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Title: The effect of whole body vibration on physical functioning in older adults
Authors: Lam, Man Hin
Degree: Ph.D.
Issue Date: 2016
Abstract: Background: The proportion of the world's population over the age of 65 years and of older adults living with dementia is increasing exponentially. From a physical perspective, aging is associated with a decline in strength, balance, and mobility that increases the risk for falls and affects the independent living capacity of older adults. As reduced activity levels lead to the deterioration of physical function, early identification and intervention are needed to improve the health and lifespan of older adults. Whole-body vibration therapy (WBV) could be a potentially effective intervention to enhance the benefits of exercise and improve physical function among older adults. As WBV is simple to use, it could be particularly suitable for older adults with cognitive impairments. The overall aim of this thesis was to consolidate existing knowledge regarding the therapeutic effects of WBV training on balance and mobility in older adults, and to provide new insights into the application of WBV training for older adults with dementia. These aims were achieved through a set of six integrated studies. Study 1 (Chapter 2): This systematic review aimed to examine the effect of WBV on balance, mobility and falls among older adults. The databases used included MEDLINE, the Excerpta Medica database, the Cumulative Index to Nursing and Allied Health Literature, the Cochrane Library Databases of Systematic Reviews, Physiotherapy Evidence Database (PEDro), PubMed, and Science Citation Index (last search in October 2011). Randomized controlled trials that investigated the effect of WBV on balance, mobility or falls in older adults were included in this review. The PEDro score was used to examine the methodological quality of the selected studies. The effect of WBV on balance, mobility and fall-related outcomes were extracted. The data extraction and rating were performed by a researcher and the results were confirmed by the principal investigator. Meta-analysis was done if 3 or more studies measured the same outcome of interest. Among 920 articles screened, fifteen articles (thirteen trials) satisfied the criteria and were included in this review. Methodological quality was good for six of the studies (PEDro score=6-7). Meta-analysis revealed that WBV has a significant treatment effect in Tinetti Total Score (p<0.001), Tinetti Body Balance Score (p=0.010) and Timed-Up-and-Go test (p=0.004). No significant improvement was noted in Tinetti Gait Score after WBV training (p=0.120). The effect of WBV on other balance/mobility outcomes and fall rate remains inconclusive. To conclude, WBV may be effective in improving relatively basic balance ability and mobility among older adults, particularly frailer ones. More good-quality WBV trials are required. Study 2 (Chapter 3): This was a systematic review and meta-analysis aimed at reviewing the effect of exercise on physical functioning and quality of life in people with mild cognitive impairment and dementia. Methods and results: An electronic search was conducted using MEDLINE, CINAHL, PubMed, PsycINFO, and The Cochrane Library Databases of Systematic Reviews. The last search was performed on April 25, 2015. Two independent researchers screened and selected randomized controlled trials studying the effect of physical exercise on physical functions and quality of life in individuals with cognitive impairment as the primary diagnosis. Information on participants' characteristics, training protocols, outcomes measures of interest, compliance, and adverse effects were extracted. Metaanalysis was conducted if five similar studies measured comparable outcomes. Thirty seven clinical trials were included. This review revealed strong evidence in support of using supervised physical exercise training to improve strength, mobility, step / stride length, walking speed and quality of life in people with mild cognitive impairment or dementia. Moderate evidence also supported the use of exercise in improving balance, flexibility, endurance, and activities of daily living. The effects on dual-tasking ability, functional performance, and falls remained inconclusive. Less severe cognitive impairment was a determinant of better response to exercise training. To conclude, individuals with cognitive impairments should engage in supervised integrated exercise for about 60 minutes a day and 2-3 days a week to improve physical functioning and quality of life. Study 3 (Chapter 4): Objective: This study aimed to investigate how WBV frequency, amplitude, exercise and their interactions influenced leg muscle activity in elderly adults. Study Design: An experimental study with repeated measures design that involved a group of ambulatory, community-dwelling elderly adults (n=30; 23 women; mean age=61.4±5.3 years). Main outcome measures: Muscle activity of the vastus lateralis (VL), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GS)was measured by surface electromyography (EMG), while participants were performing seven different exercises during 4 WBV conditions (condition 1: frequency= 30Hz, amplitude=0.6mm, intensity=2.25 units of Earth's gravity (g); condition 2: 30Hz, 0.9mm, 3.40g; condition 3: 40Hz, 0.6mm, 3.65g; condition 4: 40Hz, 0.9mm, 5.50g) and a no-WBV condition in a single experimental session. Results: Significantly greatermuscle activity was recorded in VL (3% to 148%), BF (16% to 202%), and GS (19% to 164%) when WBV was added to the exercises, compared with the same exercises without WBV (p≤0.015). The effect of vibration intensity on EMG amplitude was exercise-dependent in VL (p=0.002), and this effect was marginally significant in GS (p=0.052). The EMG activity induced by the four WBV intensities was largely similar, and was the most pronounced during static erect standing and static single leg standing. Conclusions: The EMG amplitude of majority of leg muscles tested was significantly greater during WBV exposure compared with the no-WBV condition. Low-intensity WBV can induce muscle activity as effectively as higher-intensity protocols, and may be the preferred choice for frail elderly adults.
