- Email: [email protected]
An exploratory study of vibration therapy on muscle function in patients with peripheral artery disease
An exploratory study of vibration therapy on muscle function in patients with peripheral artery disease Darryl J. Cochrane, PhD,a Fiona Cochrane, BN,b and Justin A. Roake, PhD,b,c Palmerston North and Christchurch, New Zealand
ABSTRACT Objective: The purpose of this exploratory study was to determine whether a single session of vibration therapy (VT) would improve muscular and functional performance in individuals with symptomatic peripheral artery disease (PAD). Methods: In a randomized, balanced cross-over design fourteen PAD participants with intermittent claudication (mean 6 standard deviation; age, 73.9 6 4.6 years; height, 172.6 6 68.4 cm; body mass, 85.2 6 15.7 kg) performed VT and control that involved repeated chair rises, timed up-and-go test, and 6-minute walk test. Each intervention was separated by at least 2 days. Wearable VT devices were positioned on the right and left lower limbs that were turned on during functional testing but were turned off for the control intervention. Results: VT significantly improved (P < .05) repeated chair rises and timed up-and-go test compared with control with a small effect size of 0.46 and 0.45, respectively. Similarly, a significant (P < .01) and meaningful change in 6-minute walk test was noted in VT compared with control. Conclusions: This exploratory study suggest that VT may enhance functional strength, mobility, and walking performance by extending the onset of claudication and increasing walking distance in PAD with intermittent claudication. However, further study is required to confirm and extend these preliminary findings and determine the potential mechanisms of action in VT. (J Vasc Surg 2019;-:1-6.) Keywords: Vibration therapy; Intermittent claudication; Stand-to-sit; Timed get-up-and-go; 6-minute walk; Mobility
Peripheral artery disease (PAD) is highly prevalent, costly, and deadly condition that affects 15% to 20% of individuals over 70 years of age.1 The global prevalence of PAD has increased by 23.5% from 2000 to 2010,1 resulting in an increased risk of cardiovascular mortality.2 PAD may be asymptomatic but many people with PAD suffer from limb disability and intermittent claudication (IC), which is characterized by leg pain when walking that is relieved rapidly by resting. Other adverse changes associated with PAD lower limb function include reduced leg strength, impaired balance, slow walking speed, functional decline, and mobility loss.2
From the School of Sport, Exercise and Nutrition, Massey Universitya; and the Department of Vascular, Endovascular and Transplant Surgery, Christchurch Hospital,b and the Department of Surgery, University of Otago, Christchurch.c Funded by Palmerston North Medical Research Foundation. The Foundation has no involvement in the study design; collection, analysis and interpretation; manuscript writing; or the decision to submit the manuscript for publication. Author conflict of interest: none. Correspondence: Darryl J. Cochrane, PhD, School of Sport, Exercise & Nutrition, Massey University, Private Bag 11 222, Palmerston North, New Zealand (e-mail: [email protected]). The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest. 0741-5214 Copyright Ó 2019 by the Society for Vascular Surgery. Published by Elsevier Inc. https://doi.org/10.1016/j.jvs.2019.06.214
Exercise rehabilitation is central to treating IC with revascularization reserved for those who have been unsuccessful with exercise training or have a favorable risk-benefit ratio. Exercise is regarded as a safe and effective treatment for IC where treadmill exercise has reported improved quality of life3 and increased maximal walking distance by 50% to 100%.4 Exercise is seen as an effective noninterventional approach to reducing leg symptoms that are best achieved from supervised exercise programmes.5 Despite this, there is still a lack of specific information about how PAD patients with IC should undertake exercise training.6 Although walking is a common modality to treat IC, the ischemic pain induced by walking may generate frustration and discourage motivation to participate in exercise. This may further reduce physical activity levels through a decline in exercise adherence that results in subsequent functional disability7 and increases the risk of comorbidities associated with IC.8 If an alternative exercise to walking was able to improve functional performance and reduce mobility loss, it would be a welcome addition for symptomatic PAD, especially if the intervention was able to reduce pain and leg symptoms when performing walking and functional activities. One such modality that may assist with this goal is vibration therapy (VT), and we postulate that it may assist people suffering from IC. Acute vibration exposure increases muscle activation,9 blood flow,10 and oxygen uptake,11 which are potentially important in alleviating PAD
1
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symptoms and in multiple sclerosis patients a single vibration session reported improved balance, mobility, and walking.12 Wearable vibration is an emerging technology that has evolved from local vibration, which has relied on hand-held, cabled-powered vibratory; however, wearable vibration allows for greater portability that can be applied to the target muscle with ease. Recently, wearable vibration for 10 minutes (120 Hz) significantly enhanced muscular power in master athletes13 and 15 minutes (120 Hz) of vibration attenuated muscle soreness and improved range of motion after strenuous eccentric exercise of the elbow flexors.14 Thus, a single dose of vibration has scientific merit for therapeutic benefit but currently there is a lack of research to determine the efficacy of VT; therefore, based on the aforementioned scientific evidence, the purpose of this current study was to determine whether a single session of VT may benefit muscular performance in PAD individuals that have IC. It was hypothesized that VT would improve walking performance and functional mobility.
