Effects of Intensive Whole-Body Vibration Training on Muscle Strength and Balance in Adults With Chronic Stroke: A Randomized Controlled Pilot Study
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Published Online: September 24, 2013
Abstract
Objectives
To investigate the effects of a 6-week whole body vibration (WBV) training program in patients with chronic stroke.
Design
Randomized controlled pilot trial with 6 weeks' follow-up.
Setting
University hospital.
Participants
Adults with chronic stroke (N=15) were randomly assigned to an intervention (n=7) or a control group (n=8).
Interventions
Supervised, intensive WBV training. The vibration group performed a variety of static and dynamic squat exercises on a vibration platform with vibration amplitudes of 1.7 and 2.5mm and frequencies of 35 and 40Hz. The vibration lasted 30 to 60 seconds, with 5 to 17 repetitions per exercise 3 times weekly for 6 weeks. Participants in the control group continued their usual activities and were not involved in any additional training program.
Main Outcome Measures
The primary outcome variable was the isometric and isokinetic muscle strength of the quadriceps (isokinetic dynamometer). Additionally, hamstrings muscle strength, static and dynamic postural control (dynamic posturography), and muscle spasticity (Ashworth Scale) were assessed.
Results
Compliance with the vibration intervention was excellent, and the participants completed all 18 training sessions. Vibration frequencies of both 35 and 40Hz were well tolerated by the patients, and no adverse effects resulting from the vibration were noted. Overall, the effect of intensive WBV intervention resulted in significant between-group differences in favor of the vibration group only in isometric knee extension strength (knee angle, 60°) (P=.022) after 6 weeks of intervention and in isokinetic knee extension strength (velocity, 240°/s) after a 6-week follow-up period (P=.005), both for the paretic leg. Postural control improved after 6 weeks of vibration in the intervention group when the patients had normal vision and a sway-referenced support surface (P<.05). Muscle spasticity was not affected by vibration (P>.05).
Conclusions
These preliminary results suggest that intensive WBV might potentially be a safe and feasible way to increase some aspect of lower limb muscle strength and postural control in adults with chronic stroke. Further studies should focus on evaluating how the training protocol should be administered to achieve the best possible outcome, as well as comparing this training protocol to other interventions.
List of abbreviations:
CON (control), ES (equilibrium score), FAC (functional ambulation classification), SOT (Sensory Organization Test), WBV(whole-body vibration)
Stroke remains the leading cause of adult disability,1 with motor deficits and physical impairments including muscle weakness, loss of mobility, muscle spasticity, and balance problems.2 These impairments may promote a sedentary lifestyle and contribute to secondary complications such as bone loss and fracture risk.3 Muscle weakness results in low muscle forces and thus a deficit of motor control and movement initiations.4 Balance problems increase the risk of falls in older adults with stroke.5 Long-term survivors with stroke also demonstrate long-standing dissatisfaction because of the activity limitation.6
Although functional recovery occurs mostly in the first 3 months after stroke,7 previous research shows that the physical impairments are (partially) reversible with appropriate training. Exercise interventions are now recognized as a useful strategy to improve balance as well as mobility and muscle strength and to enhance functional independence in long-term survivors with stroke.8, 9, 10, 11, 12 Those exercise programs commonly include exercise therapy, neuromuscular electrical stimulation, ergometer training, and training on mechanical devices such as balance trainers.12, 13, 14, 15, 16
Most of these training program have addressed only 1 (or 2) of the impaired domains (eg, either strength or balance). Whole-body vibration (WBV), a recently developed method of neuromuscular training, might be a useful multidimensional approach to counter several of the impairments of patients with stroke. Previous research has shown that WBV training is a useful method to improve muscle strength and postural control in several populations, including sedentary adults17, 18and the elderly.19, 20, 21, 22 These promising findings suggest the possibility that vibration intervention might be a beneficial training therapy for patients with neurologic diseases. However, the effects of WBV training in persons with different neurologic diseases including stroke are limited. Only a few studies23, 24, 25 have evaluated the effect of vibration training on patients with chronic stroke.
