535669 research-article2014
WJNXXX10.1177/0193945914535669Western Journal of Nursing ResearchChang
Article
Qigong Effects on Heart Rate Variability and Peripheral Vasomotor Responses
Western Journal of Nursing Research 1–21 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/0193945914535669 wjn.sagepub.com
Mei-Ying Chang1
Abstract Population aging is occurring worldwide, and preventing cardiovascular event in older people is a unique challenge. The aim of this study was to examine the effects of a 12-week qigong (eight-form moving meditation) training program on the heart rate variability and peripheral vasomotor response of middle-aged and elderly people in the community. This was a quasiexperimental study that included the pre-test, post-test, and nonequivalent control group designs. Seventy-seven participants (experimental group = 47; control group = 30) were recruited. The experimental group performed 30 min of eight-form moving meditation 3 times per week for 12 weeks, and the control group continued their normal daily activities. After 12 weeks, the interaction effects indicated that compared with the control group, the experimental group exhibited significantly improved heart rate variability and peripheral vasomotor responses. Keywords qigong, heart rate variability, peripheral vasomotor responses, cold-induced vasodilatation, sympathetic nervous system
1National
Taipei University of Nursing and Health Sciences, Taipei City, Taiwan (R.O.C)
Corresponding Author: Mei-Ying Chang, Graduate Institute of Integration of Traditional Chinese Medicine With Western Nursing, College of Nursing, National Taipei University of Nursing and Health Sciences, No. 365, Ming-te Road, Peitou District, Taipei City, 112, Taiwan (R.O.C). Email: [email protected]
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The worldwide population is rapidly aging, and preventing cardiovascular events in older people is a unique challenge (Klieman, Hyde, & Berra, 2006). Cardiovascular disease is a group of disorders that affect the heart and/or the blood vessels (arteries, capillaries, and veins; Dwivedi, Tripathi, Shukla, Khan, & Chauhan, 2011). In Taiwan, heart disease and cardiovascular diseases are the second and third leading causes of death (Ministry of Health and Welfare, 2013). Generally, aging is associated with changes in cardiac autonomic control as measured by analyzing heart rate variability (Moodithaya & Avadhany, 2012). Furthermore, a reduced heart rate variability has prognostic significance for individuals with cardiovascular disease (Albinet, Boucard, Bouquet, & Audiffren, 2010; Routledge, Campbell, McFetridge-Durdle, & Bacon, 2010). For analyzing heart rate variability parameters, the relationship between the standard deviations of the normal beat-to-beat (R wave to R wave) intervals (SDNN) and total power is interpreted as an indicator of autonomic nervous system activity and regulatory capacity, whereas the high-frequency power is related to vagal activity, and the low frequency power is thought to reflect sympathetic nervous system activity with a parasympathetic nervous system constituent (Routledge et al., 2010). Although the physiological underpinnings of the low frequency/high frequency ratio are controversial (Ashare et al., 2012), the low frequency/high frequency ratio has gained wide acceptance as a parameter to assess cardiovascular autonomic regulation. Specifically, increases in the low frequency/high frequency ratio are assumed to reflect a shift to sympathetic dominance, whereas decreases in the parameters correspond to a shift to parasympathetic dominance (Billman, 2013). Recent study results have consistently indicated that people who are physically active and exercise regularly have higher heart rate variability parameters than people who are sedentary and do not exercise (Golbidi & Laher, 2012; Lu & Kuo, 2006; Pizzinato et al., 2012). However, scant reports exist in the literature concerning the effects of practicing qigong on heart rate variability, particularly in longitudinal studies (Lu & Kuo, 2012). Another hallmark of human aging is the degradation of the peripheral vasomotor responses, which plays a critical role in the pathophysiology of heart disease and the various risks of peripheral vascular disease (Charkoudian, 2010). Generally, peripheral vasomotor responses can be altered in several ways, such as cold-induced vasodilation, higher exercise intensity, and external heating (Castellani & O’Brien, 2005). In general, humans exhibit peripheral vasoconstriction on cold exposure to help retard heat loss and maintain the core temperature, and cold-induced vasodilation is a centrally originating phenomenon caused by sympathetic vasoconstrictor withdrawal (Flouris & Cheung, 2009). When the fingers are immersed in cold water, the sudden fall of the skin temperature is followed by its gradual Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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rise because of cold-induced vasodilation. Typically, cold-induced vasodilation in the finger tips occurs 5 to 10 min after cold exposure of the extremities, which corresponds to an increase in tissue temperature (Daanen, 2003). It is