METHODS Study design In a randomized, balanced cross-over design all participants performed vibration therapy (VT) and control (no VT) interventions with at least 2 days separating each intervention, which is sufficient recovery as the benefits of a single session of vibration declines in an hour.15 Every participant completed the following testing order of repeated chair rises (RCR; 2), timed up-and-go test (2), and 6-minute walk test (6-MWT). Between repetitions, 60 and 30 seconds of rest was enforced for RCR and timed up-and-go test, respectively. For VT, the device was turned on at the commencement of the RCR and switched off at the termination of the 6-MWT. For controls, the VT device was placed in the exact position as VT, but it was not turned on during testing. The time to complete VT and control interventions were also recorded. Participants were asked to abstain from alcohol, caffeine, and exercise for 24 hours before testing. To account for daily biorhythms, all testing was conducted at the same time of day and participants were encouraged to maintain their dietary and sleeping habits during the study. Participants Fourteen participants with PAD and IC (femoropopliteal lesion) were previously assessed by a specialist using noninvasive techniques such as magnetic resonance imaging and computed tomography angiography. Participants volunteering for the study had to meet the following criteria: a history of walking leg pain, resting ankle brachial index of less than 0.9, and ambulatory leg pain confirmed by walking exercise. Exclusion criteria included an inability to walk without a walker or
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ARTICLE HIGHLIGHTS d
d
d
Type of Research: Single-center randomized crossover study Key Findings: A single session of vibration therapy improved functional strength (12%), mobility (12%), and walking performance by extending the onset of claudication (63%) and increasing walking distance (13%) in 14 patients with peripheral artery disease and intermittent claudication. Take Home Message: Acute vibration therapy has shown promising results to assisting patients with intermittent claudication in alleviating exertional leg symptoms while performing conventional walking exercise.
wheelchair, severe functional limitation, terminal illness, and recent major operation.16 Further demographic data are included in Table I. Written informed consent was obtained from participants, and ethical approval was granted by the university’s human ethics committee. The sample size of this study was calculated from the primary outcome of 6-MWT. Previous research has indicated that a mean change for between-group comparison of 50 m represents a substantial meaningful difference in the 6-MWT.17 From this, the current study was designed to have 80% power to detect a change of 55 m. Using a paired t test (2-sided, a ¼ .05) with a standard deviation of 65 m, a sample size of 14 participants was required. Measures RCR. Rising to stand from a seated position is a very common task in daily life where, RCR assesses lower limb functional strength18 and is a valid measure of dynamic balance and functional mobility.19 RCR is strongly correlated with the 6-MWT20 and has excellent relative and absolute reliability in older adults.19 Seated in a straight-backed chair (seat height of 42 cm), participants were asked to fold their arms across their chest and ascend to an upright stance before sitting down five consecutive times as quickly as possible. Time was recorded from rising of the first repetition and terminated when returning to a seated position of the fifth repetition. This test was repeated after 60 seconds of rest and the mean of the two attempts were used for analysis. Timed up-and-go test. The timed up-and-go test (TUG) assesses functional mobility21 and has good reliability and validity.22 From a standardized chair (seat height of 42 cm) with each hand placed on the respective thigh, participants ascended and walked 3 m to a cone placed in front of the chair, turned and walked back to the chair to resume a seated position as quickly as possible. Time was recorded from the initial movement to the return of
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Table I. Participant characteristics Age, years No. of participants
73.9 6 4.6 14
Sex Male
86
Female
14
Height, cm
172.6 6 8.4
Weight, kg
85.2 6 15.7
Body mass index
28.7 6 5.5
Resting ABI
0.74 6 20
Unilateral symptoms
29
Bilateral symptoms
71
Current smoker
7
Diabetes mellitus
7
Beta-blocker Antihypertensive agent
7 57
Statin
42
Antiplatelet agenta
64
ABI, Ankle-brachial index. Values are presented as mean 6 standard deviation or percentages. a Aspirin.
the seated position. The test was repeated after 60 seconds of rest and the mean of the two attempts were used for analysis. After the TUG, a 30-second rest was enforced before the 6-MWT. 6-MWT. The self-paced 6-MWT assesses the submaximal level of functional capacity that reflects activities of daily living that are performed at submaximal levels of exertion.23 The 6-MWT is regarded a reliable measure of functional exercise capacity in persons with PAD.24 Following standardized procedures,23 participants were instructed to walk back and forth along a 30-m corridor for 6 minutes continuously with the aim of walking as many laps (covering as much ground) as possible within 6 minutes. Participants were permitted to rest if necessary but were encouraged to continue walking once the claudication pain subsided sufficiently.25 The claudication pain onset time (COT) and claudication pain onset distance (COD) were noted along with the total distance (TD) covered in 6 minutes. Methodology VT. To ensure the greatest vibration response in generating a systemic effect a wearable vibratory device (MyoVolt, Christchurch, New Zealand) was positioned on the lateral, medial gastrocnemius and the intersection of these two muscles of the right and left limb and were held in place by an elastic stocking (Fig). Using the continuous mode the vibration devices were turned on at the commencement of RCR and turned off at the termination of 6-MWT and the exposure time of VT was recorded. When fully charged the Myovolt device can last up to approximately
80 minutes. Each treatment cycle is 10 minutes, when the device automatically switches off; if another cycle is required, the switch can be turned on to reactivate the device. Currently, there is scant research for VT prescription (duration, vibration frequency, and vibration amplitude). However, applying the Myovolt for 10 and 15 minutes at a vibration frequency of 120 Hz has been shown to enhance muscular power in master athletes13 and accelerate muscle recovery after strenuous exercise in physically active males,14 respectively. From these findings, the selection of 120 Hz with an amplitude of 1.2 mm was considered sufficient to elicit the appropriate changes. Controls. For the control condition, the wearable vibratory devices were positioned in the exact position as VT, but were not switched on. The time was also noted from the commencement of RCR to the termination of 6-MWT that allowed a direct comparison with VT time. Statistical analysis All statistical analysis was computed by using Statistical Package for Social Sciences (SPSS, version 23, IBM, Armonk, NY) and all values are presented as mean 6 standard deviation. The level of significance was set at a P value of .05 or less. All data were normally distributed according to Kolmogorov-Smirnov test and sphericity was not violated. Dependent variables (RCR, TUG, COT, COD, and TD) were evaluated with a repeated measure analysis of variance. Where significant F values were achieved, pairwise comparisons were performed using the Bonferroni post hoc procedure. Effect size (mean change/pooled standard deviation) were calculated to quantify the magnitude of the vibration effect on RCR, TUG, COT, COD, and TD. Effect sizes were classified using the following criteria: 0.0, trivial; 0.2, small; 0.6, moderate; 1.2, large; and 2.0, very large.26
RESULTS VT significantly (P < .05) improved RCR and TUG by approximately 12%, with a small effect size of 0.46 and 0.45, respectively (Table II) compared with control. For the 6-MWT, VT significantly (P < .01) enhanced COT (65 seconds), COD (79 m), and TD (48 m) that revealed large (1.25), moderate (1.07), and small (0.33) effect sizes, respectively (Table II) compared with controls. The duration of VT exposure was 9:56 6 0:45 minutes, which was statistically similar (P > .05) to the control duration (9:47 6 0:57 minutes).
