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Acute effects of whole body vibration on heart rate variability in elderly people
Journal of Bodywork & Movement Therapies xxx (2017) 1e4
Contents lists available at ScienceDirect
Journal of Bodywork & Movement Therapies journal homepage: www.elsevier.com/jbmt
Pilot Study
Acute effects of whole body vibration on heart rate variability in elderly people Maria das Graças Bastos Licurci*, Alessandra de Almeida Fagundes, Emilia Angela Lo Schiavo Arisawa Cardiopulmonary Rehabilitation Laboratory, Science Health Faculty, Vale of Paraiba University (UNIVAP), Brazil
a r t i c l e i n f o
a b s t r a c t
Article history: Received 4 May 2017 Received in revised form 19 September 2017 Accepted 4 October 2017
Background: Whole body vibration (WBV) has been widely used as a modality for physical activity. In fact, WBV has been used for physical rehabilitation, and to improve muscle performance; but there is little information about its effects on heart rate variability (HRV). Aim: The aim of this study was to evaluate the effect of vibration on HRV of the elderly using the vibratory platform. Methods: Eleven older adults (7 men, 4 women), aged between 60 and 75 years, were subjected to WBV. The study consisted of a single session of WBV with volunteers standing upright for 10 min on the oscillating platform, with frequency of vibration set at 20 Hz (displacement ± 6 mm; orbital vibration). Pre (baseline) and post-WBV electrocardiograph signals were acquired using a cardiac monitor; and data were statistically analyzed using paired Student's t-test or Wilcoxon test, as appropriate. Results: The results demonstrated an increase in SDNN (standard deviation (SD) beat-to-beat, NeN intervals), rMSSD (square root of the mean squared difference of successive NeNs) and pNN50 (proportion of NeN50 divided by total number of NeNs) post WBV (p ¼ 0.032, p ¼ 0.024 e p ¼ 0.044, respectively), compared to baseline. The present study thus demonstrated that time domain variables (i.e., SDNN, rMSSD, and pNN50) increase post WBV. Conclusions: Older individuals are at high risk of developing cardiovascular diseases. As seen in the study, WBV improves HRV; and may help reduce risk of cardiac ailments. Moreover, WBV does not require extensive physical activity on the part of the participant. This makes WBV potentially beneficial to the elderly population. Further studies on WBV using different frequencies and training schedules may improve its applicability in clinics. © 2017 Elsevier Ltd. All rights reserved.
Keywords: Whole body vibration Elderly Aged Heart rate variability
1. Introduction Physical activity is important in delaying the deleterious effects of aging. The vibratory platform has been widely used as a form of physical activity for elderly population. Vibration can be understood as the alternating movement of a solid body in relation to its center of equilibrium (Aitj a-rabert et al., 2012; Bogaerts et al., 2009). There are vibration-producing devices available in the market that are used for physical rehabilitation and improving physical performance. These platforms emit constant bell-shaped
* Corresponding author. E-mail address: [email protected] (M.G.B. Licurci).
vibrations, which produces symmetrical waves. This makes it possible to quantify the intensity of the vibration produced by the apparatus, using the oscillation amplitude (Behboudi et al., 2011; Theodorou et al., 2015). The amplitude is calculated as half the difference between the largest and the smallest displacement value occurring during the oscillation and is reported in millimeters (mm). The frequency of vibration refers to the rate of repetitions of displacements, so it is measured in Hertz (Hz) which are cycles per second (Chen et al., 2014). For example, when a platform works with 5 mm amplitude and 30 Hz frequency, it means that this unit is moving 5 mm around a fixed point and that displacement occurs 30 times in a second (Silva and Schneider, 2011). Heart Rate Variability (HRV) is the measure of variation in instantaneous heart rate time series reflected by beat to beat RR-
https://doi.org/10.1016/j.jbmt.2017.10.004 1360-8592/© 2017 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Licurci, M.d.G.B., et al., Acute effects of whole body vibration on heart rate variability in elderly people, Journal of Bodywork & Movement Therapies (2017), https://doi.org/10.1016/j.jbmt.2017.10.004
2
M.G.B. Licurci et al. / Journal of Bodywork & Movement Therapies xxx (2017) 1e4
intervals. It gives an idea of balance between the slow acting sympathetic and fast acting parasympathetic systems, and can be used to evaluate cardiovascular ailments. The current study aims to investigate the effects of WBV on HRV in older adults.
