vision and a sway-referenced support surface (P
Archives of Physical Medicine and Rehabilitation journal homepage: www.archives-pmr.org Archives of Physical Medicine and Rehabilitation 2014;95:439-46
ORIGINAL ARTICLE
Effects of Intensive Whole-Body Vibration Training on Muscle Strength and Balance in Adults With Chronic Stroke: A Randomized Controlled Pilot Study Ekaterina Tankisheva, MD,a An Bogaerts, PhD,b Steven Boonen, MD, PhD,c Hilde Feys, PhD,a Sabine Verschueren, PhDa From the aDepartment of Rehabilitation Science, bDepartment of Kinesiology, and cDivision of Gerontology and Geriatrics, Department of Experimental Medicine, KU LeuveneUniversity of Leuven, Leuven, Belgium.
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 (NZ15) were randomly assigned to an intervention (nZ7) or a control group (nZ8). 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 ) (PZ.022) after 6 weeks of intervention and in isokinetic knee extension strength (velocity, 240 /s) after a 6-week follow-up period (PZ.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). 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. Archives of Physical Medicine and Rehabilitation 2014;95:439-46 ª 2014 by the American Congress of Rehabilitation Medicine
Stroke remains the leading cause of adult disability,1 with motor deficits and physical impairments including muscle weakness, loss
Supported by the Research Foundation Flanders (FWO), Brussels, Belgium (project nos. FWO-G0488-08, FWO-KN-1.5.017.08). No commercial party having a direct financial interest in the results of the research supporting this article has conferred or will confer a benefit on the authors or on any organization with which the authors are associated.
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
0003-9993/14/$36 - see front matter ª 2014 by the American Congress of Rehabilitation Medicine http://dx.doi.org/10.1016/j.apmr.2013.09.009
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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.8-12 Those exercise programs commonly include exercise therapy, neuromuscular electrical stimulation, ergometer training, and training on mechanical devices such as balance trainers.12-16 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 adults17,18 and the elderly.19-22 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 studies23-25 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, .05). The WBV intervention did not affect the level of muscle spasticity (table 2). 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 ) (PZ.022) after 6 weeks of intervention, and in isokinetic knee extension strength (velocity, 240 /s) after the Table 1 Subjects’ characteristics at baseline and differences between groups CON
Difference (P)
Characteristics
WBV
Sex (M/F) Age (y) Type of stroke Left/right hemisphere Ischemic/hemorrhagic lesions Years after stroke Isometric knee extension strength 60 (Nm) Paretic leg Nonparetic leg Descriptive measurements Clinical neurologic examination Disturbed superficial and deep sensibility Reduced hemianopia Speech problems Barthel Index Functional ambulation classification Dependent for supervision Independent, level surface only Independent Brunnstro¨m-Fugl-Meyer test
4/3 (nZ7) 6/2 (nZ8) 57.413 65.33.7 .13 4/3 6/1
4/4 5/3
7.718.6
5.283.6
.50
102.915.8 90.822.4 .49 141.113.4 130.917.9 .24
1
3
1 1 957.1 5 (4e5)
2 2 86.312.2 .12 5 (3e5) .81
0
2
2
1
5 252.9
4 21.16.7
.18
NOTE. Values are n, mean SD, median (range), or as otherwise indicated. Abbreviations: F, female; M, male.
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Whole-body vibration and stroke patients
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6-week follow-up period (PZ.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. 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 (þ18.7%, PZ.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 (þ20.3%, PZ.051). At follow-up, the increase did reach significance (þ14.1%, PZ.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%, PZ.042). A significant increase in isokinetic knee flexion strength (velocity, 240 /s) of the paretic leg (þ13.9%, P.05). No changes in isometric or isokinetic knee strength of the nonparetic leg were found in either the WBVor the CON group (P>.05).
Table 2
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