DISCUSSION To our knowledge, this is the first study to examine if a single session of VT can improve functional performance and walk time of patients with PAD with IC. These results confirm the hypothesis that VT significantly improved RCR, TUG, and 6-MWT, compared with control. The beneficial effects of exercise in PAD have been well-documented; however, the mechanisms remain
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Fig. Positioning of VT (A) of the right gastrocnemius held in place with an elastic stocking (B).
uncertain.27 Exercise has the ability to improve vascular and skeletal muscle function in PAD.28 Similarly, VT has been reported to increase tissue oxygenation and perfusion in healthy males, making it a viable therapeutic option for PAD to reduce the risk of short-term ischaemia and reperfusion-induced cell damage.29 To date, research has focused on whole-body vibration (WBV) therapy in various populations.30 Given the emergence of wearable vibration as a novel therapy, it could theoretically improve endothelial and neuromuscular function and decrease systemic inflammation. Owing to the scope of the study, these measures were not assessed directly. However, the present findings indicate that RCR and TUG elicited a small meaningful change of 14% and 13%, respectively. This finding is in agreement with earlier WBV studies performed on children with cerebral palsy,31 in multiple sclerosis,32 and for patients with chronic stroke.33 RCR and TUG are measures of lower limb muscle strength and balance21 that are influenced by vibration. Single session WBV studies have revealed increases in muscle strength15 and balance,12,34 although others have failed to show any improvement.35 It has
been suggested that strength and balance improvements are a result of vibration eliciting a neuromuscular response, thereby increasing muscle activity and motor unit recruitment.15,34 The direct application of vibration on muscle is capable of increasing Ia afferent discharge that elicits an excitatory response of the alpha motorneurons,36 which may explain the transient increase in muscle strength.37 This finding has been supported by previous research that reported an enhancement in muscle power following a single session of VT,13 and it plausible that the current wearable VT device was able to exert similar physiologic changes to improve RCR and TUF. Similarly, direct vibration has the capacity to influence other body receptors that are likely to improve balance.12 It is unclear of how long the beneficial effects last after a bout of vibration, but WBV research from young healthy adults reported a transient (after 2 minutes) improvement in lower limb muscle performance that returned to baseline at 60 minutes.15 Similarly, in stroke patients, knee extension strength and muscle activity increased 5 to 10 minutes after a single session of WBV.38 Therefore,
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Table II. Control and vibration therapy (VT) 6-MWT RCR, seconds
TUG, seconds
COT, seconds
COD, meters
TD, meters
Control
14.23 6 4.04
8.69 6 2.08
102 6 36
125.14 6 50.94
358.43 6 142.36
VT
12.49 6 3.48a
7.67 6 2.45a
167 6 63b
204.29 6 91.16b
406.29 6 143.66b
Change
1.74 6 2.63
1.02 6 1.34
65 6 32
79.14 6 50.89
47.86 6 24.06
0.46
0.45
1.25
1.07
0.33
(VT-Control) ES
6-MWT, 6-minute walk test; COD, claudication pain onset distance; COT, claudication pain onset time; ES, effect size; RCR, repeated chair rises; TD, total distance; TUG, timed up-and-go. Values are presented as mean 6 standard deviation. a P < .05 compared with control. b P < .01 compared with control.
it is plausible that patients with IC would not have to wear the VT device while walking; it could be passively administered and over a longer period of exposure it may provide gradual and sustained improvement. Evidence to support this finding indicates that long-term vibration training (3 wk1 for 8 weeks) in older people improved muscle strength, gait, and TUG compared with a control group, and was comparable with changes recorded from the exercise group.39 The current results illustrate VT produced a large meaningful improvement in COT and COD, whereas a small meaningful change was recorded for TD during 6-MWT. A possible explanation for the current improvement in 6-MWT may be in part due to the potentiation of neuromuscular properties of neurogenic excitability40 and/or muscle tuning.41 This acute change would translate to assisting the control and execution of walking performance. Other factors, such as increased blood flow and muscle tissue oxygenation may also contribute to enhancing 6-MWT. A single session of localized vibration applied to the plantar area of the foot has been shown to calf blood flow.42 Equally, muscle tissue oxygenation is increased during a single session of WBV.29 Consequently, the current VT may have elevated blood flow and tissue oxygenation resulting greater muscle perfusion that would assist walking performance; however, this finding requires further research to substantiate this claim. Finally, applying vibration has been shown to decrease acute musculoskeletal pain43 and reduce pain caused by muscle pressure.44 Therefore, VT may have the capacity to decrease or mask the perception of pain while performing the 6-MWT.
