Abstract
Objective: Several strategies have been designed to improve balance after stroke. Although recent studies have suggested that the balance training in stroke should include exercises that are performed in different sensory conflict conditions, little attention has been paid to manipulation of visual input. This study aimed to compare effects of balance training on an unstable surface with balance training under visual deprivation conditions in persons with stroke. Method: Forty-five stroke patients were randomized into three groups: the visual deprivation- stable based training (VD-SBT); unstable based training (UBT); and control (C) groups. Subjects of the VD-SBT group performed balance training on a stable surface with closed eyes. The UBT group performed balance training on an unstable surface with open eyes. Patients were assessed before and after interventions for Timed Up and Go (TUG), Four Square Step (FSS) and Five Times Sit to Stand (FTSS) tests. Result: There was a significant difference in pre- post intervention time of TUG, FSS and FTSS tests in all three groups. In a comparison of three groups, the UBT and VD-SBT groups had a significant improvement in time of all tests but significant improvement in time of all tests was observed in the VD-SBT group in comparison with the UBT group. In the field of balance training, the manipulation of visual input was more effective than the manipulation of standing surface to reweighting the sensory information. Conclusion: We recommended balance rehabilitation programs after stroke performed under conditions to stimulate the use of underused sensory input.
Keywords: Balance training, Stroke, Sensory integration, Visual deprivation
Stroke is a condition that happens when blood circulation in some parts of the brain is interrupted as a results of blockage in blood stream or hemorrhage event1). Based on the World Health Organization (WHO) report, stroke has the second place among diseases causing death worldwide2) and causing long-term disability for patients3). The majorities of people with stroke have some degree of balance and gait impairment. Balance impairment owing to paralysis and muscle weakness in lower limbs is one of the main determinants associated with falls and restricted activities of daily living after stroke.
Control of balance needs the involvement of different parts of the brain and spinal cord4). Sensory inputs from vestibular system and proprioceptors are necessary for postural control and balance which are used by different parts of the brain and spinal cord to provide a good balance5). In a neurologically normal participant, these systems act together to build a multisensory integration system for adjusting balance; as a result, when a sensory input from one of these systems decreases, the central integration resolves sensory conflict and selects an appropriate information from disparate sensory input to achieve the best result in controlling the balance6). Impaired somatosensory integration in stroke patients has been reported in several studies7-9). Several therapeutic strategies are designed to improve balance by manipulation of these three systems. Perturbation training10), training on unstable surface11) and weight shift training12) are designed interventions for enhancing the balance ability in stroke patients to use the proprioception. Visual feedback and visual deprivation training are two different methods of visual input manipulation that are used as a therapeutic approach to improve balance reactions13,14). Visual feedback therapy is able to gain a symmetrical stance15) and improve sitting balance and visual perception13) after the stroke, but there are evidence that visual feedback therapy has no additional effect on the conventional therapy16). Previous studies showed that persons with stroke are significantly rely on their vision to compensate for the decreased function of the other involved sections for improving their balance7,17). Therefore, they suggest that the balance training for patients with chronic stroke should include practicing with different sensory conditions to make it challenging enough for nervous system to improve its ability to increase balance. Despite a great number of studies on the unstable base training and visual deprivation training by stroke patients, such programs have not been compared yet. Therefore, the aim of current study is to compare the effects of balance exercise on unstable base with balance exercise under visual deprivation conditions in stroke patients.