One randomized controlled pilot study24 found no effects of 6 weeks' vibration training (amplitude 3.75mm, frequency 25Hz) on muscle strength, muscle tone, and gait performance. The participants performed maximum 12 static knee squats, twice a week.
In another study,23 no effects after 6 weeks (5 days per week, <4min of vibration) of WBV intervention (30Hz, 3mm) were found on functional tests such as the Berg Balance Scale or the Barthel Index. In a study by Lau et al,25 vibration intervention (20–30Hz, .44–.60mm) had no additional effect on neuromotor performance and incidence of falls in adults with chronic stroke compared with control subjects who performed the same exercises but with no vibration. Possible explanations for the different findings in those studies could be that the intensity of the vibration program was too low (e.g. only 4min of vibration per session) or that vibration excitation patterns (amplitude or frequency) could not produce a therapeutic effect, or both. Additionally, the exercises performed on the platform might not have been challenging enough (static exercises).
Therefore, the aim of the current pilot study was to explore the feasibility, safety, and possible benefits of 6 weeks of more intensive WBV training in patients with chronic stroke in comparison to a control (CON) group. Potential effects on knee muscular strength and muscle spasticity were assessed, as well as static and dynamic balance and clinical measures of functional performance, including a standard clinical neurologic examination, Barthel Index, functional ambulation classification (FAC), and a Brunnström-Fugl-Meyer test. Our objective was to obtain preliminary evidence that would allow the design of a larger randomized controlled study.
Methods
Participants and sample size
The study was designed as a randomized controlled pilot trial for patients with chronic stroke who had been admitted to the stroke rehabilitation unit of the University Hospitals Leuven. The inclusion criteria were (1) age between 40 and 75 years; (2) first-ever stroke more than 6 months ago; (3) medically stable; (4) ability to stand independently with or without aids for at least 20 minutes; and (5) ability to perform the experimental treatment independently. Patients were excluded if any of the following were present: acute thrombotic diseases, severe heart and vascular diseases, a pacemaker, an acute hernia, diabetes, tumors, or other neurologic disorders such as Parkinson's disease, multiple sclerosis, epilepsy, peripheral neuropathy, or migraine. Patients who had rheumatoid arthritis, arthrosis, osteoarthritis, diskopathy, or spondylosis were also not allowed to participate in the study.
Ethics
All participants gave written informed consent after receiving both verbal and written information about the study and its possible risks. The study was approved by the Leuven University Human Ethics Committee according to the Declaration of Helsinki.
Recruitment and randomization
Participants were recruited from a physical rehabilitation center in a university hospital. Thirty participants were contacted and underwent medical examination. Seventeen met the inclusion criteria and agreed to participate in the study. Two of the patients refused to continue the study after the first isometric knee muscle strength test before the randomization. In total, 15 participants were included in the study (fig 1).
Fig 1
Flow chart of the participants.
The isometric quadriceps strength in a knee joint angle of 60° of all patients was measured before randomization. Participants were labeled as having “high” or “low” scores based on a cutoff value of 92Nm, and were then randomly assigned to a CON group and a vibration group, using computer-generated random number and concealed allocation.
