The goal of this article is to highlight the strengths, limitations, and applications of the method used with whole body vibration on polio survivors with and without post-polio syndrome as a feasible and safe form of weight bearing exercise.
The purpose of the original study was to examine the use of whole body vibration (WBV) on polio survivors with and without post-polio syndrome as a form of weight bearing exercise. The goal of this article is to highlight the strengths, limitations, and applications of the method used. Fifteen participants completed two intervention blocks with a wash-out period in between the blocks. Each block consisted of twice a week (four weeks) WBV interventions, progressing from 10 to 20 min per session. Low intensity (peak to peak displacement 4.53 mm, frequency 24 Hz, g force 2.21) and higher intensity (peak to peak displacement 8.82 mm, frequency 35 Hz, g force 2.76) WBV blocks were used. Pain severity significantly improved in both groups following higher intensity vibration. Walking speed significantly improved in the group who participated in higher intensity intervention first. No study-related adverse events occurred. Even though this population can be at risk of developing overuse-related muscle weakness, fatigue, or pain from excessive physical activity or exercise, the vibration intensity levels utilized did not cause significant muscle weakness, pain, fatigue, or sleep disturbances. Therefore, WBV appears to provide a safe method of weight bearing exercise for this population. Limitations included the lack of measurement of reflexes, muscular activity, or circulation, the difficulty in participant recruitment, and insufficient strength of some participants to stand in recommended position. Strengths included a standard, safe protocol with intentional monitoring of symptoms and the heterogeneity of the participants in their physical abilities. An application of the methods is the home use of WBV to reduce the barriers associated with going to a facility for weight bearing exercise for longer term interventions, and benefits for conditions such as osteoporosis, particularly for aging adults with mobility difficulties due to paralysis or weakness. Presented method may serve as a starting point in future studies.
Whole body vibration (WBV) is reported to give benefits similar to customary exercise in adults, those who are normal or with medical conditions. A vibration platform provides motorized, oscillatory movement to the whole body while the person stands on it. Improvements in pain1,2, strength3,4, balance5,6,7, bone density4,6,8,9, and flexibility5 have been reported. In del Pozo-Cruz et al.'s10 systematic review of WBV studies with people with neurologic conditions, vibration frequencies ranged from 2 to 50 Hz, amplitudes from 0 to 14 mm, 1 to 11 bouts with 1–3 min of rest between bouts, total vibration time per sequence of 0.5 to 15 min, and number of sessions from 1 to 240. WBV acute significant effects were seen in functional balance tests and quadriceps isometric strength in people with multiple sclerosis, postural control and movement items on the Unified Parkinson Disease Rating Scale (UPDRS) in people with Parkinson's disease, and quadriceps isometric and eccentric strength in people post stroke. The only significant change that lasted through the follow-up period was in the UPDRS in people with Parkinson's disease. The reviewers reported that there are few high quality methodological studies available for review and poor consistency of the data between studies10. A pilot study with adults with chronic incomplete spinal cord injury showed significantly faster walking speed and improvement in various gait parameters11. However, a small study with survivors of polio was discontinued due to preliminary data analysis failing to show significant improvement in walking speed and strength12.
Because of the large variations of frequencies and magnitudes used in the WBV intervention studies in the neurologic populations10, the studies reporting the effects of WBV with bone mineral density in post-menopausal women4,6,8,9, older adults6,13,14, and people with fibromyalgia15 were reviewed due to most of the current study's population of survivors of polio being of similar ages, experiencing problems in participating in traditional weight bearing exercises, and having problems with pain and fatigue. In these review studies, 10 to 40 Hz (most in 30 to 35 Hz range) vibration frequencies, with 1-8 mm amplitude, and variable g forces were used4,6,8,9,10,13,14,15. In 2010, Rauch et al.16 published a manuscript describing the need for the standardization and recommendations for reporting WBV studies.