Methods
1 Participants
This was a randomized clinical trial with concealed allocation. Patients on the physiotherapy clinic of Loghman hospital, university of Shahid Beheshti medical sciences, Iran were approached for participation. Patients who expressed interest in participating in the study were screened for the following inclusion criteria: First ever stroke; at least 6 months after stroke; ability to walk at least 10 m without assistance. We excluded individuals with sever cognitive problems; neurological disease and musculoskeletal conditions preventing participation in rehabilitation program. The study protocol was approved by ethics committee of Shahid Beheshti University of medical sciences (No: IR.SBMU.RETECH.REC.1398.819). Participants provided written informed consent after receiving full information about the goals and process of study. Following consent, patients were randomized using a computer-generated block randomizer to 1 of 3 groups: The visual deprivation- stable based training (VD-SBT); unstable based training (UBT); and control (C) groups. Sealed envelopes opaque were used for allocation concealment. The sealed envelope was opened by the researcher exactly before the intervention. The assessor and data analyst did not know how the subjects were allocated. The sample size was calculated based on BBS data reported by Combs et al.18) We used the effect size (0.53) of the BBS for calculation. A sample size of 15 participants in each of the 3 groups was needed to achieve a power of 0.80 at α level of 0.05. The study was registered at the Iranian Registry of Clinical Trials (IRCT) (http://www.irct.ir, registration reference: IRCT20190812044516N1).
2 Intervention
All groups received general physical therapy exercise including muscle stretching and strengthening exercise that was specific for each patient by a train researcher. Participants in the VD-SBT group were instructed to perform balance training exercise on a firm floor while they are keeping their eyes closed. The balance training program consisted of Weight shifting; toe/heel rising; heel/toe standing and one leg standing exercise19,20) (Table 1). The UBT group performed balance training on a firm foam (balance pad: Mambo balance pad 37, 22, 6 cm Europe bvba) with open eyes. Fig. 1 summarize the balance exercises that performed by the UBT group. Subjects in the control group received general physiotherapy exercise. Each exercise session consisted of 4 sets in 30 minutes with one minute of rest interval between each set. The interventions were carried out for one month, 3 sessions per week in the stroke rehabilitation center.
Table 1.
Balance training protocol
| Weight shifting exercise with feet parallel together | |
| a. Weight shift side to side | |
| b. Weight shift heel to toe | |
| Toe raise | |
| a. Standing with feet hip-width apart slowly lift the front of feet | |
| b. Standing with feet hip-width apart slowly lower the front of feet | |
| Weight shifting exercise with feet in half tandem | |
| a. Weight shift side to side | |
| b. Weight shift heel to toe | |
| Heel raise | |
| a. Standing with feet hip-width apart slowly lift up the heel | |
| b. Standing with feet hip-width apart slowly lower the heel | |
| Heel toe standing | |
| a. Standing with paretic foot in front of the sound foot for 10 -20 seconds | |
| b. Standing with paretic sound foot in front of the paretic foot for 10-20 seconds | |
| One leg standing | |
| a. Standing on sound leg without holding onto the counter for 10 seconds | |
| b. Standing on the paretic legwithout holding onto the counter for 10 seconds | |
Fig. 1.
Participant in the UBT group performing balance training on a balance pad: (a) Weight shift side to side. (b) Heel raises (c) Toe raises (d) One leg standing.
3 Outcome Measures
Participants completed the Timed Up and Go (TUG), Four Square Step (FSS) and Five Times Sit to Stand (FTSS) tests at baseline and after completing their intervention. The dynamic balance during walking was assessed by TUG21). To do this test, patients were asked to stand up from a seat (using armrests, if necessary), walk towards a cone that is 3 meters far away from the seat, turn around, walk back to the seat and sit back down on the seat. Dynamic standing balance was assessed by the FSS test22). The Four Square Step Test is a valid clinical test of dynamic standing balance23). This test could show whether the patient is able to a step over an object in different directions or not (forward, sideways and backward). During FTSS test, patients instructed to stand up straight and sit down 5 times as quickly as they could. This ability relies on the lower extremity proprioception24), dynamic balance and their general mobility25).
4 Data analysis and statistics
The average time of all test trials were calculated. All the data were analyzed by SPSS18.0 for Windows (SPSS Inc., Chicago, IL, USA). Descriptive statistics and test of normality using the Shapiro-Wilk test was performed on all outcome variables. The means of subject characteristics across groups were compared using 1-way analysis of variance (ANOVA). The paired t-test was used to examine the difference between pre and post-treatment in each group. The difference on the type of therapy among the 3 groups were assessed by using two-way repeated-measures analysis of variance (ANOVA) with time (pre, post intervention) and group (VD-SBT, UBT, control) as factors for each of post-training scores (TUG, FSS, TUG ). The Tukey HSD was used as the post hoc analyses. For all analyses, statistical significance was set at P < 0.05.