CONCLUSIONS A single session of wearable VT significantly improved functional performance measures of RCR, TUG, and 6MWT. The clinical significance of the small and large meaningful changes suggests that VT may acutely assist PAD patients with IC. Given the ease of use and portability of VT it may improve exercise tolerance by improving functional strength, mobility and extending the onset of claudication and increase walking distance;
however, a randomized clinical training study is required to fully understand the efficacy of VT by comparing it to traditional exercise, such as walking. We are grateful to the participants who gave their time and to the Department of Physiotherapy, Christchurch Hospital for the use of their facilities and Palmerston North Medical Research Foundation for funding this study.
AUTHOR CONTRIBUTIONS Conception and design: DC, JR Analysis and interpretation: DC, JR Data collection: DC, FC Writing the article: DC Critical revision of the article: DC, FC, JR Final approval of the article: DC, FC, JR Statistical analysis: DC Obtained funding: DC Overall responsibility: DC
REFERENCES 1. Fowkes FGR, Rudan D, Rudan I, Aboyans V, Denenberg JO, McDermott MM, et al. Comparison of global estimates of prevalence and risk factors for peripheral artery disease in 2000 and 2010: a systematic review and analysis. Lancet 2013;382:1329-40. 2. McDermott MM, Greenland P, Liu K, Guralnik JM, Criqui MH, Dolan NC, et al. Leg symptoms in peripheral arterial disease associated clinical characteristics and functional impairment. JAMA 2001;286:1599-606. 3. Kruidenier LM, Viechtbauer W, Nicolai SP, Buller H, Prins MH, Teijink JAW. Treatment for intermittent claudication and the effects on walking distance and quality of life. Vascular 2012;20:20-35. 4. Fakhry F, van de Luijtgaarden KM, Bax L, den Hoed PT, Hunink MGM, Rouwet EV, et al. Supervised walking therapy in patients with intermittent claudication. J Vasc Surg 2012;56:1132-42. 5. Fokkenrood HJP, Bendermacher BLW, Lauret GJ, Willigendael EM, Prins MH, Teijink JAW. Supervised exercise therapy versus non-supervised exercise therapy for intermittent claudication. Cochrane Database Syst Rev 2013;(8): CD005263.
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6. Parmenter BJ, Dieberg G, Phipps G, Smart NA. Exercise training for health-related quality of life in peripheral artery disease: a systematic review and meta-analysis. Vasc Med 2015;20:30-40. 7. McDermott MM, Greenland P, Ferrucci L, Criqui MH, Liu K, Sharma L, et al. Lower extremity performance is associated with daily life physical activity in individuals with and without peripheral arterial disease. J Am Geriatr Soc 2002;50:247-55. 8. Otis RB, Brown AS, Womack CJ, Fonong T, Gardner AW. Relationship between physical activity recall and free-living daily physical activity in older claudicants. Angiology 2000;51:181-8. 9. Pollock RD, Woledge RC, Mills KR, Martin FC, Newham DJ. Muscle activity and acceleration during whole body vibration: effect of frequency and amplitude. Clin Biomech 2010;25:840-6. 10. Kerschan-Schindl K, Grampp S, Henk C, Resch H, Preisinger E, Fialka-Moser V, et al. Whole-body vibration exercise leads to alterations in muscle blood volume. Clin Physiol 2001;21:377-82. 11. Rittweger J, Schiessl H, Felsenberg D. Oxygen uptake during whole-body vibration exercise: comparison with squatting as a slow voluntary movement. Eur J Appl Physiol 2001;86: 169-73. 12. Schuhfried O, Mittermaier C, Jovanovic T, Pieber K, Paternostro-Sluga T. Effects of whole-body vibration in patients with multiple sclerosis: a pilot study. Clin Rehabil 2005;19:834-42. 13. Cochrane DJ. The acute effect of direct vibration on muscular power performance in master athletes. Int J Sports Med 2016;37:144-8. 14. Cochrane DJ. Effectiveness of using wearable vibration therapy to alleviate muscle soreness. Eur J Appl Physiol 2017;117:501-9. 15. Torvinen S, Kannus P, Sievanen H, Jarvinen TAH, Pasanen M, Kontulainen S, et al. Effect of a vibration exposure on muscular performance and body balance. Randomized cross-over study. Clin Physiol Funct Imaging 2002;22:145-52. 16. White SH, McDermott MM, Sufit RL, Kosmac K, Bugg AW, Gonzalez-Freire M, et al. Walking performance is positively correlated to calf muscle fiber size in peripheral artery disease subjects, but fibers show aberrant mitophagy: an observational study. J Transl Med 2016;14:284. 17. Perera S, Mody SH, Woodman RC, Studenski SA. Meaningful change and responsiveness in common physical performance measures in older adults. J Am Geriatr Soc 2006;54: 743-9. 18. Csuka M, McCarty DJ. Simple method for measurement of lower-extremity muscle strength. Am J Med 1985;78:77-81. 19. Goldberg A, Chavis M, Watkins J, Wilson T. The five-times-sitto-stand test: validity, reliability and detectable change in older females. Aging Clin Exp Res 2012;24:339-44. 20. Ozatevli S, Ozden A, Itil O, Akkoclu A. Comparison of the sitto-stand test with 6 min walk test in patients with chronic obstructive pulmonary disease. Respir Med 2007;101:286-93. 21. Podsiadlo D, Richardson S. The timed up and go - a test of basic functional mobility for frail elderly persons. J Am Geriatr Soc 1991;39:142-8. 22. Morris S, Morris ME, Iansek R. Reliability of measurements obtained with the Timed "Up & Go" Test in people with Parkinson disease. Phys Ther 2001;81:810-8. 23. Crapo RO, Casaburi R, Coates AL, Enright PL, MacIntyre NR, McKay RT, et al. ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med 2002;166:111-7. 24. Montgomery PS, Gardner AW. The clinical utility of a sixminute walk test in peripheral arterial occlusive disease patients. J Am Geriatr Soc 1998;46:706-11.