Study 4 (Chapter 5): This was an experimental study aimed at examining the transmission power and purity of vertical (synchronous) whole-body vibrations upon its propagation in the human body among older adults. Methods and results: Forty older adults were tested (33 women; mean age: 60.3±5.7 years). Four vibration frequencies (25, 30, 35, 40 Hz), two amplitudes (0.6 and 0.9 mm), and six different postures were tested (total 48 conditions). Skin-mounted triaxial accelerometers were placed at the medial malleolus, tibial tuberosity, greater trochanter, third lumbar vertebra, and forehead. The transmissibility of vibration was computed as the ratio of the root-mean-square-acceleration at different body sites to that of the platform. Signal purity was expressed by the percentage of total transmitted power within ±1 Hz of the nominal frequency delivered by the platform. It was found that signal transmissibility was dependent upon the interaction between frequency and posture and, to a lesser extent, the interaction between amplitude and posture. Increasing frequency and amplitude was associated with lower transmissibility. Significant resonance was noted at the medial malleolus. Among different postures, tip-toeing led to the lowest transmissibility. Single-leg standing had the highest WBV transmission to the hip, while erect standing had a significantly higher transmissibility to the head than other postures. The purity of the vibration signal was well conserved as the vibrations were transmitted from the feet to the upper body. To conclude, WBV transmissibility is highly influenced by signal frequency, amplitude and posture. These parameters should be carefully considered when prescribing WBV to older adults. Study 5 (Chapter 6): This was a randomized controlled trial that aimed to investigate the therapeutic effects of whole body vibration (WBV) on enhancing the outcomes of a comprehensive exercise training program to improve physical function among institutionalized older adults. Methods and results: Seventy-three institutionalized older adults were randomly allocated to one of three training groups: group 1, a comprehensive strength and balance training program combined with WBV; group 2, a comprehensive strength and balance training program without WBV; and group 3, social and recreational activities consisting of upper limb exercises only. All participants completed 3 training sessions per week for 8 weeks. Measured outcomes included assessment of mobility, balance, lower limb strength, walking endurance, and self-reported balance confidence. Outcomes were measured pre- and post-intervention. Participants were also followed up for 1 year after the end of the training session to record the incidence of falls that required medical attention. Two-way repeated measures analysis of variance was used to evaluate the post-intervention change of measured variables, from baseline, between-groups. The intent-to-treat analysis identified a significant time × group interaction for lower limb strength, evaluated using the time to complete 5 repetitions of sit-to-stand (p=0.048). Post-hoc analysis identified the interaction effect to be contributed by the improvement in lower limb strength for the exercise group without WBV, compared to a decline in strength in the control group (p=0.030). No significant time × group interaction was identified for other outcomes (p≥0.065). To conclude, adding WBV did not enhance the effect of a comprehensive exercise program on the physical function of institutionalized older adults. Although our exercise program was effective in improving lower limb strength, there were no therapeutic effects on balance and mobility. A longer program duration and more challenging balance activities may be needed to improve balance and mobility in these individuals. Study 6 (Chapter 7): This was a randomized controlled trial aimed at evaluating the feasibility, safety, and therapeutic effectiveness of WBV in improving lower limb strength, balance, and mobility among individuals with mild or moderate dementia. Methods and results: Fifty-four older adults (40 women; mean (SD) age: 79.8 (6.1) years) with mild or moderate dementia were recruited from two day-care centers. They were randomly allocated to either the WBV training group (intervention group) or usual care in the daycare center (control group). The intervention period lasted for nine weeks (18 sessions). All subjects were assessed pre- and post-intervention, and three months after the intervention ended. The primary outcome was functional mobility, measured using the Timed Up-and-Go (TUG) test. The following secondary outcomes were evaluated: balance, using the Berg Balance Scale; lower limb strength, using the time to complete 5 repetitions of sit-to-stand; quality of life, using the Quality of Life in Alzheimer's disease questionnaire; and balance confidence, using the Activities specific Balance Confidence scale. The feasibility and safety of the WBV intervention were evaluated in terms of attendance rate, the incidence of adverse events, and feedback provided by trainers. The attendance rate for the training was high (86.0%) with a very low incidence of adverse events: 2 of the 27 participants reported mild knee pain. WBV did not provide additional benefits compared to usual care for the primary outcome and for all secondary outcomes assessed. To conclude, WBV training is feasible and safe to use with people with mild or moderate dementia. However, nine weeks (18 sessions) of vertical WBV (30 Hz, 2 mm peak-to-peak amplitude) did not yield further improvement in physical function and quality of life than a usual activity program, provided at a daycare center, among community-dwelling older adults with dementia. Conclusion: The transmission of WBV through the human body is complex and will be highly influenced by the intensity of WBV and by exercise postures used for training. Although WBV does augment activation of lower limb muscles during exercise, our two randomized controlled trials did not provide evidence of the effectiveness of WBV in improving physical function among institutionalized older adults or among community-dwelling older adults with mild or moderate dementia.
Subjects: Exercise for older people.
Vibration -- Therapeutic use.
Hong Kong Polytechnic University -- Dissertations
Pages: xxxi, 395 pages
Appears in Collections:Thesis

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