Results
The study began with an initial screening of 60 individuals, 15 were excluded, and 45 were finally chosen on the basis of inclusion criteria and were enrolled in the study (Fig. 2). All participants completed the intervention and assessments. Of the 45 subjects in the study, 26(60%) had the right side of body affected. The time after the onset of stroke was a minimum of 6 months and a maximum of 2 years with average duration of 14.6 ±9.2 months. No significant difference was observed in time from stroke onset (p = 0.72), among the three groups. Table 2 presents general characteristics of all groups. No significant differences were found in terms of age, height, weight and side of stroke between all groups. Table 3 revealed the values of all outcome measures before and after intervention.
Fig. 2.
Flow diagram of the study participants.
Table 2.
The general characteristics of the study participants.
| VD-SBT (n=15) | UBT (n=15) | Control (n=15) | P | |
|---|---|---|---|---|
| NOTE: Values are mean ± standard deviation (SD) or number. M/F: Male/Female; VD-SBT: visual deprivation-stable based training; UBT: unstable base training; Rt/lt: Right/Left; P*≤0.05 | ||||
| Gender (M/F) | 7/8 | 9/6 | 8/7 | 0.88 |
| Age (years) | 67.2±9.6 | 68.8±8.9 | 67.5±9.9 | 0.69 |
| Time since stroke onset (months) | 15.4±4.7 | 14.4±4.5 | 14±6.3 | 0.72 |
| Weight (Kg) | 79.9±7.4 | 81.2±8.6 | 79.2±8.7 | 0.81 |
| Height (cm) | 167.9±8.7 | 170.0±10.4 | 164.2±7.4 | 0.33 |
| Stroke type (schemic/hemorrhagic) | 8/7 | 7/8 | 7/8 | 0.92 |
| Involved side (Rt/lt) | 9/6 | 8/7 | 10/5 | 0.00* |
Table 3.
Statistical analyses of outcomes of the study in each group.
| Parameter | Group | Pre intervention | Post intervention | Pre-Post difference | Repeated-Measures ANOVA |
|---|---|---|---|---|---|
| NOTE: Values are mean ± standard deviation (SD). VD-SBT: visual deprivation- stable based training; UBT: unstable base training; TUG: Timed Up and Go; 4SS: Four Square Step; FTSS: Five Times Sit to Stand; P*≤0.05 | |||||
| TUG time (sec) | VD-SBT (15) | 16.5±1.8 | 10.0±1.2 | -6.4±2.4 | Time* Group=0.017* |
| UBT (15) | 16.2±2.7 | 15.9±2.3 | -0.7±1.4 | ||
| Control (15) | 16.1±2.6 | 15.4±3 | 0.7±1 | ||
| 4SS time (sec) | VD-SBT (15) | 20.5±2.3 | 12.0±1.2 | -8.5±2.4 | Time* Group= 0.008* |
| UBT (15) | 20.3±2.8 | 18.2±2.7 | -2.8±3.0 | ||
| Control (15) | 20.3±3.0 | 19.6±3.7 | -1.3±0.9 | ||
| FTSS time (sec) | VD-SBT (15) | 18.4±3.6 | 10.9±2.0 | -7.4±3 | Time* Group <0.001* |
| UBT (15) | 21.2±3.0 | 20.1±3.4 | -1.4±1.6 | ||
| Control (15) | 18.8±2.4 | 18.1±2.2 | -0.7±1.6 | ||
The results of two-way Repeated Measures (ANOVA) showed that the main effect of the time is significant, meaning that the mean score of all outcome measures after the intervention is lower than before the intervention in all groups (p <0.001). Also, the main effect of the group was significant for TUG (p= 0.017), 4SS (p=0.008) and FTSS (p<0.001). Multiple comparisons by Tukey HSD method showed that control and unstable groups had a higher mean of all outcome measures than the non-visual group, without significant differences compared to each other in meantime of TUG (0.960), 4SS(0.938) and FTSS (0.215). In addition, the interaction effect was significant (p <0.001), which means that while the meantime of TUG, FFSS and FTSS tests after intervention was slightly lower than before intervention in both control and unstable groups, in the VD-SBT group this decrease was very significant (Fig. 3).