notable that vasodilatation occurs significantly later in older people (Castellani et al., 2006), and the reactivity of fingers to rapidly rewarm following cold exposure is possibly a critical indicator of cold injury protection (Brändström et al., 2008). Therefore, it is believed that cold-induced vasodilation response plays a substantial role in reducing the risk of local cold injuries (Castellani et al., 2006). Physical exercise has been suggested as a potential factor that could affect cold-induced vasodilation response. The average finger skin temperature increased significantly, possibly because of central and/or peripheral cardiovascular and neural adaptations caused by exercise training (Keramidas, Musizza, Kounalakis, & Mekjavic, 2010). Although, qigong practice could improve the function of the circulatory system, coordination, and muscle strength (M. Y. Chang, Yeh, Chu, Wu, & Huang, 2013; S. Lin, 2007), the effects of qigong must be verified in peripheral vasomotor responses. Overall, heart rate variability parameters and peripheral vasomotor responses are markedly reduced in elderly people (K. V. Chang et al., 2011; Yukishita et al., 2010). Previous studies have suggested various exercises as potential factors that could affect heart rate variability (Routledge et al., 2010; Shen & Wen, 2013) and cold-induced vasodilation responses (Dobnikar, Kounalakis, & Mekjavic, 2010; Keramidas et al., 2010). However, a majority of those exercises required higher levels of physical fitness, and were too difficult to learn and practice for many middle-aged and elderly people. Eightform moving meditation is a type of qigong exercise which is a set of easy-to-learn and graceful exercises that can be practiced almost anywhere and at any time (M. Y. Chang et al., 2013). Therefore, we designed a longterm and low-impact qigong training program to explore the effects of an eight-form moving meditation program on the parameters of heart rate variability and peripheral vasomotor responses in middle-aged and elderly people. We hypothesized that participants in the eight-form moving meditation group would demonstrate (a) increased SDNN, total power, low-frequency, and high-frequency values; (b) effective maintenance of the low frequency/high frequency ratio; and (c) improved cold-induced vasodilation responses.
Method Design A time series (two-group pre-test–post-test) quasi-experimental design was used, and potential participants who met the study criteria were informed of Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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the research purposes, intervention benefits and risks, procedures, and the instruments that would be used. Furthermore, the participants were assured that their identities and measurement data would remain confidential, and the participants were informed of their right to withdraw from the study at any time. Before the study was conducted, it was approved by Institutional Review Board of the National Taipei University of Nursing and Health Sciences. A signed consent form was also obtained from all participants.
Sample A nonprobability sampling method was used in this study, and we recruited potential participants during a community meeting. Criteria for the inclusion of participants in the study included having clear consciousness (defined as being awake and responsive to their environment as well as no signs or symptoms of memory problems or dementia), the ability to walk, no neuromuscular diseases, and the ability to communicate in Chinese or Taiwanese. The exclusion criteria included cardiac arrhythmias, any type of thyroid dysfunction, peripheral circulation disease, and other diseases that are known to affect heart rate variability and the thermoregulatory center. Furthermore, other diseases, such as severe arthritis or mental illness, that might impede their participation were excluded. The G-Power was used to estimate the required sample size, and the sample size calculation included heart rate variability as the key outcome and the effect size determined in a previous study on a similar topic (Suresh & Chandrashekara, 2012). Therefore, we estimated the large effect size (d) to be 0.75 (Sandercock, Bromley, & Brodie, 2005) and, based on the parameters of alpha = 0.05 (two-sided) and power value = 0.8, calculated a priori sample size of 29 people per group. Furthermore, we estimated a 30% dropout rate and, therefore, the calculated sample size was 48 people per group. Group assignment was determined based on whether the participants were able to attend a 12-week eight-form moving meditation program session. However, 1 participant (2.1%) from the experimental group dropped out because of hospitalization. In the control group, 16 participants (33.3%) had no motivation to complete the follow-up measurements, and 2 participants (4.2%) dropped out because of influenza. The final sample comprised 47 experimental group participants and 30 control group participants. To accommodate the unequal sample size, the sample size was adjusted according to the allocation ratio of N2/N1 = 1.57, which yielded a statistical power of 0.89. Figure 1 shows the study allocation and follow-up scheme.