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25. McGuigan MRM, Bronks R, Newton RU, Graham JC, Cody DV. Exercise performance, functional status, and hemodynamic assessment of elderly patients with intermittent claudication. J Aging Phys Act 2002;10:28-40. 26. Hopkins WG. A scale of magnitudes for effect statistics: a new view of statistics. 2006. Available at: http://sportsci.org/ resource/stats/effectmag.html. Accessed January 17, 2019. 27. Hamburg NM, Balady GJ. Exercise rehabilitation in peripheral artery disease functional impact and mechanisms of benefits. Circulation 2011;123:87-97. 28. Hamburg NM, Creager MA. Pathophysiology of intermittent claudication in peripheral artery disease. Circ J 2017;81:281-9. 29. Rittweger J, Moss AD, Colier W, Stewart C, Degens H. Muscle tissue oxygenation and VEGF in VO2-matched vibration and squatting exercise. Clin Physiol Funct Imaging 2010;30: 269-78. 30. Cochrane DJ. Vibration exercise: the potential benefits. Int J Sports Med 2011;32:75-99. 31. Tupimai T, Peungsuwan P, Prasertnoo J, Yamauchi J. Effect of combining passive muscle stretching and whole body vibration on spasticity and physical performance of children and adolescents with cerebral palsy. J Phys Ther Sci 2016;28:7-13. 32. Hilgers C, Mundermann A, Riehle H, Dettmers C. Effects of whole-body vibration training on physical function in patients with Multiple Sclerosis. NeuroRehabilitation 2013;32: 655-63. 33. Khalifeloo M, Naghdi S, Ansari NN, Akbari M, Jalaie S, Jannat D, et al. A study on the immediate effects of plantar vibration on balance dysfunction in patients with stroke. J Exerc Rehabil 2018;14:259-66. 34. Turbanski S, Haas CT, Schmidtbleicher D, Friedrich A, Duisberg P. Effects of random whole-body vibration on postural control in Parkinson’s disease. Res Sports Med 2005;13:243-56. 35. Humphries B, Warman G, Purton J, Doyle T, Dugan E. The influence of vibration on muscle activation and rate of force development during maximal isometric contractions. J Sports Sci Med 2004;3:16-22. 36. Eklund G, Hagbarth KE. Normal variability of tonic vibration reflexes in man. Exp Neurol 1966;16:80-92. 37. Warman G, Humphries B, Purton J. The effects of timing and application of vibration on muscular contractions. Aviat Space Environ Med 2002;73:119-27. 38. Tihanyi TK, Horvath M, Fazekas G, Hortobagyi T, Tihanyi J. One session of whole body vibration increases voluntary muscle strength transiently in patients with stroke. Clin Rehabil 2007;21:782-93. 39. Rees S, Murphy A, Watsford M. Effects of vibration exercise on muscle performance and mobility in an older population. J Aging Phys Act 2007;15:367-81. 40. Griffin L, Garland SJ, Ivanova T, Gossen ER. Muscle vibration sustains motor unit firing rate during submaximal isometric fatigue in humans. J Physiol 2001;535:929-36. 41. Wakeling JM, Nigg BM, Rozitis AI. Muscle activity damps the soft tissue resonance that occurs in response to pulsed and continuous vibrations. J Appl Physiol 2002;93:1093-103. 42. Stewart JM, Karman C, Montgomery LD, McLeod KJ. Plantar vibration improves leg fluid flow in perimenopausal women. Am J Regul Integr Comp Physiol 2005;288:R623-9. 43. Lundeberg T, Nordemar R, Ottoson D. Pain alleviation by vibratory stimulation. Pain 1984;20:25-44. 44. Weerakkody NS, Whitehead NR, Canny BJ, Gregory JE, Proske U. Large-fiber mechanoreceptors contribute to muscle soreness after eccentric exercise. J Pain 2001;2:209-19.
Submitted Feb 20, 2019; accepted Jun 24, 2019.
