this extent, rehabilitative protocols are currently working on core stability. The main objective of this work was to evaluate the effectiveness of trunk and balance training performed with a new robotic device designed for evaluation and training of balance and core stability, in improving the recovery of chronic stroke patients compared with a traditional physical therapy program. Thirty chronic stroke patients, randomly divided in two groups, either underwent a traditional rehabilitative protocol, or a robot-based program. Each patient was assessed before and after the rehabilitation and at 3-months follow-up with clinical and robot-based evaluation exercises focused on static and dynamic balance and trunk control. Results from clinical scores showed an improvement in both groups in balance and trunk control. Robot-based indices analysis indicated that the experimental group showed greater improvements in proprioceptive control, reactive balance and postural control in unstable conditions, compared to the control group, showing an improved trunk control with reduced compensatory strategies at the end of the training. Moreover, the experimental group had an increased retention of the benefits obtained with training at 3 months follow up. These results support the idea that such robotic device is a promising tool for stroke rehabilitation.

Keywords: balance; core stability; robotic rehabilitation; stroke; trunk control.

Figure 1

(A) Timeline of the experimental procedure. W, week of training; S, training session; T, time of evaluation; T0, before training; T1, after training; T2, 3 months after the end of the training. Each evaluation included clinical assessment and robot-based assessment. Experiment started with the first evaluation (T0), followed by 5 weeks of traditional (control) or robot-based (experimental) rehabilitation. Each week consisted of three sessions of exercises among three categories (steady state, proactive balance or reactive balance). Phase 1 (S1–S5) included steady state and proactive balance exercises; Phase 2 (S6–S10) included steady state, proactive and reactive balance exercises; Phase 3 (S11–S15) included proactive and reactive balance exercises. After training subjects were tested at the end of the program (T1) and at 3 months follow up (T2). (B) Summary of training activities on hunova for the experimental group. Each phase was characterized by different types of exercises that were presented with increasing difficulty. Auditory and visual feedbacks about the accuracy of the performance were continuously provided during the execution of the exercises. Gray-black blocks, different training phases; green blocks, steady state activities; orange blocks, proactive balance activities; red blocks, reactive balance activities.

Figure 2

(A) Prototype of hunova: top view of the platform and seat. The screen was used in both the standing and sitting trials to give visual feedback of the subject's performance. References axis for the feet platform (in red) and seat platform (light blue) are represented. x indicates mediolateral direction, y indicates anteroposterior direction, z indicates vertical direction. (B) Reference system and platform inclinations in different directions (forward, backward, leftward, and rightward).

Figure 3

Clinical scales scores for control (black line) and experimental (gray line) groups. (A) Mini-BESTest; (B) Berg Balance Scale; (C) Trunk Impairment Scale. Error bars indicate Standard Error; * indicate a p-value between 0.01 and 0.05, while ** indicate p < 0.01.

Figure 4

Dynamic balance test on unstable platform. (A) Rate of improvement T0-T1; E, experimental group; C, control group. a: sway area; b: sway path; c: trunk total angular displacement; d: standard deviation of the trunk acceleration. Error bars indicate standard error; * indicates a p-value between 0.01 and 0.05, while ** indicates p < 0.01. (B) Example of platform (rows 1, 3) and trunk (rows 2, 4) angular displacement raw data for two subjects, one from the experimental (gray line) and one from the control (black line) group at T0, T1, T2.

Figure 5

Rate of improvement T0-T1 for the reactive balance test. Each bar plot represents the percentage change of the mediolateral (ML) or anteroposterior (AP) trunk oscillatory range when the platform is inclined in the forward (A), backward (D), affected (C), and non-affected (B) side of the body, for the control (black) and experimental (gray) groups. Error-bars indicate standard error, * highlight a significant difference between groups p < 0.05.

Figure 6

Reaching task results. (A–C) Number of targets reached at T0 and T1 for each subject in the standing (A) or sitting (C) trial. Different colors represent different groups: gray indicates a subject of the experimental group while black represents a subject of the control group. The dashed line represents the line of equality, where the number of targets reached before (T0) and after the treatment (T1) was identical. A data point located above the equality line (in the upper left side of the graph), indicates that a subject reached a bigger number of targets at the end of the treatment T1 than at T0, thus indicating an improvement in movement control. The opposite would hold for a point under the equality line (in the lower right side of the graph). (B–D) Improvement at T1 with respect to T0 in the number of reached targets in a 5-min period computed as T1-T0/T0, respectively in the standing (B) or sitting (D) trial. Error bars indicate Standard Errors; * indicate p < 0.05.

Figure 7

Rate of improvement T0-T1 for the proprioceptive control test. Trunk oscillation changes during the reaching task in standing (first row) and sitting (second row) position are represented. E, experimental group; C, control group. (A–D) Anteroposterior (AP) oscillatory range of the trunk; (B–E): mediolateral (ML) oscillatory range of the trunk; (C–F): standard deviation of the trunk acceleration. Error bars indicate standard error; * indicate a p-value between 0.01 and 0.05, while ** indicate p < 0.01.