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Figure 1. Consort flowchart of this study.
Intervention Eight-form moving meditation was developed by Master Sheng Yen of Dharma Drum Mountain. Eight-form moving meditation incorporates the fundamentals of Chen-style T’ai Chi Ch’uan into a series of simple physical exercises. Eight-form moving meditation guides trainers’ meditation practice
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Starting PostureǺ
First FormǺWaist rotation with swinging arms
Second FormǺNeck Exercise
Third FormǺHip rotation
Fourth FormǺBack stretching and bending
Fifth FormǺSwing and bend
Sixth FormǺUpper body rotations
Seventh FormǺKnee exercise
Eighth sideways
FormǺStretching
Figure 2. Dharma Drum’s eight-form moving meditation. Source. Dharma Drum Retreat Center (2013).
by using clear and detailed steps: relax the mind, bring the mind to the body during movement exercise, and become aware of the breathing process. The forms of eight-form moving meditation include waist rotation with arm swinging, neck exercises, hip rotation, back stretching and bending, swinging and bending, upper-body rotations, knee exercises, and stretching sideways (M. Y. Chang et al., 2013; Dharma Drum Mountain Buddhist Foundation, 2004). Figure 2 shows the forms of eight-form moving meditation. In this study, the intervention was led and monitored by a qualified instructor with 5 years of eight-form moving meditation teaching experience. The participants in the experimental group performed eight-form moving meditation 3 times a week for 12 weeks, and each session conducted at home by the participants themselves lasted 30 min; exercise diaries were used to record data concerning the eight-form moving meditation sessions. To support the engagement of the participants in a home-based exercise program, the researcher could be contacted by telephone if the participants in
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the experimental group had any inquiries or questions about eight-form moving meditation practice. The control group participants continued their routine daily activities and did not participate in any new exercise programs.
Measurements All measurements for the participants in both groups were conducted at baseline and after a 12-week intervention in a soundproof university laboratory maintained at 24°C. In addition, participants were asked not to consume caffeine, tea, or alcoholic beverages for 24 hr, and were instructed to rest quietly for 30 min before heart rate variability and modified cold-induced vasodilation measurements were taken. Heart rate variability measurement. A heart rate variability analyzer (BFM5000 Plus) was used to examine the parameters of heart rate variability (SDNN, total power, high frequency, low frequency, and the low frequency/ high frequency ratio), and the spectral analysis method was used for shortterm (5 min) recordings of R–R intervals under physiologically stable conditions (Chenier-Hogan, Brown, Hains, & Parlow, 2012). The heart rate variability assessment was based on the standard criteria of the Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology (Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, 1996). The following parameters were used to assess the reactivity of heart rate variability in milliseconds (ms): The standard deviation of all SDNNs were used as an overall measure of heart rate variability; the frequency range of the total power was defined as 0.003 to 0.4 Hz, the low-frequency component as 0.04 to 0.15 Hz, and the high-frequency component as 0.15 to 0.4 Hz. Furthermore, the low frequency/high frequency ratio ranged from 1.0 to 2.0 in various groups of healthy volunteers, and a rest period led to no changes or a decrease in the low frequency/high frequency ratio (a range of 0 to 0.5; Pizzinato et al., 2012). The participants were instructed to refrain from performing heavy exercise for at least 1 hr and from consuming coffee, tea, or other caffeinated beverages within a 24-hr period prior to the measurement of heart rate variability. Modified cold-induced vasodilation measurement. Based on the results of previous studies (Buccelletti et al., 2009; Sawada, 2005a, 2005b), we proposed a simplified and less painful modified cold-induced vasodilation test that could be used to gauge peripheral vasomotor responses. The reactivity to the modified cold-induced vasodilation was measured based on the following five Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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parameters: the finger skin temperature before the cold water immersion, the start point of finger skin temperature after the 10-min cold water immersion (S-FST), and the mean and recovery rate of finger skin temperature (M-FST and R-FST) were measured on four separate occasions after the cold water immersion (5, 10, 15, and 20 min). Finally, the differences of finger skin temperature (D-FST) between the S-FST and maximum finger skin temperature after the end of cold water immersion were also calculated. During the measurement period, the participants had a wire thermocouple attached to a middle finger, using thin tape. Participants then immersed one hand that connects thermocouple wire in a tub of cold water (12°C) for 10 min; thus, the modified cold-induced vasodilation parameters were collected.