50 ms (NeN50); proportion of NeN50 divided by total number of NeNs (pNN50); and square root of the mean squared difference of successive NeNs (rMSSD). 2.3. Data analysis
2. Methods 2.1. Design Eleven healthy elderly subjects (7 men, 4 women) aged between 60 and 75 years, participated in this study. Medical history of all prospective participants was thoroughly checked, and only those deemed ‘healthy’ were enrolled into the study. Healthy is defined as those devoid of any disease and risk factor, and exhibiting a normal walking gait. Individuals with major trauma, systemic disease, conflicting or ongoing treatments (e.g. cardio-depressive and cardio-stimulating medications), tobacco users, and those who could not understand the maneuvers were excluded from the study. The study was approved by the Ethics Committee in Research of University of Paraiba Valley (ECR/UNIVAP, opinion number 1.395.981, protocol number CAEE. 51246815.0.0000.5503, Brazil). Subject recruitment was random, and from a pool of elderly people invited to participate in the study at Healthy Science Faculty (UNIVAP). Written informed consent was obtained from all participants after being informed regarding the study aims and procedures. 2.2. Intervention protocol Electrocardiographic signals were recorded using a cardiac monitor (RS800, Polar Electro, Finland) from subjects for 10 min (baseline) before WBV. They were then subjected to a single 10 min WBV session standing upright on oscillating platform (Vibra 6 mm, ~o Nissan®, Sa Paulo, Brazil) vibrating at 20 Hz (displacement ± 6 mm; orbital vibration). Post WBV, electrocardiographic signals were collected again immediately. The signals were filtered using Polar Pro Training Software (Polar Electro®, Kempele, Finland) and analyzed using HRV Analysis Software v2.0 (University of Western Finland, Finland) for time domain and frequency. All participants were requested to sit in the same sitting position before the study. Baseline data from all participants were acquired after 10 min adaptation. The entire experiment was performed for all participants at the same time of the day. These precautions were taken to avoid variations due to circadian rhythm, body position, and prior activity level. Since subjects on medication were excluded from the study, the influence of the same on results was also avoided. For frequency-domain HRV analysis, Fast Fourier Transform was used to calculate the very lowefrequency (VLF, 0e0.04 Hz), lowfrequency (LF, 0.04e0.15 Hz), and high-frequency (HF, 0.15e0.4 Hz) components, as well as LF and HF components in normalized units (LFun and HFun, respectively). LF and HF were considered to reflect sympathetic and parasympathetic activity, respectively. The autonomic balance was obtained by the ratio between the sympathetic and parasympathetic areas (LF/HF); wherein ratios >1, <1 and 1 were indicative of sympatheticotonia, vagotonia, and sympathovagal balance, respectively. VLF is not a well-defined physiological phenomenon and may be related to the renineangiotensinealdosterone system, thermoregulation, and peripheral vasomotor tone (Task Force, 1996). For the HRV time-domain analysis, the following variables were calculated: average normal ReR intervals (RRmed); standard deviation (SD) beat-to-beat (NeN) intervals (SDNN, measured in ms); number of pairs of successive NeNs that differed by more than
Statistical analysis was carried out using a commercial statistical program (Sigma Plot 11.0, Systat®, Chigado, IL, USA). Normality of the distributions was tested by Kolmogorov-Smirnov test. Statistical comparisons between baseline and post-WBV were made using paired Student's t-test or Wilcoxon, as appropriate; and reported as mean ± SD. The level of significance was set at p < 0.05. 3. Results The flowchart depicted in Fig. 1 shows the recruitment rates, drop-offs and refusals. Of 31 individuals, 20 refused to participate for personal reasons and 1 individual was excluded because the inclusion criteria were not fulfilled (see Fig. 1). With the purpose of determining the effect of WBV on HRV, 11 older adults were subjected to 10 min WBV as described earlier. Baseline and post-WBV, electrocardiograph signals were collected and results expressed as their mean and respective Standard Deviations (SDs). Table 1 shows the results of anthropometric data. It is possible to observe that the individuals had body mass index corresponding to overweight (BMI ¼ 27.48). All results are reported in Table 2. SDNN, rMSSD and pNN50 increased post WBV compared to baseline (p ¼ 0.032, p ¼ 0.024 and p ¼ 0.044, respectively). None of the data in frequency domain showed any difference (see Table 2). 