Intervention
Patients of the intervention group (n=7) participated in a training program on a vertical vibration platform (Power Platea) 3 times a week for 6 weeks, with a minimum rest of 1 day between the training sessions. Patients performed the following exercises: standing on their toes, knee flexion of 50° to 60° (high squat), knee flexion of 90° (deep squat), wide-stance squat, and 1-legged squat. The training program was based on a program designed for the elderly and was previously successfully used.19 Training intensity increased progressively by increasing the frequency (35 and 40Hz) or the amplitude (1.7 and 2.5mm) of the vibration signal, or increasing both. Vibration intensity gradually increased in the first 12 sessions and was more intensive in the last 6 sessions. Training volume rose systematically by increasing the duration of 1 exercise from 30 to 60 seconds, the number of sets of 1 exercise, and/or the number of different exercises. Exercises in symmetric posture as well as weight-bearing exercises to the paretic side were performed. One session had a maximal duration of 30 minutes, and the applied vibration reached 19 minutes in the last weeks of the training program. All patients could walk with or without a walking aid and were capable of standing on the platform. Ankle-foot orthoses (worn by 2 subjects) were taken off during training and measurements. All participants were allowed to have contact with the rails of the platform to support their balance, especially during the dynamic exercises. All training sessions were supervised by a trainer (A.B.) who always stood beside the patients to ensure their safety.
The participants of the CON group were not involved in any additional training program and were asked not to change their lifestyle.
After the training period, there was a follow-up period of 6 weeks. All outcome measurements were performed by an evaluator who was responsible for the instructions to the patients and who was not aware of patients' group allocation. The evaluator was supervised by a senior trainer who was responsible for proper data acquisition and for supervising all training sessions. For practical reasons, it was not possible to have the senior trainer blinded for group allocation, since there was no extra senior evaluator available who was not involved in the training program.
Descriptive measures
A standard clinical neurologic examination assessed for hemianopia, visual and tactile inattention, and aphasia. Both superficial touch and deep sensibility (position, movement, and vibration sense) were evaluated according to the guidelines described by Bickerstaff.26 The Barthel Index determined the patient's degree of independence.27 The FAC was used to evaluate functional (in)dependence of walking and distinguishes 6 levels of walking ability based on the amount of physical support required.28 The Brunnström-Fugl-Meyer test was used to measure sensorimotor impairment. It includes upper and lower extremity sensation, balance, and motor control assessment.28 To evaluate safety, compliance, and feasibility, all patients were encouraged to report possible (adverse) effects and to describe their feelings of perceived exertion during each training session by using Borg's category ratio of perceived exertion scale.29
Outcome measures
All participants were tested at baseline, after the intervention period of 6 weeks, and after 6 weeks' follow-up.
Muscle tone
Muscle spasticity of the gastrocnemius, soleus, quadriceps, hamstrings, adductors, and psoas muscles was measured with the Ashworth Scale.30 The Ashworth Scale ranges between 0 and 4. The full score was the summation of the individual muscle scores, with a maximum of 24 points. The Ashworth Scale has been shown to be a reliable and reproducible method of measuring spasticity.30
Muscle strength
The knee extension and flexion muscle strength tests were performed on both the paretic and nonparetic legs with an isokinetic dynamometer (Biodex Systemb). The maximal voluntary isometric torque (in newton meters) of the quadriceps and hamstrings at a knee angle of 60° was measured. Additionally, isokinetic knee extension-flexion tests against the lever arm of the dynamometer were performed at an angular velocity of 60°/s and 240°/s. All muscle strength measurements were previously shown to be reliable in adults with chronic stroke.24, 31
Postural control
Postural control was evaluated by using a computerized dynamic posturography platform (Equitestc). More specifically, the Sensory Organization Test (SOT) was used to measure the ability to maintain postural control via visual, vestibular, and proprioceptive information, according to a previously described testing protocol.32 SOT analysis provides equilibrium scores (ESs) (%) that reflect how much the subject swayed in the anterior-posterior direction. A mean ES of 3 trials per condition was used for the analysis. High ESs indicated smaller sways, and zero indicated a fall.