Statistical Analysis Statistical analysis was conducted using SPSS for Windows version 20 (SPSS, Inc., Chicago, IL, USA). The data were summarized as the mean and standard deviation for continuous variables and as frequencies and percentages for categorical variables. The t-test and the χ2 test were used to analyze group differences. Furthermore, the generalized estimating equation approach was also used because it has become a crucial method for the analysis of longitudinal data obtained from participants that were measured at different points in time. The advantage of generalized estimating equation over the maximum likelihood approach was that it was suitable for the analysis of continuous and discrete outcome variables without the necessity of distribution assumptions toward the response variables (Oh, Carriere, & Park, 2008). In applying generalized estimating equation analysis, imputation methods were not necessary for handling missing data (Twisk & de Vente, 2012) because the standard generalized estimating equation approach avoids the problem of missing data by simply basing inferences on the observed responses, with correlations estimated using “all-available-pairs” (Lipsitz et al., 2009).
Results Characteristics of the Sample A total of 77 subjects were recruited into either the experimental (n = 47, aged 62.98 ± 6.41 years) or the control group (n = 30, aged 65.07 ± 7.38 years). The control group included 11 men and 19 women. On the other hand, the experimental group contained more women (n = 41) than men (n = 6). No statistically significant differences were observed between the experimental group and the control group regarding age and regular exercise habits, but Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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Chang Table 1. Demographic Characteristics of the Participants (N = 77). Variables Gender Male Female Regular exercise Yes No
Experimental (n = 47) n (%)
Control (n = 30) n (%)
6 (12.8) 41 (87.2)
11 (36.7) 19 (63.3)
30 (63.8) 17 (36.2)
21 (70.0) 9 (30.0)
χ2
p
6.080
.023 .628
0.312
significant difference based on gender was observed between the groups (Table 1). At baseline, no significant differences in heart rate variability and modified cold-induced vasodilation parameters were observed between the experimental and control groups (Table 2).
Analysis of the Effect of Eight-Form Moving Meditation Program on Heart Rate Variability Parameters The SDNN, total power, low-frequency, and high-frequency values were significantly higher in the post-test than in the pre-test for the experimental group (Table 2). However, the mean values of SDNN, total power, low frequency, and high frequency for the experimental group increased from 26.98, 618.86, 152.40, and 107.03 points to 32.39, 828.95, 232.08, and 157.07 points after the 12-week follow-up, respectively (Table 2). Furthermore, the generalized estimating equation was used to evaluate the differences after controlling for the potential effect of gender, the interaction effects (group difference and time) showed that the participants in the experimental group achieved a significant increase in SDNN, total power, low-frequency, and high-frequency values at the 12-week follow-up whereas the control group participants did not (β = 8.90, p < .001; β = 464.51, p = .003; β = 176.83, p = .005; and β = 67.65, p = .042, respectively; Table 3). However, no change in the low frequency/high frequency ratio was observed in the experimental group and the control group.