4. Discussion WBV is a well-known method for improving muscle performance and bone density, indicating that it may be an effective mez-Cabello et al., 2014; Brummel-Smith exercise modality (Go et al., 2017; Perchthaler et al., 2015). There is a considerable amount of data which supports the beneficial effects of WBV in the general population. In the elderly, it has been reported that WBV promotes positive effects on postural control and walking ability (Zhang et al., 2014). But, its effects on HRV of sn elderly population remain unclear (Zhang et al., 2014; Osugi et al., 2014). Preliminary research suggests that WBV can influence HRV (Sanudo et al., 2013, Severino et al., 2016, Wong et al., 2016). Wong et al. (2016) reported that WBV training consisting of static and dynamic leg exercises with vertical vibration at 25e40 Hz for 8 weeks improve sympathovagal balance in sedentary obese postmenopausal women. Similarly, Severino et al. (2016) evaluated the effects of a 6-week WBV training regimen on HRV and body composition in obese postmenopausal women. The authors suggested that WBV training improves HRV and body fat percentage in that population. In addition, they correlated the changes in sympathovagal balance with body fat percentage. There are some methodological differences between the present study and those mentioned above; such as the WBV training duration and body mass index (BMI) of the population studied. Wong et al. (2016) and Severino et al. (2016) examined the effects of more than 6 weeks long WBV training on HRV in obese women. In contrast to both these studies, the current investigation reports the immediate effects of a single 10 min session of WBV in non-obese elderly population; and finds improvement in HRV. This indicates that changes in BMI may not be solely responsible for HRV improvement, as suggested by Severino et al. (2016); but other factors may be involved. In the present study, the time domain components of HRV such
Please cite this article in press as: Licurci, M.d.G.B., et al., Acute effects of whole body vibration on heart rate variability in elderly people, Journal of Bodywork & Movement Therapies (2017), https://doi.org/10.1016/j.jbmt.2017.10.004
M.G.B. Licurci et al. / Journal of Bodywork & Movement Therapies xxx (2017) 1e4
3
Fig. 1. Flowchart of subjects who met inclusion/exclusion criteria for the study population.
Table 1 Participants’ characteristics in relation to anthropometric data and age (n ¼ 11). Participants' Characteristics
Average ± SD
Age (years) Weight (Kg) Height (cm) BMI (Kg/m2)
64.18 ± 4.37 76.68 ± 7.28 167 ± 9.20 27.48 ± 2.32
SD, standard deviation, BMI, body mass index, Kg, kilogram, cm, centimeter, kg/m2 kilogram per square meter.
as SDNN, rMSSD and pNN50 showed statistically significant increase post WBV (see Table 2). SDNN index increase indicates increased HRV; and consequently, a decreased cardiac risk for elderly (Severino et al., 2016). The rMSSD index reflects parasympathetic modulation, and is used to evaluate the autonomic variation in 24 h, being influenced mainly by the vagal system. Values below 15 ms were considered as high risk (sympathetic predominance) and above 39 ms as low risk (vagal predominance). Normal values of rMSSD must be between 15 ms and 39 ms. This study observed normal values of rMSSD at baseline (17.35 ± 10.01) and post WBV (20.69 ± 10.55). However, the increase in rMSSD post WBV is statistically significant (p ¼ 0.024); suggesting a possible influence on parasympathetic modulation (see Table 2) (Machado-Vidotti et al., 2014).
Table 2 Heart rate variability in time and frequency domain at baseline and post WBV (n ¼ 11). Time Domain
Pre
Post
p value
HR mean(bpm) RR mean SDNN (ms) rMSSD (ms) pNN50 (%) Frequency Domain HF (%) LF (%) VLF (%) LF/HF LFun HFun
77.72 ± 10.13 786.12 ± 103.93 37.30 ± 14.34 17.35 ± 10.01 2.63 ± 3.99
75.61 ± 10.26 809.60 ± 111.96 43.75 ± 13.91 20.69 ± 10.55 4.00 ± 5.19
0.017* 0.021* 0.032* 0.024* 0.044*
7.46 ± 3.90 40.57 ± 18.96 57.05 ± 16.52 8.55 ± 9.49 81.60 ± 11.44 17.53 ± 10.02
16.76 ± 30.17 34.27 ± 13.94 58.03 ± 14.24 6.60 ± 6.64 73.89 ± 22.74 19.6 ± 11.40
0.57 0.33 0.82 0.27 0.06 0.55
All values are mean e standard deviation (SD). * p value ≤ 0.05. Legend: bpm, beats/minHF, high frequency; LF, low frequency; VLF, very low frequency; LF/HF, low frequency/high frequency ratio; LFun, normalized low frequency; HFun, normalized high frequency; rMSSD, square root of the sum of successive differences between adjacent normal ReR intervals squared; pNN50, percentage of normal ReR intervals differing >50 ms of the adjacent ReR; RRmed, average of normal ReR intervals; SDNN, SD of the range NeN, measured in ms.