Survivors of polio, with or without post-polio syndrome (PPS), may be challenged in their determination of methods in which to exercise in weight bearing positions to maintain bone density or for other wellness purposes because of their residual weakness or other symptoms of PPS. Exercise has been reported to potentially overly fatigue already overused muscles and worsen symptoms of pain, fatigue, and increased weakness17,18. Few studies with small sample sizes have shown exercise to be safe and beneficial in this population19,20,21,22,23,24.
The goal of the previously conducted study was to examine the use of WBV on polio survivors, with and without PPS, as a possible safe form of weight bearing exercise. Only one prior published study had addressed the use of WBV in people with PPS. The post-polio population has unique issues of chronic muscle weakness or paralysis and joint involvement that impacts their ability to participate in weight bearing exercise; therefore, an exploratory limited-efficacy feasibility study was determined to be necessary25. This article expands upon and demonstrates the method used in the previously published study26. The purpose of this article is to highlight the strengths, limitations, and applications of the method used in that study.
The protocol being described in this article follows the protocol used in the previously published study that abided by the ethical standards for human research of the Internal Review Boards of Texas Woman's University and Baylor College of Medicine in Houston, Texas, USA26.
1. Participant Screening and Study Preparation
2. Experimental Design
3. WBV Interventions
4. Participant Testing
Fifteen of the 21 survivors of polio who consented completed the study, with 14 of those completing the study having PPS. The six people who withdrew did so for nonstudy-related reasons (five work and/or time issues, one medical concern). See Table 2 for demographic characteristics of the participants26.
No significant differences were found between demographic characteristics and pre-intervention outcome measures between the two treatment groups using descriptive statistics and Mann-Whitney U tests. Mann-Whitney U tests were also conducted between the high and low intensity conditions on measures at pretest, posttest, and follow-up for between subject differences. Within subject changes between pretests and posttests were conducted by Wilcoxon signed-rank tests, and Friedman's analysis of variance test was used to study the change over time from pretest through follow-up due to total of five testing sessions to reduce the risk of committing a Type I error with multiple Wilcoxon signed-rank tests. Nonparametric tests were conducted due to the small sample size and lack of normality26,41. Pain severity as measured by the BPI improved significantly after the higher intensity WBV intervention regardless of treatment order (Z = -1.97, p = 0.049, Cohen's d = 0.60), with BPI pain interference trending towards significant improvement (Z = -1.92, p = 0.055, Cohen's d = 0.81). Gait speed significantly improved after the higher intensity intervention, but only for the group that participated in the higher intervention block first, even though both groups experienced both intensities of vibration in intervention blocks (Z = -2.38, p = 0.017, Cohen's d = -1.294). See Table 3 for the data and results for the 10mWT, BPI pain severity, and BPI pain interference. No significant changes occurred in the other outcome measures and following the low intensity protocol, and no changes that occurred were maintained during the two week follow-up period26.
No study-related adverse events occurred. Even though this population can be at risk of developing overuse-related muscle weakness, fatigue, or pain from excessive physical activity or exercise, the vibration intensity levels utilized did not cause significant muscle weakness, pain, fatigue, or sleep disturbances26. The representative results from the prior study need to be interpreted cautiously because of the small study sample size and the huge variability of muscle weakness, pain, walking patterns, and other issues with which survivors of polio present.