Analysis of the Effect of Eight-Form Moving Meditation Program on Modified Cold-Induced Vasodilation Parameters No statistically significant differences were observed between the two groups regarding the finger skin temperature before the cold water immersion. Although the S-FST of the experimental group was lower than that of the Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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Table 2. Comparisons of the Experimental Group and the Control Group in Heart Rate Variability and Modified Cold-Induced Vasodilation (N = 77).
Variables
Experimental Group (n = 47), Mean (SD)
SDNN (ms) Pre-test 26.98 (11.38) Post-test 32.39 (13.04) Total power (ms2) Pre-test 618.86 (633.13) Post-test 828.95 (867.96) Low frequency (ms2) Pre-test 152.40 (245.73) Post-test 232.08 (315.35) High frequency (ms2) Pre-test 107.03 (120.98) Post-test 157.07 (184.26) Low frequency/high frequency ratio Pre-test 1.73 (1.48) Post-test 1.93 (1.43) B-FST (°C) Pre-test 31.14 (2.21) Post-test 31.64 (1.96) S-FST (°C) Pre-test 16.88 (1.66) Post-test 16.71 (2.51) D-FST (°C) Pre-test 12.66 (3.51) Post-test 14.47 (3.54) M-FST (5 min; °C) Pre-test 21.33 (4.37) Post-test 23.44 (4.50) M-FST (10 min; °C) Pre-test 25.11 (4.44) Post-test 27.09 (4.94) M-FST (15 min; °C) Pre-test 27.55 (4.41) Post-test 29.21 (4.21) M-FST (20 min; °C) Pre-test 29.50 (3.75) Post-test 31.05 (3.49)
Control Group (n = 30), Mean (SD)
t
p
29.25 (11.22) 25.77 (7.67)
−0.858 2.804
.393 .006
769.88 (715.05) 515.46 (402.27)
−0.970 1.852
.335 .068
204.22 (321.90) 105.33 (97.75)
−0.799 2.132
.427 .036
115.75 (102.00) 97.11 (72.18)
−0.327 2.003
.744 .049
1.70 (1.52) 1.34 (1.10)
0.097 1.945
.923 .056
31.54 (2.16) 31.46 (2.61)
−0.771 0.329
.443 .743
17.08 (2.89) 17.69 (2.37)
−0.335 −1.698
.739 .094
13.71 (3.54) 11.36 (4.47)
−1.250 3.195
.215 .002
22.56 (4.84) 21.88 (4.75)
−1.132 1.436
.261 .155
26.56 (4.91) 25.48 (4.89)
−1.319 1.393
.192 .168
28.23 (4.53) 27.21 (5.20)
−0.640 1.839
.524 .070
30.91 (3.62) 28.92 (5.32)
−1.597 1.936
.115 .059 (continued)
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Variables R-FST (5 min; %) Pre-test Post-test R-FST (10 min; %) Pre-test Post-test R-FST (15 min; %) Pre-test Post-test R-FST (20 min; %) Pre-test Post-test
Experimental Group (n = 47), Mean (SD)
Control Group (n = 30), Mean (SD)
t
p
68.57 (12.16) 73.85 (12.03)
71.39 (12.62) 69.34 (12.35)
−0.946 1.585
.347 .117
80.77 (12.59) 85.29 (13.21)
84.05 (13.39) 80.61 (11.60)
−1.087 1.588
.280 .117
88.62 (13.07) 92.06 (10.97)
89.42 (12.39) 86.01 (12.01)
−0.266 2.275
.791 .026
94.99 (11.18) 98.04 (9.42)
97.43 (10.86) 91.47 (12.69)
−0.944 2.438
.348 .018
Note. SDNN = standard deviations of the normal beat-to-beat (R–R) intervals; ms = millisecond; B-FST = finger skin temperature before the cold water immersion; S-FST = start point of finger skin temperature after the 10-min cold water immersion; D-FST = differences of finger skin temperature between the start point of finger skin temperature after the 10-min cold water immersion and maximum finger skin temperature after the end of cold water immersion; M-FST = mean of finger skin temperature after the cold water immersion; R-FST = recovery rate of finger skin temperature after the cold water immersion.