pNN50 value of less than 5% is indicative of greater sympathetic modulation (Task Force, 1996). The study found pNN50 of less than 5% at baseline (2.63 ± 3.99) and post WBV (4.00 ± 5.19), suggesting a sympathetic predominance. Lower parasympathetic modulation
Please cite this article in press as: Licurci, M.d.G.B., et al., Acute effects of whole body vibration on heart rate variability in elderly people, Journal of Bodywork & Movement Therapies (2017), https://doi.org/10.1016/j.jbmt.2017.10.004
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M.G.B. Licurci et al. / Journal of Bodywork & Movement Therapies xxx (2017) 1e4
(or greater sympathetic modulation) is indicative of increased cardiac risk. The fact that WBV significantly increased pNN50 (p ¼ 0.044), may suggest a protective effect. However, the results of this study have not shown any significant alterations in frequency domain variables of HRV. This finding was similar to a report by Sanudo et al. (2013); which reported no effect on power spectral components of HRV due to passive WBV after an exhaustive bicycle exercise test, despite a reduction on heart rate and an increase in total power. Owing to the small sample size of the present study and lack of matched control group, influence of non-training related factors like placebo effects cannot be dismissed. So, the interpretation of the changes observed is limited, making it difficult to make definitive statements. Studies with larger sample size needs to be carried out to confirm these results. Nevertheless, the preliminary results are interesting. The present study has demonstrated that time domain variables, i. e SDNN, rMSSD and pNN50, increase post WBV; suggesting that this nonconventional exercise modality improves HRV (see Table 2). Moreover, WBV does not require extensive physical activity on the part of the participant. This makes WBV potentially beneficial to the elderly population, who cannot be subjected to extensive effort, and are at high risk of developing cardiovascular diseases. Further studies on WBV using different frequencies and training schedules may improve its applicability in clinics. Financial support None. Conflict of interest statement There were no funding or financial or benefits to the authors. This paper has not been presented in the past in any form. No conflicts of interest have been reported by the authors or by any individuals in control of the content of this article. Acknowledgments We would like to thank all subjects for participating in this study.
References -rabert, M., Rigau, D., Vanmeerghaeghe, A.F., Romero-rodriguez, D., Aitja Subirana, M.B., Bonfill, X., 2012. Efficacy of whole body vibration exercise in older people: a systematic review. J. DisabilRehabil. 34 (11), 883e893. Behboudi, L., Azarbayjani, M.A., Aghaalinejad, H., Salavati, M., 2011. Effects of aerobic exercise and whole body vibration on glycaemia control in type 2 diabetic males. Asian J. Sports Med. 2 (2), 83e90. Bogaerts, A.C., Delecluse, C., Claessens, A.L., Troosters, T., Boonen, S., Verschueren, S.M., 2009. Effects of whole body vibration training on cardiorespiratory fitness and muscle strength in older individuals (a 1-year randomised controlled trial). Age Ageing 38, 448e454. Brummel-Smith, K., Pei-Yang, L., Jasminka, I., 2017. Aerobic exercise and whole-body vibration in offsetting bone loss in older adults. J. Aging Res. 2011, 1e9. Chen, C.H., Liu, C., Chuang, L., Chung, P., Shian, T., 2014. Chronic effects of wholebody vibration on jumping performance and body balance using different frequencies and amplitudes with identical acceleration load. J. Sci. Med. Sport. 17, 107e112. mez-Cabello, A., Gonza lez-Agüero, A., Morales, S., Ara, I., Casajús, J.A., VicenteGo Rodríguez, G., 2014. Effects of a short-term whole body vibration intervention on bone mass and structure in elderly people. J. Sci. Med. Sport 17 (2), 160e164. ~es, R.P., Simo ~es, V.C., Catai, A.M., BorghiMachado-Vidotti, H.G., Mendes, R.G., Simo Silva, A., 2014. Cardiac autonomic responses during upper versus lower limb resistance exercise in healthy elderly men. Braz J. Phys. Ther. 18 (1), 9e18. Osugi, T., Iwamoto, J., Yamazaki, M., Takakuwa, M., 2014. Effect of a combination of whole body vibration exercise and squat training on body balance, muscle power, and walking ability in the elderly. TherClin Risk Manag. 