Day 1 | Day 2 | Day 3 | Day 4 | Days 5-8 | |
1 WBV on | 1 min | 1.25 min | 1.5 min | 1.75 min | 2 min |
1 Sitting rest off | 1 min | 1 min | 1 min | 1 min | 1 min |
2 WBV on | 1 min | 1.25 min | 1.5 min | 1.75 min | 2 min |
2 Sitting rest off | 1 min | 1 min | 1 min | 1 min | 1 min |
3 WBV on | 1 min | 1.25 min | 1.5 min | 1.75 min | 2 min |
3 Sitting rest off | 1 min | 1 min | 1 min | 1 min | 1 min |
4 WBV on | 1 min | 1.25 min | 1.5 min | 1.75 min | 2 min |
4 Sitting rest off | 1 min | 1 min | 1 min | 1 min | 1 min |
5 WBV on | 1 min | 1.25 min | 1.5 min | 1.75 min | 2 min |
5 Sitting rest off | 1 min | 1 min | 1 min | 1 min | 1 min |
6 WBV on | 1 min | 1.25 min | 1.5 min | 1.75 min | 2 min |
6 Sitting rest off | 1 min | 1 min | 1 min | 1 min | 1 min |
7 WBV on | 1 min | 1.25 min | 1.5 min | 1.75 min | 2 min |
7 Sitting rest off | 1 min | 1 min | 1 min | 1 min | 1 min |
8 WBV on | 1 min | 1.25 min | 1.5 min | 1.75 min | 2 min |
8 Sitting rest off | 1 min | 1 min | 1 min | 1 min | 1 min |
9 WBV on | 1 min | 1.25 min | 1.5 min | 1.75 min | 2 min |
9 Sitting rest off | 1 min | 1 min | 1 min | 1 min | 1 min |
10 WBV on | 1 min | 1.25 min | 1.5 min | 1.75 min | 2 min |
Total time on | 10 min | 12.5 min | 15 min | 17.5 min | 20 min |
Table 1: Scheduled WBV protocol, assuming no adverse events or problems tolerating intervention.
Total Sample | Completing Participants | |
(N=19*) | (N=15) | |
Age (yrs, mean & SD) | 63.53 SD 8.32 | 63.80 SD 9.40 |
Age onset polio (yrs, mean & SD) | 3.55 SD 4.03 | 3.70 SD 4.80 |
PPS diagnosis (yes/no) | 18/1 | 14/1 |
Gender (male/female) | 8/11 | 6/9 |
Race/ethnicity | ||
African American/Black | 2 (1 mixed) | 1 |
Asian/Pacific islander | 1 | 1 |
Hispanic/Latino | 2 | 2 |
Native American | 1 (mixed) | 0 |
White | 13 | 11 |
Walking status | ||
Full-time | 12 | 11 |
Part-time | 6 | 3 |
Not able to walk | 1 | 1 |
Use of orthoses | ||
None | 13 | 9 |
1 or bilateral AFOs | 3 | 3 |
1 or bilateral KAFOs | 2 | 2 |
Not applicable | 1 | 1 |
Use of assistive devices | ||
None | 12 | 8 |
1 or bilateral canes/walking sticks | 5 | 5 |
Bilateral Canadian crutches | 1 | 1 |
Not applicable | 1 | 1 |
Working status | ||
Full-time | 6 | 5 |
Part-time | 4 | 2 |
Retired | 9 | 8 |
* 2 females withdrew from original 21 who consented, prior to data collection. | ||
AFO: Ankle foot orthosis | ||
KAFO: Knee ankle foot orthosis | ||
Table modified and used with permission from original article: Copyright©2018, Taylor & Francis Group, | ||
Physiotherapy Theory and Practice, Da Silva C.P., et al.26 |
Table 2: Demographic characteristics of the participants.