Fig. 3.
Group*Time interaction effect on TUG (a), FSS (b) and FTSS (c). After intervention, VD-SBT group showed a significant decreased in TUG, FSS and FTSS times with respect to UBT and control groups.
Discussion
In our study, we evaluated the effects of the 2 exercise training protocol (visual deprivation- stable based training and unstable based training) on the dynamic and static balance ability of post stroke patients. Despite the fact that the pre-post comparison within each group indicated that balance scores were significantly improved after 4 weeks of intervention, we found that all measures of treated balance by the visual deprivation- stable based training and unstable based training were significantly greater than the control group. Previous studies also indicated that performed training under different sensory conflict conditions in stroke subjects affected their balance ability17,26). The main finding of this study show that after balance training with visual deprivation in stable surface, patients had a significant improvement in their ability to control the static and dynamic balance compared to the unstable base training with open eyes group. It was assumed that the improvement in VD- SB balance training group could be due to the fact that the manipulation of visual input was more effective than the manipulation of standing surface to reweighting sensory information in the field of balance activity. Previous studies found that the exercise training with visual restriction by stroke patient affected their gait dynamic stability27) knee joint proprioception28), balance and concentration ability29), gait velocity and balance7). Results of the present study extended previous results indicating that a training program with visual restrictions could improve the balance ability in persons with stroke more than training at free vision conditions28,30).
Intrinsic and extrinsic feedback could enhance movement performance in healthy subjects. Intrinsic feedback could be mediated by vision, proprioception, touch, pressure and audition31). Extrinsic feedback, which is also known as augmented feedback, supplements an intrinsic feedback and cannot be elaborated without an external source. Both intrinsic and extrinsic feedback controls are affected after stroke31). Impairment in the intrinsic feedback system, especially proprioceptive feedback is common after stroke, and this impairment makes stroke survivors more dependent on an extrinsic feedback system(augmented visual input)and exhibits the excessive dependency on visual input32); hence, this system may be even more important than the intrinsic feedback system. Therefore, patients become unable to use vestibular and proprioceptive input correctly. We hypothesize that, in comparison with free vision conditions, the vestibular and proprioceptive inputs are weighted more heavily in the conditions that extrinsic feedback system is removed (visual deprivation condition).Therefore, we recommended that balance rehabilitation programs after stroke performed under conditions to stimulate the integration of underused sensory input and minimize the overuse of other afferent inputs.
Somewhat surprisingly, the present study found no difference between the training group on the unstable surface and the control group. Most other studies that have examined the training on the unstable surface have reported significance difference between stable and unstable base training11). However, it is worth noting that some studies suggested that older adult used a compensatory strategies of muscle co-contraction33) which is associated with increasing joint stiffness and decreased postural steadiness, when exposed to changes in their base of support34). It is possible that during balance training on unstable surface the patients were using muscle co contraction strategy that made the training ineffective.
The present study had some limitations. First: we used only clinical tests to evaluate the balance ability. Future studies are necessary for further validation of our finding by using quantitative measurements of balance scores. Second: we included male and female patients at later stages after stroke. Further studies should examine roles of sex and chronicity of lesion.
Conclusion
The result of our study suggested that stroke subjects who received balance training in vision restriction conditions could improve the balance more than training at free vision conditions. The reason for this finding may be that the balance training with blocking visual information more facilitated the use of the proprioceptive and vestibular senses. We recommended balance rehabilitation programs after stroke performed under conditions to stimulate the use of underused sensory input to minimize the overuse of other afferent inputs.
Conflict of Interest
There is no conflict of interest to disclose.
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Acknowledgments
We sincerely thank the participants and the Tabas'som stroke rehabilitation staff.
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