10, 131e138. Perchthaler, D., Grau, S., Hein, T., 2015. Evaluation of a six-week whole-body vibration intervention on neuromuscular performance in older adults. J. Strength Cond. Res. 29 (1), 86e95. Sanudo, B., Cesar-Castillo, M., Tejero, S., Nunes, N., de Hoyo, M., Figueroa, A., 2013. Cardiac autonomic response during recovery from a maximal exercise using whole body vibration. ComplemTherMed 21 (4), 294e299. Severino, G., Sanchez-Gonzalez, M., Walters-Edwards, M., Nordvall, M., Chernykh, O., Adames, J., Wong, A., 2016. Whole-body vibration training improves heart rate variability and body fat percentage in obese hispanic postmenopausal women. J. Aging Phys. Act. 1e25. Silva, P.Z., Schneider, R.H., 2011. Effects of a whole body vibrating plataform on postural balance in elderly people. ActaFisiatr 18 (1), 21e26. Task Force, 1996. Heart rate variability. standards of measurement, physiological interpretation, and clinical use. task force of the european society of cardiology and the North American society of pacing and electrophysiology. Eur. Heart J. 17 (3), 354e381. Theodorou, A., Gerodimos, V., Karatrantou, K., Paschalis, V., Chanou, K., Jamurtas, A., 2015. Acute and chronic whole-body vibration exercise does not induce healthpromoting effects on blood profile. J. Hum. Kinet. 46, 107e118. Wong, A., Alvarez-Alvarado, S., Kinsey, A.W., Figueroa, A., 2016. Whole-body vibration exercise therapy improves cardiac autonomic function and blood pressure in obese pre-and stage 1 hypertensive postmenopausal women. J. AltCompl Med. 22 (12), 970e976. Zhang, L., Weng, C., Liu, M., Wang, Q., Liu, L., He, Y., 2014. Effect of whole-body vibration exercise on mobility, balance ability and general health status in frail elderly patients: a pilot randomized controlled trial. ClinRehabil 28 (1), 59e68.
Please cite this article in press as: Licurci, M.d.G.B., et al., Acute effects of whole body vibration on heart rate variability in elderly people, Journal of Bodywork & Movement Therapies (2017), https://doi.org/10.1016/j.jbmt.2017.10.004
Contents lists available at ScienceDirect
Journal of Bodywork & Movement Therapies journal homepage: www.elsevier.com/jbmt
Pilot Study
Acute effects of whole body vibration on heart rate variability in elderly people Maria das Graças Bastos Licurci*, Alessandra de Almeida Fagundes, Emilia Angela Lo Schiavo Arisawa Cardiopulmonary Rehabilitation Laboratory, Science Health Faculty, Vale of Paraiba University (UNIVAP), Brazil
a r t i c l e i n f o
a b s t r a c t
Article history: Received 4 May 2017 Received in revised form 19 September 2017 Accepted 4 October 2017
Background: Whole body vibration (WBV) has been widely used as a modality for physical activity. In fact, WBV has been used for physical rehabilitation, and to improve muscle performance; but there is little information about its effects on heart rate variability (HRV). Aim: The aim of this study was to evaluate the effect of vibration on HRV of the elderly using the vibratory platform. Methods: Eleven older adults (7 men, 4 women), aged between 60 and 75 years, were subjected to WBV. The study consisted of a single session of WBV with volunteers standing upright for 10 min on the oscillating platform, with frequency of vibration set at 20 Hz (displacement ± 6 mm; orbital vibration). Pre (baseline) and post-WBV electrocardiograph signals were acquired using a cardiac monitor; and data were statistically analyzed using paired Student's t-test or Wilcoxon test, as appropriate. Results: The results demonstrated an increase in SDNN (standard deviation (SD) beat-to-beat, NeN intervals), rMSSD (square root of the mean squared difference of successive NeNs) and pNN50 (proportion of NeN50 divided by total number of NeNs) post WBV (p ¼ 0.032, p ¼ 0.024 e p ¼ 0.044, respectively), compared to baseline. The present study thus demonstrated that time domain variables (i.e., SDNN, rMSSD, and pNN50) increase post WBV. Conclusions: Older individuals are at high risk of developing cardiovascular diseases. As seen in the study, WBV improves HRV; and may help reduce risk of cardiac ailments. Moreover, WBV does not require extensive physical activity on the part of the participant. This makes WBV potentially beneficial to the elderly population. Further studies on WBV using different frequencies and training schedules may improve its applicability in clinics. © 2017 Elsevier Ltd. All rights reserved.