Data analysis
Mann-Whitney U tests were used to compare the baseline characteristics of the WBV and CON groups. A Shapiro-Wilk W test was used to assess the distribution for muscle strength, postural control, and muscle tone. Because of the small sample size, differences in muscle strength, postural control, and muscle tone between the WBV and CON groups were tested with nonparametric Mann-Whitney U tests, multiple comparisons. Additionally, Cohen's d effect size was calculated based on means and SD. For Cohen's d, an effect size below 0.3 is considered as a “small” effect, around 0.5 as a “medium” effect, and 0.8 to infinity as a “large” effect. For this pilot study, no correction of the P value for multiple testing was applied because of the exploratory nature of the study. Significance levels for all analyses were set to P<.05. All analyses were executed using the statistical package STATISTICA.d
Results
Participants
Baseline characteristics of the 2 groups are presented in table 1. No differences were observed in the Barthel Index, FAC, and the Brunnström-Fugl-Meyer between the WBV and CON groups before the intervention (P>.05). The maximum score (full independence) on the FAC was achieved in 9 subjects. The results of the FAC showed that 4 patients could walk without the use of a walking aid and were ambulatory-independent only on a level surface. One patient was ambulatory-dependent with supervision without the use of a walking aid and was ambulatory-independent only on a level surface when a walking aid was used. One patient was in a wheelchair but was able to walk ambulatory-dependent with supervision without the use of a walking aid. All other patients could walk ambulatory-independent without a walking aid.
| Characteristics | WBV | CON | Difference (P) |
|---|---|---|---|
| Sex (M/F) | 4/3 (n=7) | 6/2 (n=8) | |
| Age (y) | 57.4±13 | 65.3±3.7 | .13 |
| Type of stroke | |||
| Left/right hemisphere | 4/3 | 4/4 | |
| Ischemic/hemorrhagic lesions | 6/1 | 5/3 | |
| Years after stroke | 7.71±8.6 | 5.28±3.6 | .50 |
| Isometric knee extension strength 60° (Nm) | |||
| Paretic leg | 102.9±15.8 | 90.8±22.4 | .49 |
| Nonparetic leg | 141.1±13.4 | 130.9±17.9 | .24 |
| Descriptive measurements | |||
| Clinical neurologic examination | |||
| Disturbed superficial and deep sensibility | 1 | 3 | |
| Reduced hemianopia | 1 | 2 | |
| Speech problems | 1 | 2 | |
| Barthel Index | 95±7.1 | 86.3±12.2 | .12 |
| Functional ambulation classification | 5 (4–5) | 5 (3–5) | .81 |
| Dependent for supervision | 0 | 2 | |
| Independent, level surface only | 2 | 1 | |
| Independent | 5 | 4 | |
| Brunnström-Fugl-Meyer test | 25±2.9 | 21.1±6.7 | .18 |
NOTE. Values are n, mean ± SD, median (range), or as otherwise indicated.
Abbreviations: F, female; M, male.
One participant in the intervention group refused to repeat the tests after the follow-up. One participant in the CON group did not perform the follow-up tests because of an injury unrelated to the study.
Effect of the intervention
Compliance with the vibration intervention was excellent (100%), and the participants completed all training sessions. All patients tolerated both vibration frequencies of 35Hz and 40Hz, and they did not consider the exercises as too difficult. On average, patients reported a score of 3 on Borg's scale, indicating a moderate degree of exertion. Only 1 person indicated a Borg's score of 6 (heavy). No adverse effects resulting from vibration were reported, although some of the participants described some itching in the legs after the first vibration sessions, but this phenomenon resolved spontaneously. None of the subjects felt any dizziness or fatigue during the vibration training.