ABSTRACT Objective: The purpose of this exploratory study was to determine whether a single session of vibration therapy (VT) would improve muscular and functional performance in individuals with symptomatic peripheral artery disease (PAD). Methods: In a randomized, balanced cross-over design fourteen PAD participants with intermittent claudication (mean 6 standard deviation; age, 73.9 6 4.6 years; height, 172.6 6 68.4 cm; body mass, 85.2 6 15.7 kg) performed VT and control that involved repeated chair rises, timed up-and-go test, and 6-minute walk test. Each intervention was separated by at least 2 days. Wearable VT devices were positioned on the right and left lower limbs that were turned on during functional testing but were turned off for the control intervention. Results: VT significantly improved (P < .05) repeated chair rises and timed up-and-go test compared with control with a small effect size of 0.46 and 0.45, respectively. Similarly, a significant (P < .01) and meaningful change in 6-minute walk test was noted in VT compared with control. Conclusions: This exploratory study suggest that VT may enhance functional strength, mobility, and walking performance by extending the onset of claudication and increasing walking distance in PAD with intermittent claudication. However, further study is required to confirm and extend these preliminary findings and determine the potential mechanisms of action in VT. (J Vasc Surg 2019;-:1-6.) Keywords: Vibration therapy; Intermittent claudication; Stand-to-sit; Timed get-up-and-go; 6-minute walk; Mobility
Peripheral artery disease (PAD) is highly prevalent, costly, and deadly condition that affects 15% to 20% of individuals over 70 years of age.1 The global prevalence of PAD has increased by 23.5% from 2000 to 2010,1 resulting in an increased risk of cardiovascular mortality.2 PAD may be asymptomatic but many people with PAD suffer from limb disability and intermittent claudication (IC), which is characterized by leg pain when walking that is relieved rapidly by resting. Other adverse changes associated with PAD lower limb function include reduced leg strength, impaired balance, slow walking speed, functional decline, and mobility loss.2
From the School of Sport, Exercise and Nutrition, Massey Universitya; and the Department of Vascular, Endovascular and Transplant Surgery, Christchurch Hospital,b and the Department of Surgery, University of Otago, Christchurch.c Funded by Palmerston North Medical Research Foundation. The Foundation has no involvement in the study design; collection, analysis and interpretation; manuscript writing; or the decision to submit the manuscript for publication. Author conflict of interest: none. Correspondence: Darryl J. Cochrane, PhD, School of Sport, Exercise & Nutrition, Massey University, Private Bag 11 222, Palmerston North, New Zealand (e-mail: [email protected]). The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest. 0741-5214 Copyright Ó 2019 by the Society for Vascular Surgery. Published by Elsevier Inc. https://doi.org/10.1016/j.jvs.2019.06.214
Exercise rehabilitation is central to treating IC with revascularization reserved for those who have been unsuccessful with exercise training or have a favorable risk-benefit ratio. Exercise is regarded as a safe and effective treatment for IC where treadmill exercise has reported improved quality of life3 and increased maximal walking distance by 50% to 100%.4 Exercise is seen as an effective noninterventional approach to reducing leg symptoms that are best achieved from supervised exercise programmes.5 Despite this, there is still a lack of specific information about how PAD patients with IC should undertake exercise training.6 Although walking is a common modality to treat IC, the ischemic pain induced by walking may generate frustration and discourage motivation to participate in exercise. This may further reduce physical activity levels through a decline in exercise adherence that results in subsequent functional disability7 and increases the risk of comorbidities associated with IC.8 If an alternative exercise to walking was able to improve functional performance and reduce mobility loss, it would be a welcome addition for symptomatic PAD, especially if the intervention was able to reduce pain and leg symptoms when performing walking and functional activities. One such modality that may assist with this goal is vibration therapy (VT), and we postulate that it may assist people suffering from IC. Acute vibration exposure increases muscle activation,9 blood flow,10 and oxygen uptake,11 which are potentially important in alleviating PAD
1
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symptoms and in multiple sclerosis patients a single vibration session reported improved balance, mobility, and walking.12 Wearable vibration is an emerging technology that has evolved from local vibration, which has relied on hand-held, cabled-powered vibratory; however, wearable vibration allows for greater portability that can be applied to the target muscle with ease. Recently, wearable vibration for 10 minutes (120 Hz) significantly enhanced muscular power in master athletes13 and 15 minutes (120 Hz) of vibration attenuated muscle soreness and improved range of motion after strenuous eccentric exercise of the elbow flexors.14 Thus, a single dose of vibration has scientific merit for therapeutic benefit but currently there is a lack of research to determine the efficacy of VT; therefore, based on the aforementioned scientific evidence, the purpose of this current study was to determine whether a single session of VT may benefit muscular performance in PAD individuals that have IC. It was hypothesized that VT would improve walking performance and functional mobility.
METHODS Study design In a randomized, balanced cross-over design all participants performed vibration therapy (VT) and control (no VT) interventions with at least 2 days separating each intervention, which is sufficient recovery as the benefits of a single session of vibration declines in an hour.15 Every participant completed the following testing order of repeated chair rises (RCR; 2), timed up-and-go test (2), and 6-minute walk test (6-MWT). Between repetitions, 60 and 30 seconds of rest was enforced for RCR and timed up-and-go test, respectively. For VT, the device was turned on at the commencement of the RCR and switched off at the termination of the 6-MWT. For controls, the VT device was placed in the exact position as VT, but it was not turned on during testing. The time to complete VT and control interventions were also recorded. Participants were asked to abstain from alcohol, caffeine, and exercise for 24 hours before testing. To account for daily biorhythms, all testing was conducted at the same time of day and participants were encouraged to maintain their dietary and sleeping habits during the study. Participants Fourteen participants with PAD and IC (femoropopliteal lesion) were previously assessed by a specialist using noninvasive techniques such as magnetic resonance imaging and computed tomography angiography. Participants volunteering for the study had to meet the following criteria: a history of walking leg pain, resting ankle brachial index of less than 0.9, and ambulatory leg pain confirmed by walking exercise. Exclusion criteria included an inability to walk without a walker or
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ARTICLE HIGHLIGHTS d
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Type of Research: Single-center randomized crossover study Key Findings: A single session of vibration therapy improved functional strength (12%), mobility (12%), and walking performance by extending the onset of claudication (63%) and increasing walking distance (13%) in 14 patients with peripheral artery disease and intermittent claudication. Take Home Message: Acute vibration therapy has shown promising results to assisting patients with intermittent claudication in alleviating exertional leg symptoms while performing conventional walking exercise.