Keywords: Whole body vibration Elderly Aged Heart rate variability
1. Introduction Physical activity is important in delaying the deleterious effects of aging. The vibratory platform has been widely used as a form of physical activity for elderly population. Vibration can be understood as the alternating movement of a solid body in relation to its center of equilibrium (Aitj a-rabert et al., 2012; Bogaerts et al., 2009). There are vibration-producing devices available in the market that are used for physical rehabilitation and improving physical performance. These platforms emit constant bell-shaped
* Corresponding author. E-mail address: [email protected] (M.G.B. Licurci).
vibrations, which produces symmetrical waves. This makes it possible to quantify the intensity of the vibration produced by the apparatus, using the oscillation amplitude (Behboudi et al., 2011; Theodorou et al., 2015). The amplitude is calculated as half the difference between the largest and the smallest displacement value occurring during the oscillation and is reported in millimeters (mm). The frequency of vibration refers to the rate of repetitions of displacements, so it is measured in Hertz (Hz) which are cycles per second (Chen et al., 2014). For example, when a platform works with 5 mm amplitude and 30 Hz frequency, it means that this unit is moving 5 mm around a fixed point and that displacement occurs 30 times in a second (Silva and Schneider, 2011). Heart Rate Variability (HRV) is the measure of variation in instantaneous heart rate time series reflected by beat to beat RR-
https://doi.org/10.1016/j.jbmt.2017.10.004 1360-8592/© 2017 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Licurci, M.d.G.B., et al., Acute effects of whole body vibration on heart rate variability in elderly people, Journal of Bodywork & Movement Therapies (2017), https://doi.org/10.1016/j.jbmt.2017.10.004
2
M.G.B. Licurci et al. / Journal of Bodywork & Movement Therapies xxx (2017) 1e4
intervals. It gives an idea of balance between the slow acting sympathetic and fast acting parasympathetic systems, and can be used to evaluate cardiovascular ailments. The current study aims to investigate the effects of WBV on HRV in older adults.
50 ms (NeN50); proportion of NeN50 divided by total number of NeNs (pNN50); and square root of the mean squared difference of successive NeNs (rMSSD). 2.3. Data analysis
2. Methods 2.1. Design Eleven healthy elderly subjects (7 men, 4 women) aged between 60 and 75 years, participated in this study. Medical history of all prospective participants was thoroughly checked, and only those deemed ‘healthy’ were enrolled into the study. Healthy is defined as those devoid of any disease and risk factor, and exhibiting a normal walking gait. Individuals with major trauma, systemic disease, conflicting or ongoing treatments (e.g. cardio-depressive and cardio-stimulating medications), tobacco users, and those who could not understand the maneuvers were excluded from the study. The study was approved by the Ethics Committee in Research of University of Paraiba Valley (ECR/UNIVAP, opinion number 1.395.981, protocol number CAEE. 51246815.0.0000.5503, Brazil). Subject recruitment was random, and from a pool of elderly people invited to participate in the study at Healthy Science Faculty (UNIVAP). Written informed consent was obtained from all participants after being informed regarding the study aims and procedures. 2.2. Intervention protocol Electrocardiographic signals were recorded using a cardiac monitor (RS800, Polar Electro, Finland) from subjects for 10 min (baseline) before WBV. They were then subjected to a single 10 min WBV session standing upright on oscillating platform (Vibra 6 mm, ~o Nissan®, Sa Paulo, Brazil) vibrating at 20 Hz (displacement ± 6 mm; orbital vibration). Post WBV, electrocardiographic signals were collected again immediately. The signals were filtered using Polar Pro Training Software (Polar Electro®, Kempele, Finland) and analyzed using HRV Analysis Software v2.0 (University of Western Finland, Finland) for time domain and frequency. All participants were requested to sit in the same sitting position before the study. Baseline data from all participants were acquired after 10 min adaptation. The entire experiment was performed for all participants at the same time of the day. These precautions were taken to avoid variations due to circadian rhythm, body position, and prior activity level. Since subjects on medication were excluded from the study, the influence of the same on results was also avoided. For frequency-domain HRV analysis, Fast Fourier Transform was used to calculate the very lowefrequency (VLF, 0e0.04 Hz), lowfrequency (LF, 0.04e0.15 Hz), and high-frequency (HF, 0.15e0.4 Hz) components, as well as LF and HF components in normalized units (LFun and HFun, respectively). LF and HF were considered to reflect sympathetic and parasympathetic activity, respectively. The autonomic balance was obtained by the ratio between the sympathetic and parasympathetic areas (LF/HF); wherein ratios >1, <1 and 1 were indicative of sympatheticotonia, vagotonia, and sympathovagal balance, respectively. VLF is not a well-defined physiological phenomenon and may be related to the renineangiotensinealdosterone system, thermoregulation, and peripheral vasomotor tone (Task Force, 1996). For the HRV time-domain analysis, the following variables were calculated: average normal ReR intervals (RRmed); standard deviation (SD) beat-to-beat (NeN) intervals (SDNN, measured in ms); number of pairs of successive NeNs that differed by more than