Muscle tone
The results of the Ashworth Scale (muscle tone) showed no significant differences between the 2 groups at baseline, after 6 weeks of vibration, and 6 weeks of follow-up (P>.05). The WBV intervention did not affect the level of muscle spasticity (table 2).
| Outcome Measures | Before WBV | After WBV | Follow-up | |||
|---|---|---|---|---|---|---|
| WBV | CON | WBV | CON | WBV | CON | |
| Muscle tone (Ashworth Scale, points) | 4.0 (0–9) | 5.0 (0–14) | 3.0 (0–5) | 5.0 (0–10) | 3.0 (0–9) | 2.0 (0–11) |
| Muscle strength | ||||||
| Isometric knee extension 60° (Nm) | ||||||
| Paretic leg | 102.9±15.8 | 90.8±22.4 | 120.5±9.2∗,‡‡ | 87±23.1 | 114.9±13.3 | 87.2±25.1 |
| Nonparetic leg | 141.1±13.4 | 130.9±17.9 | 156.2±15.3 | 124.2±22.2 | 148±12.6 | 129.1±25.7 |
| Isometric knee flexion 60° (Nm) | ||||||
| Paretic leg | 41.4±15.0 | 30.5±27.2 | 46±16.9 | 36.8±26.6 | 44±16.2 | 35.2±25.7 |
| Nonparetic leg | 83.4±24.5 | 74±25.3 | 81.5±20.5 | 72.4±23.0 | 77.1±18.5 | 71.9±24.5 |
| Isokinetic knee extension 240°/s (Nm) | ||||||
| Paretic leg | 43.1±10.1 | 44.7±12.1 | 50.2±9.3 | 41.4±10.6 | 48.1±7.9∗, ‡‡ | 39.2±9.3† |
| Nonparetic leg | 61.7±8.3 | 59.6±14.2 | 67.3±7.8 | 60.6±11.0 | 67±12.1 | 59.4±13.0 |
| Isokinetic knee flexion 240°/s (Nm) | ||||||
| Paretic leg | 25.3±4.9 | 27.1±13.0 | 28.3±3.4 | 23.7±10.3 | 29.6±6.4 | 24.4±12.3 |
| Nonparetic leg | 52.4±11.8 | 51.7±14.7 | 57.8±10.2 | 54.5±15.6 | 58±11.2 | 49.5±14.6 |
| Isokinetic knee extension 60°/s (Nm) | ||||||
| Paretic leg | 68.7±25.3 | 65.4±16.3 | 82.9±22.2 | 62.5±18.6 | 77.7±21.1 | 63.2±18.0 |
| Nonparetic leg | 111.7±14.6 | 98.1±23.3 | 125±11.7 | 104.3±20.5 | 125.3±14.7 | 110.3±20.0 |
| Isokinetic knee flexion 60°/s (Nm) | ||||||
| Paretic leg | 27.3±13.7 | 20.9±15.3 | 32.5±15 | 24.6±15.7 | 30.3±13.3 | 20.3±12.4 |
| Nonparetic leg | 54.7±14.5 | 53.6±18.0 | 60.6±5.0 | 56.7±17.9 | 64.1±11.5 | 56.1±21.4 |
NOTE. Values are median (minimum–maximum) or mean ± SD.
∗Within-group difference: a significant increase compared with baseline.
†Within-group difference: a significant decrease compared with baseline.
‡Between-group difference: a higher muscle response in WBV group compared with CON group.
Muscle strength
Between-group and within-group differences on muscle strength before and after the intervention and at 6 weeks' follow-up are presented in table 2. No significant differences in knee muscle strength were found between both groups at baseline for both legs (P>.05).
Significant between-group differences were found in favor of the vibration group only in isometric knee extension strength (knee angle, 60°) (P=.022) after 6 weeks of intervention, and in isokinetic knee extension strength (velocity, 240°/s) after the 6-week follow-up period (P=.005), both for the paretic leg. The effect size based on between-group differences is presented in figure 2. The Cohen's d effect size for isometric (knee angle, 60°) and isokinetic (velocity, 60°/s) flexion muscle strength appeared small to medium. The effect size of the intervention for isometric extension strength (knee angle, 60°) was 1.52, and for isokinetic extension muscle strength (velocity, 240°/s) was 1.77.