wheelchair, severe functional limitation, terminal illness, and recent major operation.16 Further demographic data are included in Table I. Written informed consent was obtained from participants, and ethical approval was granted by the university’s human ethics committee. The sample size of this study was calculated from the primary outcome of 6-MWT. Previous research has indicated that a mean change for between-group comparison of 50 m represents a substantial meaningful difference in the 6-MWT.17 From this, the current study was designed to have 80% power to detect a change of 55 m. Using a paired t test (2-sided, a ¼ .05) with a standard deviation of 65 m, a sample size of 14 participants was required. Measures RCR. Rising to stand from a seated position is a very common task in daily life where, RCR assesses lower limb functional strength18 and is a valid measure of dynamic balance and functional mobility.19 RCR is strongly correlated with the 6-MWT20 and has excellent relative and absolute reliability in older adults.19 Seated in a straight-backed chair (seat height of 42 cm), participants were asked to fold their arms across their chest and ascend to an upright stance before sitting down five consecutive times as quickly as possible. Time was recorded from rising of the first repetition and terminated when returning to a seated position of the fifth repetition. This test was repeated after 60 seconds of rest and the mean of the two attempts were used for analysis. Timed up-and-go test. The timed up-and-go test (TUG) assesses functional mobility21 and has good reliability and validity.22 From a standardized chair (seat height of 42 cm) with each hand placed on the respective thigh, participants ascended and walked 3 m to a cone placed in front of the chair, turned and walked back to the chair to resume a seated position as quickly as possible. Time was recorded from the initial movement to the return of
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Table I. Participant characteristics Age, years No. of participants
73.9 6 4.6 14
Sex Male
86
Female
14
Height, cm
172.6 6 8.4
Weight, kg
85.2 6 15.7
Body mass index
28.7 6 5.5
Resting ABI
0.74 6 20
Unilateral symptoms
29
Bilateral symptoms
71
Current smoker
7
Diabetes mellitus
7
Beta-blocker Antihypertensive agent
7 57
Statin
42
Antiplatelet agenta
64
ABI, Ankle-brachial index. Values are presented as mean 6 standard deviation or percentages. a Aspirin.
the seated position. The test was repeated after 60 seconds of rest and the mean of the two attempts were used for analysis. After the TUG, a 30-second rest was enforced before the 6-MWT. 6-MWT. The self-paced 6-MWT assesses the submaximal level of functional capacity that reflects activities of daily living that are performed at submaximal levels of exertion.23 The 6-MWT is regarded a reliable measure of functional exercise capacity in persons with PAD.24 Following standardized procedures,23 participants were instructed to walk back and forth along a 30-m corridor for 6 minutes continuously with the aim of walking as many laps (covering as much ground) as possible within 6 minutes. Participants were permitted to rest if necessary but were encouraged to continue walking once the claudication pain subsided sufficiently.25 The claudication pain onset time (COT) and claudication pain onset distance (COD) were noted along with the total distance (TD) covered in 6 minutes. Methodology VT. To ensure the greatest vibration response in generating a systemic effect a wearable vibratory device (MyoVolt, Christchurch, New Zealand) was positioned on the lateral, medial gastrocnemius and the intersection of these two muscles of the right and left limb and were held in place by an elastic stocking (Fig). Using the continuous mode the vibration devices were turned on at the commencement of RCR and turned off at the termination of 6-MWT and the exposure time of VT was recorded. When fully charged the Myovolt device can last up to approximately
80 minutes. Each treatment cycle is 10 minutes, when the device automatically switches off; if another cycle is required, the switch can be turned on to reactivate the device. Currently, there is scant research for VT prescription (duration, vibration frequency, and vibration amplitude). However, applying the Myovolt for 10 and 15 minutes at a vibration frequency of 120 Hz has been shown to enhance muscular power in master athletes13 and accelerate muscle recovery after strenuous exercise in physically active males,14 respectively. From these findings, the selection of 120 Hz with an amplitude of 1.2 mm was considered sufficient to elicit the appropriate changes. Controls. For the control condition, the wearable vibratory devices were positioned in the exact position as VT, but were not switched on. The time was also noted from the commencement of RCR to the termination of 6-MWT that allowed a direct comparison with VT time. Statistical analysis All statistical analysis was computed by using Statistical Package for Social Sciences (SPSS, version 23, IBM, Armonk, NY) and all values are presented as mean 6 standard deviation. The level of significance was set at a P value of .05 or less. All data were normally distributed according to Kolmogorov-Smirnov test and sphericity was not violated. Dependent variables (RCR, TUG, COT, COD, and TD) were evaluated with a repeated measure analysis of variance. Where significant F values were achieved, pairwise comparisons were performed using the Bonferroni post hoc procedure. Effect size (mean change/pooled standard deviation) were calculated to quantify the magnitude of the vibration effect on RCR, TUG, COT, COD, and TD. Effect sizes were classified using the following criteria: 0.0, trivial; 0.2, small; 0.6, moderate; 1.2, large; and 2.0, very large.26
RESULTS VT significantly (P < .05) improved RCR and TUG by approximately 12%, with a small effect size of 0.46 and 0.45, respectively (Table II) compared with control. For the 6-MWT, VT significantly (P < .01) enhanced COT (65 seconds), COD (79 m), and TD (48 m) that revealed large (1.25), moderate (1.07), and small (0.33) effect sizes, respectively (Table II) compared with controls. The duration of VT exposure was 9:56 6 0:45 minutes, which was statistically similar (P > .05) to the control duration (9:47 6 0:57 minutes).