Measure | Lo-Hi Group | Hi-Lo Group | Between Subject Differences p(d) | Within Subject Differences p(dz & eta squared) |
n=6 | n=9 | |||
Mean (Mdn) & SD | Mean (Mdn) & SD | |||
Min-Max | Min-Max | |||
10mWT (m/s) | ||||
Pre-Hi | 1.32(1.07) SD 0.51 | 1.11(1.03) SD 0.39 | 0.346(0.46) | |
0.86-2.11 | 0.69-1.82 | |||
Post-Hi | 1.24(1.09) SD 0.49 | 1.27(1.17) SD 0.47 | 0.698(0.06) | 0.087(0.52) |
0.76-1.96 | 0.82-2.08 | |||
BPI Interference | ||||
Pre-Hi | 3.14(2.50) SD 3.14 | 3.62(3.57) SD 2.50 | 0.796(0.17) | |
0.29-7.57 | 0.00-7.57 | |||
Post-Hi | 2.26(.00) SD 3.09 | 2.39(2.57) SD 2.40 | 0.862(0.05) | 0.055(0.81) |
0.00-5.86 | 0.00-5.14 | |||
BPI Severity | ||||
Pre-Hi | 3.29(2.75) SD 2.57 | 3.44(3.50) SD 1.74 | 0.795(0.07) | |
0.75-7.25 | 0.00-5.50 | |||
Post-Hi | 2.68(0.13) SD 3.63 | 2.61(2.50) SD 2.65 | 0.674(0.02) | 0.049*(0.60) |
0.00-7.25 | 0.00-5.75 | |||
*Significant difference | ||||
Lo-Hi group: low intensity intervention first, higher intensity intervention second | ||||
Hi-Lo group: higher intensity intervention first, low intensity intervention second | ||||
Hi: Higher intensity intervention | ||||
Table modified and used with permission from original article: Copyright©2018, Taylor & Francis Group, | ||||
Physiother Theory Pract, Da Silva C.P., et al.26 |
Table 3: Representative results from outcome measures.
Two different vibration intensities were studied due to the author's clinical experience in working with survivors of polio and hearing their reports of increased muscle weakness, pain, fatigue, and other symptoms of PPS. Little evidence is present in the literature related to safe, effective weight bearing exercise parameters for people with PPS, and only one study12 was published prior to the current study26 with WBV and survivors of polio. To date, only two published articles have studied the use of WBV with polio survivors, and both used the platforms with synchronous vertical oscillations12,26. Therefore, no scientific literature exists related to the use of asynchronous vertical (rotatory) or horizontal vibration in this population.
This author was concerned about possibly worsening their symptoms during the WBV protocols, thereby selecting one intensity fairly typical of that reported in the bone density studies and one much lower, in case the participants would have difficulty tolerating the higher one. The author was vigilant during each vibration session and regularly asked if new symptoms surfaced or typical ones worsened at the beginning of the next session. Group means of RPE after higher intensity sessions were 9.4 to 9.8, or "very light," although the range extended from "no exertion at all" to "extremely hard." Although significant changes only occurred for pain severity across both groups, polio survivors and those who provide care for them may be encouraged that gait endurance, muscle strength, and typical PPS symptoms of fatigue, sleep disturbances, and muscle cramping did not significantly worsen during participation in the protocols. Therefore, a strength of the presented methods includes the use of a standard protocol with intentional monitoring of symptoms by a consistent health care provider knowledgeable about their condition. Because no significant improvements occurred with the low intensity protocol, this intensity or less could possibly be considered for use in a sham intervention in a future randomized controlled study.
Although the knowledge of the effects of WBV with survivors of polio is limited, some critical steps may exist. Due to their typical "type A", hard-working, and eager-to-please personalities, one must ask them specific questions and give them explicit permission to voice concerns or potential problems, such as muscle or joint discomfort, excessive muscular fatigue, or sense of worsened balance, that may arise during the intervention period. Similarly, limiting the WBV total dosage (frequency and intensity)16 per session to no more than 20 min (in one to two min bouts with forced rests) and scheduling sessions with at least one day off in between can help reduce risk of muscle overuse-related fatigue, pain, and cramping17,18.
The mechanisms behind how WBV affects a person's neurophysiological system is poorly understood. The literature has not reported how changes due to WBV in the Hoffman, stretch, and tonic vibratory reflexes of polio survivors who have a depleted alpha motor neuron pool due to initial disease destruction are impacted42,43,44,45,46,47. Reported circulatory changes42, in addition to reports of vibration decreasing delayed-onset muscle soreness after exercise48, may enhance the polio survivors' weaker muscles to work at safe levels for longer time periods during functional activities, such as walking. A limitation of the presented method in this article is that measurement of reflexes, muscular activity, and circulation did not occur.