Fig 2
Effect of the intervention presented as Cohen's d effect size. Effect size is based on between-group differences of the paretic leg. Effect size below 0.3 is considered as a “small” effect, around 0.5 as a “medium” effect, and 0.8 to infinity as a “large” effect. Abbreviations: ISOK, isokinetic muscle strength; ISOM, isometric muscle strength.
No differences between the WBV and CON groups were found for the nonparetic leg. Significant within-group differences were found in the vibration group. Isometric knee extension strength (knee angle, 60°) of the paretic leg increased significantly after the intervention (+18.7%, P=.046) and was maintained after the 6-week follow-up. No changes in isometric knee strength of the paretic leg were found in the CON group (P>.05).
No changes in isokinetic knee muscle strength (velocity, 60°/s) of the paretic leg were found in either the WBV or the CON group after 6-week WBV and 6-week follow-up (P>.05).
No significant change in isokinetic knee extension strength (velocity, 240°/s) of the paretic leg was found after the vibration training (+20.3%, P=.051). At follow-up, the increase did reach significance (+14.1%, P=.046). The isokinetic knee extension strength (velocity, 240°/s) of the paretic leg in the CON group remained the same (−5.17%, P>.05) after the first 6 weeks and decreased significantly after the follow-up (−10.2%, P=.042).
A significant increase in isokinetic knee flexion strength (velocity, 240°/s) of the paretic leg (+13.9%, P<.046) was found in the WBV group after 6 weeks of training. No changes in isokinetic knee flexion strength (velocity, 240°/s) of any of the paretic legs were found in the CON group (P>.05).
No changes in isometric or isokinetic knee strength of the nonparetic leg were found in either the WBV or the CON group (P>.05).
Postural control
Table 3 shows the results on balance in the SOT. Participants in both groups swayed more with increasing difficulty of the test condition (declining ES from C1 to C6 when data from all groups were combined, P<.05). No difference was found between the WBV and CON groups at baseline for any condition. The ES increased significantly after the vibration training only in condition 4—normal vision and sway-referenced support surface (P<.05; effect size, 1.47). The increase was maintained after the follow-up. No significant changes in ES were detected in the CON group (P>.05).
NOTE. SOT equilibrium score (%) presented as mean ± SD for the intervention and CON group at baseline (Pre), after 6 weeks (Post), and after 12 weeks (Follow-up).
Abbreviations: C1, normal vision and normal support surface; C2, eyes closed and normal support surface; C3, sway-referenced vision and normal support surface; C4, normal vision and sway-referenced support surface; C5, eyes closed and sway-referenced support surface; C6, sway-referenced vision and sway-referenced support surface.
∗Within-group difference: a significant increase compared with baseline.
Discussion
The current pilot study suggests that the specific vibration program can have potential beneficial effects on some aspects of knee muscle strength and balance control in patients with chronic stroke. All participants completed the intervention successfully, and compliance was excellent. No adverse effects from vibration were reported, and the increase in training intensity was well tolerated. All participants expressed their willingness to perform different exercises on a vibration platform for even longer periods, suggesting that vibration training may be a feasible training program for patients with chronic stroke.
The main findings of the present randomized controlled pilot study are that patients with chronic stroke improved some aspects of knee muscle strength and postural control after 6 weeks of whole-body intervention. The standardized Cohen'sd effect size (see fig 2) reflected a small to large mean effect as a result of the vibration intervention. This supports the likelihood of a clinically meaningful effect in a larger randomized controlled trial. Although all participants in both groups continued to be involved in their conventional training, knee muscle strength tended to decrease in the CON group, providing further evidence for the additional role of WBV in improving lower limb muscle strength.