DISCUSSION To our knowledge, this is the first study to examine if a single session of VT can improve functional performance and walk time of patients with PAD with IC. These results confirm the hypothesis that VT significantly improved RCR, TUG, and 6-MWT, compared with control. The beneficial effects of exercise in PAD have been well-documented; however, the mechanisms remain
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Fig. Positioning of VT (A) of the right gastrocnemius held in place with an elastic stocking (B).
uncertain.27 Exercise has the ability to improve vascular and skeletal muscle function in PAD.28 Similarly, VT has been reported to increase tissue oxygenation and perfusion in healthy males, making it a viable therapeutic option for PAD to reduce the risk of short-term ischaemia and reperfusion-induced cell damage.29 To date, research has focused on whole-body vibration (WBV) therapy in various populations.30 Given the emergence of wearable vibration as a novel therapy, it could theoretically improve endothelial and neuromuscular function and decrease systemic inflammation. Owing to the scope of the study, these measures were not assessed directly. However, the present findings indicate that RCR and TUG elicited a small meaningful change of 14% and 13%, respectively. This finding is in agreement with earlier WBV studies performed on children with cerebral palsy,31 in multiple sclerosis,32 and for patients with chronic stroke.33 RCR and TUG are measures of lower limb muscle strength and balance21 that are influenced by vibration. Single session WBV studies have revealed increases in muscle strength15 and balance,12,34 although others have failed to show any improvement.35 It has
been suggested that strength and balance improvements are a result of vibration eliciting a neuromuscular response, thereby increasing muscle activity and motor unit recruitment.15,34 The direct application of vibration on muscle is capable of increasing Ia afferent discharge that elicits an excitatory response of the alpha motorneurons,36 which may explain the transient increase in muscle strength.37 This finding has been supported by previous research that reported an enhancement in muscle power following a single session of VT,13 and it plausible that the current wearable VT device was able to exert similar physiologic changes to improve RCR and TUF. Similarly, direct vibration has the capacity to influence other body receptors that are likely to improve balance.12 It is unclear of how long the beneficial effects last after a bout of vibration, but WBV research from young healthy adults reported a transient (after 2 minutes) improvement in lower limb muscle performance that returned to baseline at 60 minutes.15 Similarly, in stroke patients, knee extension strength and muscle activity increased 5 to 10 minutes after a single session of WBV.38 Therefore,
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Table II. Control and vibration therapy (VT) 6-MWT RCR, seconds
TUG, seconds
COT, seconds
COD, meters
TD, meters
Control
14.23 6 4.04
8.69 6 2.08
102 6 36
125.14 6 50.94
358.43 6 142.36
VT
12.49 6 3.48a
7.67 6 2.45a
167 6 63b
204.29 6 91.16b
406.29 6 143.66b
Change
1.74 6 2.63
1.02 6 1.34
65 6 32
79.14 6 50.89
47.86 6 24.06
0.46
0.45
1.25
1.07
0.33
(VT-Control) ES
6-MWT, 6-minute walk test; COD, claudication pain onset distance; COT, claudication pain onset time; ES, effect size; RCR, repeated chair rises; TD, total distance; TUG, timed up-and-go. Values are presented as mean 6 standard deviation. a P < .05 compared with control. b P < .01 compared with control.
it is plausible that patients with IC would not have to wear the VT device while walking; it could be passively administered and over a longer period of exposure it may provide gradual and sustained improvement. Evidence to support this finding indicates that long-term vibration training (3 wk1 for 8 weeks) in older people improved muscle strength, gait, and TUG compared with a control group, and was comparable with changes recorded from the exercise group.39 The current results illustrate VT produced a large meaningful improvement in COT and COD, whereas a small meaningful change was recorded for TD during 6-MWT. A possible explanation for the current improvement in 6-MWT may be in part due to the potentiation of neuromuscular properties of neurogenic excitability40 and/or muscle tuning.41 This acute change would translate to assisting the control and execution of walking performance. Other factors, such as increased blood flow and muscle tissue oxygenation may also contribute to enhancing 6-MWT. A single session of localized vibration applied to the plantar area of the foot has been shown to calf blood flow.42 Equally, muscle tissue oxygenation is increased during a single session of WBV.29 Consequently, the current VT may have elevated blood flow and tissue oxygenation resulting greater muscle perfusion that would assist walking performance; however, this finding requires further research to substantiate this claim. Finally, applying vibration has been shown to decrease acute musculoskeletal pain43 and reduce pain caused by muscle pressure.44 Therefore, VT may have the capacity to decrease or mask the perception of pain while performing the 6-MWT.
CONCLUSIONS A single session of wearable VT significantly improved functional performance measures of RCR, TUG, and 6MWT. The clinical significance of the small and large meaningful changes suggests that VT may acutely assist PAD patients with IC. Given the ease of use and portability of VT it may improve exercise tolerance by improving functional strength, mobility and extending the onset of claudication and increase walking distance;
however, a randomized clinical training study is required to fully understand the efficacy of VT by comparing it to traditional exercise, such as walking. We are grateful to the participants who gave their time and to the Department of Physiotherapy, Christchurch Hospital for the use of their facilities and Palmerston North Medical Research Foundation for funding this study.
AUTHOR CONTRIBUTIONS Conception and design: DC, JR Analysis and interpretation: DC, JR Data collection: DC, FC Writing the article: DC Critical revision of the article: DC, FC, JR Final approval of the article: DC, FC, JR Statistical analysis: DC Obtained funding: DC Overall responsibility: DC
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Submitted Feb 20, 2019; accepted Jun 24, 2019.