Statistical analysis was carried out using a commercial statistical program (Sigma Plot 11.0, Systat®, Chigado, IL, USA). Normality of the distributions was tested by Kolmogorov-Smirnov test. Statistical comparisons between baseline and post-WBV were made using paired Student's t-test or Wilcoxon, as appropriate; and reported as mean ± SD. The level of significance was set at p < 0.05. 3. Results The flowchart depicted in Fig. 1 shows the recruitment rates, drop-offs and refusals. Of 31 individuals, 20 refused to participate for personal reasons and 1 individual was excluded because the inclusion criteria were not fulfilled (see Fig. 1). With the purpose of determining the effect of WBV on HRV, 11 older adults were subjected to 10 min WBV as described earlier. Baseline and post-WBV, electrocardiograph signals were collected and results expressed as their mean and respective Standard Deviations (SDs). Table 1 shows the results of anthropometric data. It is possible to observe that the individuals had body mass index corresponding to overweight (BMI ¼ 27.48). All results are reported in Table 2. SDNN, rMSSD and pNN50 increased post WBV compared to baseline (p ¼ 0.032, p ¼ 0.024 and p ¼ 0.044, respectively). None of the data in frequency domain showed any difference (see Table 2). 4. Discussion WBV is a well-known method for improving muscle performance and bone density, indicating that it may be an effective mez-Cabello et al., 2014; Brummel-Smith exercise modality (Go et al., 2017; Perchthaler et al., 2015). There is a considerable amount of data which supports the beneficial effects of WBV in the general population. In the elderly, it has been reported that WBV promotes positive effects on postural control and walking ability (Zhang et al., 2014). But, its effects on HRV of sn elderly population remain unclear (Zhang et al., 2014; Osugi et al., 2014). Preliminary research suggests that WBV can influence HRV (Sanudo et al., 2013, Severino et al., 2016, Wong et al., 2016). Wong et al. (2016) reported that WBV training consisting of static and dynamic leg exercises with vertical vibration at 25e40 Hz for 8 weeks improve sympathovagal balance in sedentary obese postmenopausal women. Similarly, Severino et al. (2016) evaluated the effects of a 6-week WBV training regimen on HRV and body composition in obese postmenopausal women. The authors suggested that WBV training improves HRV and body fat percentage in that population. In addition, they correlated the changes in sympathovagal balance with body fat percentage. There are some methodological differences between the present study and those mentioned above; such as the WBV training duration and body mass index (BMI) of the population studied. Wong et al. (2016) and Severino et al. (2016) examined the effects of more than 6 weeks long WBV training on HRV in obese women. In contrast to both these studies, the current investigation reports the immediate effects of a single 10 min session of WBV in non-obese elderly population; and finds improvement in HRV. This indicates that changes in BMI may not be solely responsible for HRV improvement, as suggested by Severino et al. (2016); but other factors may be involved. In the present study, the time domain components of HRV such
Please cite this article in press as: Licurci, M.d.G.B., et al., Acute effects of whole body vibration on heart rate variability in elderly people, Journal of Bodywork & Movement Therapies (2017), https://doi.org/10.1016/j.jbmt.2017.10.004
M.G.B. Licurci et al. / Journal of Bodywork & Movement Therapies xxx (2017) 1e4
3
Fig. 1. Flowchart of subjects who met inclusion/exclusion criteria for the study population.
Table 1 Participants’ characteristics in relation to anthropometric data and age (n ¼ 11). Participants' Characteristics
Average ± SD
Age (years) Weight (Kg) Height (cm) BMI (Kg/m2)
64.18 ± 4.37 76.68 ± 7.28 167 ± 9.20 27.48 ± 2.32
SD, standard deviation, BMI, body mass index, Kg, kilogram, cm, centimeter, kg/m2 kilogram per square meter.
as SDNN, rMSSD and pNN50 showed statistically significant increase post WBV (see Table 2). SDNN index increase indicates increased HRV; and consequently, a decreased cardiac risk for elderly (Severino et al., 2016). The rMSSD index reflects parasympathetic modulation, and is used to evaluate the autonomic variation in 24 h, being influenced mainly by the vagal system. Values below 15 ms were considered as high risk (sympathetic predominance) and above 39 ms as low risk (vagal predominance). Normal values of rMSSD must be between 15 ms and 39 ms. This study observed normal values of rMSSD at baseline (17.35 ± 10.01) and post WBV (20.69 ± 10.55). However, the increase in rMSSD post WBV is statistically significant (p ¼ 0.024); suggesting a possible influence on parasympathetic modulation (see Table 2) (Machado-Vidotti et al., 2014).