Brogårdh et al24 did not find an improvement in isometric or isokinetic knee muscle strength after 6 weeks of WBV. However, we used a different protocol, with patients performing different dynamic exercises (also 1-legged exercise) 3 times weekly for 5.5 to 19 minutes, whereas Brogårdh et al24 only used static squats twice weekly for a maximum of 12 minutes. Also, the vibration parameters (3.75mm, 25Hz) used in their study differed from those in the present study (1.75 and 2.5mm, 35 and 40Hz). In this regard, the muscle loading in Brogårdh's study24 may have been insufficient to result in neuromuscular adaptation. Similarly, a study by Lau et al25 failed to show a difference in isometric knee muscle strength between the vibration group and the CON group after 8 weeks of WBV. A possible reason for this finding is that the participants in the CON group performed the same exercises but without vibration. Moreover, the intensity of the vibration excitation patterns with very low loading (.44–.60mm) used in their study may have been insufficient to induce a tonic vibration reflex and thus, to provoke further training effects in patients with stroke.
In the present study, postural control (ES) did not change significantly when the support surface remained stable (conditions 1–3), most probably because the tests were not challenging enough for the patients. However, postural control improved significantly in the vibration group when the visual information was normal and the support surface was disturbed (condition 4). The improvement in postural control in this condition where ankle proprioception input is disturbed might be related to the improvements in muscle strength and proprioception after vibration training. It should be taken into account that the patients were allowed to have contact with the handrails during the training when they felt unstable, especially while performing dynamic exercises. Therefore, the results should be interpreted with caution, as the effect on postural control could be minimized because the training might not have been challenging enough.
Although some improvements in knee muscle strength and postural control were found, clear recommendations concerning the optimal vibration excitation patterns (amplitude, frequency and duration of the vibration signal) cannot be provided. Therefore, further randomized controlled trials are recommended to provide more insight into how to optimize the vibration protocols for patients with stroke.
Based on the Cohen's d effect size of the isometric knee extension strength of 60°, the effect size of 1.52 (r=.60) was used to calculate the minimum sample size required for a future randomized controlled trial. Based on a 2-tailed alpha level of .05 and a power of 95%, the minimum required total sample size is 40 participants, divided into 2 groups: a vibration group (n=20) and a CON group (n=20).
Study limitations
Our study has several limitations, and the results should be interpreted in the context of its design. First, our sample size was small, and we acknowledge that this was an exploratory pilot study, and the formal sample size was not calculated because of the pilot nature of the study. A larger randomized controlled trial is needed to further investigate the possible positive effects of vibration on patients with stroke. Second, it cannot be excluded that the improvement of knee muscle strength and postural control was the result of the different dynamic exercises performed on the platform. It would have been interesting to include patients in a resistance training group to perform the same exercises on the platform but without vibration (placebo group). Third, the participants and the trainer were not blinded to the group allocation, which was difficult to achieve because of the nature of the study. The trainer supervised all training sessions and all measurements. However, all efforts were made to standardize the measurements to minimize the possible bias. Finally, our preliminary findings should not be generalized to all patients with stroke. Most of the patients in the present study were ambulatory-independent with or without a walking aid and had mild to moderate physical impairments, and thus are not a representative sample of patients with severe impairments after stroke. Moreover, the patients in our study were adults with chronic stroke, and thus the results are not applicable to patients with acute stroke. The possible effect of vibration intervention on patients with severe impairments or patients with acute stroke requires further investigation.
Conclusions
The results of this randomized controlled pilot trial suggest that intensive WBV training may be a safe and feasible training program in patients with chronic stroke. Our preliminary results suggest that some improvements in lower limb muscle strength and postural control occur after 6 weeks of training. Further studies should focus on evaluating how the training protocol should be administered to achieve the best possible outcomes.
Suppliers
- a.Power Plate Acquisitions, LLC, 160 Jan van Gentstraat, 1171GP, Badhoevedorp, The Netherlands.
- b.Biodex Medical Systems Inc, 20 Ramsay Rd, Shirley, NY 11967-4704.
- c.NeuroCom International Inc, 9570 SE Lawnfield Rd, Clackamas, OR 97015.
- d.STATISTICA, version 9; StatSoft Inc, 2300 East 14th St, Tulsa, OK 74104.
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