A second limitation of the method may be that it was tested on such a small group of polio survivors. Recruitment of people to come to a university research lab in the Texas Medical Center twice a week for three months was challenging due to the time, energy, and transportation costs of commuting within a huge metropolitan city. However, a noteworthy amount of participant diversity in physical mobility existed in the 15 individuals who completed the previously reported study26, which could be considered a strength. As seen in Table 2, they ranged from not being able to walk at all, to walking "5%" of total locomotion, to walking full-time, and using no devices at all to utilizing a pair of knee ankle foot orthoses with crutches. All participants except one were able to independently get onto and off the vibration platforms, using the provided handles or grab bar. Even though the participants were able to use their arms for support as needed or preferred, some were unable to shift their weight onto the weaker leg or stand without mechanically locking their knees because of their weakness. Standing with the knees locked could be a potential joint safety issue for some people, and this could be considered a limitation to this method; however, locking also allows more of the vibration g force to extend more cranially27,28. However, this author was surprised by how positively the individuals responded to the vibration during the sessions, with smiles, early arrivals for appointments, requests to "turn it up", and few to no complaints, even with some them dependent on orthoses or assistive devices for safe walking or appearing physically frail. Participants were noted to spontaneously shift weight and change postural alignment, apparently seeking the body position that "felt best" to them. The vibration was truly "whole body" in that it could be heard in their voices while talking during vibration, and dangling earrings or bracelets could be seen or heard to vibrate.
The presented WBV method seems to be a safe, tolerable, and feasible form of weight-bearing exercise for people with weakness or paralysis from polio and PPS. Short lasting improvements in pain and walking speed for some individuals are encouraging for polio survivors who have limited methods to exercise, especially in weight bearing positions. Further research is necessary in order to study long term use and efficacy of WBV in people with PPS and other neurological conditions, particularly to address decreasing barriers to exercise participation and active pursuit of wellness activities. An application of the presented method is the safe use of a WBV platform designed for home use to reduce the barriers of energy, time, and transportation costs associated with going to a health club or therapy clinic. Use within the home can make a longer term intervention feasible, particularly for people with mobility difficulties. Longer intervention studies (at least eight months) will be needed to determine if WBV can significantly impact bone mineral density in female and male polio survivors who have a higher prevalence of osteopenia and osteoporosis than typically aging adults49,50,51,52. Additionally, examining the application of WBV in aging adults with neurologic conditions other than post-polio and its effects on bone mineral density will be important, and the presented methods may serve as a starting point in these studies.
The original study was funded by Post-Polio Health International in 2013, with no cost extension to 2014. Funding for this article was through Texas Woman's University Libraries' Open Access Fund. The results were presented as a poster at the American Physical Therapy Association Combined Sections Meeting, Anaheim, California, US, 2016, and published as a manuscript in Physiotherapy Theory and Practice in 2018 (see reference #26).
The author wishes to acknowledge Elson "Randy" Robertson for his assistance during the filming of the video and participation in the original study. She also wishes to acknowledge the following people for their assistance during the original study: C Lauren Szot, PT, DPT, NCS and Natasha deSa, PT, DPT, NCS as blinded testers and co-authors for original manuscript; Arianne Stoker, PT, DPT, Kelly Hodges, PT, DPT, NCS, Mariana Sanjuan, PT, DPT, and Maggie Strange, PT, DPT for help as DPT students during vibration sessions; and Zoheb Allam, MS and Rene Paulson, PhD for statistical assistance.
Name | Company | Catalog Number | Comments |
WBV Platform | Soloflex, Inc | Used for low intensity WBV intervention | |
Power Plate Pro 5 | Performance Health Systems, LLC | Used for higher intensity WBV intervention | |
Trigno tri-axial accelerometer | Delsys, Inc | Used to measure vibration frequencies and g forces |
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