Table 2 Heart rate variability in time and frequency domain at baseline and post WBV (n ¼ 11). Time Domain
Pre
Post
p value
HR mean(bpm) RR mean SDNN (ms) rMSSD (ms) pNN50 (%) Frequency Domain HF (%) LF (%) VLF (%) LF/HF LFun HFun
77.72 ± 10.13 786.12 ± 103.93 37.30 ± 14.34 17.35 ± 10.01 2.63 ± 3.99
75.61 ± 10.26 809.60 ± 111.96 43.75 ± 13.91 20.69 ± 10.55 4.00 ± 5.19
0.017* 0.021* 0.032* 0.024* 0.044*
7.46 ± 3.90 40.57 ± 18.96 57.05 ± 16.52 8.55 ± 9.49 81.60 ± 11.44 17.53 ± 10.02
16.76 ± 30.17 34.27 ± 13.94 58.03 ± 14.24 6.60 ± 6.64 73.89 ± 22.74 19.6 ± 11.40
0.57 0.33 0.82 0.27 0.06 0.55
All values are mean e standard deviation (SD). * p value ≤ 0.05. Legend: bpm, beats/minHF, high frequency; LF, low frequency; VLF, very low frequency; LF/HF, low frequency/high frequency ratio; LFun, normalized low frequency; HFun, normalized high frequency; rMSSD, square root of the sum of successive differences between adjacent normal ReR intervals squared; pNN50, percentage of normal ReR intervals differing >50 ms of the adjacent ReR; RRmed, average of normal ReR intervals; SDNN, SD of the range NeN, measured in ms.
pNN50 value of less than 5% is indicative of greater sympathetic modulation (Task Force, 1996). The study found pNN50 of less than 5% at baseline (2.63 ± 3.99) and post WBV (4.00 ± 5.19), suggesting a sympathetic predominance. Lower parasympathetic modulation
Please cite this article in press as: Licurci, M.d.G.B., et al., Acute effects of whole body vibration on heart rate variability in elderly people, Journal of Bodywork & Movement Therapies (2017), https://doi.org/10.1016/j.jbmt.2017.10.004
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M.G.B. Licurci et al. / Journal of Bodywork & Movement Therapies xxx (2017) 1e4
(or greater sympathetic modulation) is indicative of increased cardiac risk. The fact that WBV significantly increased pNN50 (p ¼ 0.044), may suggest a protective effect. However, the results of this study have not shown any significant alterations in frequency domain variables of HRV. This finding was similar to a report by Sanudo et al. (2013); which reported no effect on power spectral components of HRV due to passive WBV after an exhaustive bicycle exercise test, despite a reduction on heart rate and an increase in total power. Owing to the small sample size of the present study and lack of matched control group, influence of non-training related factors like placebo effects cannot be dismissed. So, the interpretation of the changes observed is limited, making it difficult to make definitive statements. Studies with larger sample size needs to be carried out to confirm these results. Nevertheless, the preliminary results are interesting. The present study has demonstrated that time domain variables, i. e SDNN, rMSSD and pNN50, increase post WBV; suggesting that this nonconventional exercise modality improves HRV (see Table 2). Moreover, WBV does not require extensive physical activity on the part of the participant. This makes WBV potentially beneficial to the elderly population, who cannot be subjected to extensive effort, and are at high risk of developing cardiovascular diseases. Further studies on WBV using different frequencies and training schedules may improve its applicability in clinics. Financial support None. Conflict of interest statement There were no funding or financial or benefits to the authors. This paper has not been presented in the past in any form. No conflicts of interest have been reported by the authors or by any individuals in control of the content of this article. Acknowledgments We would like to thank all subjects for participating in this study.
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Please cite this article in press as: Licurci, M.d.G.B., et al., Acute effects of whole body vibration on heart rate variability in elderly people, Journal of Bodywork & Movement Therapies (2017), https://doi.org/10.1016/j.jbmt.2017.10.004