control group, no significant difference was observed between the two groups (Table 2). Furthermore, M-FST was recorded at 5, 10, 15, and 20 min after the end of cold water immersion, and the M-FSTs in the experimental group increased from 21.33, 25.11, 27.55, and 29.50 points in the pre-test to 23.44, 27.09, 29.21, and 31.05 points, respectively, after 12 weeks (Table 2). Compared with the control group, the interaction effects showed that the M-FST of experimental group in the post-test was significantly increased (β = 2.80, p = .026; β = 3.07, p = .014; β = 2.69, p = .030; and β = 3.54, p = .003, respectively; Table 4). Furthermore, the R-FSTs in the experimental group also increased from 68.57, 80.77, 88.62, and 94.99 points in the pre-test to 73.85, 85.29, 92.06, and 98.04 points, respectively, after the 12-week program (Table 2). After controlling for the gender factor, the interaction effects showed that the R-FST of participants in the experimental group increased at the 12-week follow-up (β = 7.31, p = .040; β = 7.95, p = .015; β = 6.86, p = .035; and β = 9.01, p = .005; Table 4). In addition, the amplitudes of coldinduced vasodilation and D-FST values were significantly higher in the experimental group than in the control group (β = 4.18, p = .001). Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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Table 3. Generalized Estimating Equation Analysis of the Effect of Eight-Form Moving Meditation Program on Heart Rate Variability Parameters (N = 77). β
Parameter SDNN (ms) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c Total power (ms2) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c Low frequency (ms2) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c High frequency (ms2) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c Low frequency/high frequency ratio Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c
SE
p
27.87 −2.46 −3.46 0.84 8.90
6.18 2.98 1.97 3.66 2.39
.000 .410 .079 .820 .000
753.45 −151.53 −254.03 9.32 464.51
400.34 191.45 137.98 243.07 154.21
.060 .429 .066 .969 .003
264.73 −50.66 −97.63 −34.63 176.83
147.15 74.38 60.36 82.22 63.21
.072 .496 .106 .674 .005
103.63 −8.89 −18.71 7.06 67.65
61.08 30.71 20.71 36.14 33.32
.090 .772 .366 .845 .042
2.39 0.13 −0.38 −0.41 0.56
0.55 0.36 0.33 0.29 0.40
.000 .725 .253 .155 .170
Note. SDNN = standard deviations of the normal beat-to-beat (R–R) intervals; ms = millisecond; EFMM = eight-form moving meditation. a. Reference group: control group. b. Reference group: time (pre-test). c. Reference group: group (control) × time (pre-test).
Discussion After 12 weeks of eight-form moving meditation training, the participants in the experimental group achieved significantly higher values of SDNN, low Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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Table 4. Generalized Estimating Equation Analysis of the Effect of Eight-Form Moving Meditation Program on Modified Cold-Induced Vasodilation Parameters (N = 77). Parameter D-FST Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c M-FST (5 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c M-FST (10 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c M-FST (15 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c M-FST (20 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c R-FST (5 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c
β
SE
p
15.30 −0.82 −2.33 −0.99 4.18
0.65 0.83 1.03 0.71 1.27
.000 .331 .024 .166 .001
23.54 −1.11 −0.68 −0.60 2.80
2.53 1.12 1.04 1.34 1.26
.000 .323 .514 .655 .026
37.11 −1.38 −1.08 −0.33 3.07
2.28 1.16 1.01 1.25 1.25
.000 .232 .283 .790 .014
28.95 −0.59 −1.03 −0.44 2.69
1.96 1.06 1.01 1.06 1.24
.000 .579 .311 .678 .030
31.42 −1.34 −1.99 −0.31 3.54
1.41 0.90 1.00 0.85 1.20
.000 .135 .048 .712 .003
73.98 −2.48 −2.03 −1.58 7.31
0.03 0.04 0.04 3.80 0.05
.000 .424 .503 .678 .040 (continued)
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Table 4. (continued) Parameter R-FST (10 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c R-FST (15 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c R-FST (20 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c
β
SE
p
85.5 −3.09 −3.42 −0.91 7.95
6.58 3.29 2.70 3.74 3.28
.000 .349 .206 .808 .015
91.32 −0.56 −3.41 −1.15 6.86
5.41 3.10 2.65 3.04 3.25
.000 .856 .197 .704 .035
97.69 −2.40 −5.96 −0.16 9.01
3.82 2.76 2.68 2.40 3.21
.000 .384 .026 .947 .005
Note. D-FST = differences of finger skin temperature between the start point of finger skin temperature after the 10-min cold water immersion and maximum finger skin temperature after the end of cold water immersion; EFMM = eight-form moving meditation; M-FST = mean of finger skin temperature after the cold water immersion; R-FST = recovery rate of finger skin temperature after the cold water immersion. a. Reference group: control group. b. Reference group: time (pre-test). c. Reference group: group (control) × time (pre-test).
frequency, high frequency, and total power than the control group did, and the low frequency/high frequency ratio was the only variable that showed non-significant interaction effects. Typically, the relationship between SDNN and total power are interpreted as an indicator of autonomic nervous activity (Pizzinato et al., 2012). Results from the meta-analysis and other studies indicated that a depressed SDNN is associated with a higher risk of cardiovascular disease and mortality (Buccelletti et al., 2009). Previous researchers have also indicated that qigong regulated the autonomic nervous system by adjusting parasympathetic nervous system activities or stabilizing the sympathetic nervous system, specifically by improving heart rate variability (Lee et al., 2003). As mentioned in the literature review, our findings suggest that practicing the simplified eight-form moving meditation exercises
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might be beneficial in reducing the risk of factors associated with cardiovascular disease in middle-aged and elderly people. Another crucial finding is that eight-form moving meditation practitioners achieved a significantly greater increase in both their low-frequency and high-frequency values at the 12-week follow-up than did the control group. These results differ from certain published studies that have observed that qi therapy increases the high-frequency power and decreases the low-frequency power (Kuan, Chen, & Wang, 2012; Lee, Jang, & Moon, 2004). Certain researchers have observed no differences between experimental groups and control groups regarding all heart rate variability parameters after 12 weeks of qigong training (Kuan et al., 2012). By contrast, Lu and Kuo observed that the heart rate variability parameters (total power, low frequency, and the low frequency/high frequency ratio of T’ai Chi Ch’uan practitioners) were all significantly higher than those of non-practitioners in a cross-sectional analysis; however, the number of years of T’ai Chi Ch’uan experience did not correlate with the value of heart rate variability parameters (Lu & Kuo, 2003). Although generated by complex interactions of sympathetic and parasympathetic functions, most current studies have reported that increasing age is associated with a reduction of low-frequency and high-frequency values (Moodithaya & Avadhany, 2012). Low frequency is jointly contributed by sympathetic and parasympathetic nerves (Routledge et al., 2010); therefore, low frequency might be the key heart rate variability measurement in predicting the aging process of the autonomic nervous system. In previous studies, low frequency has also been observed to be superior as a predictor of mortality. Thus, the combined analysis of the sympathetic and vagal functions of low frequency was revealed to be more accurate in the prediction of mortality and aging (Kuo et al., 1999; Moodithaya & Avadhany, 2012). Furthermore, previous investigators have also shown that qigong regulated the autonomic nervous system by adjusting parasympathetic nervous system activities or stabilizing the sympathetic nervous system, specifically by improving heart rate variability (Chow & Tsang, 2007). Therefore, it seems that practicing eight-form moving meditation can regulate the parasympathetic nervous system and stabilize the sympathetic nervous system. However, we suggest that more consistency is required in how heart rate variability values are used for analyses in studies, and this would allow a more significant discrimination in the relationship between heart rate variability and qigong or other exercises. Furthermore, this study showed that no changes in the low frequency/ high frequency ratio were observed in the eight-form moving meditation group and the control group. This result is consistent with other studies that have also indicated that low frequency/high frequency ratio showed no significantly changes after 3 months of qigong training (Kuan et al., 2012).
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Nevertheless, certain studies have indicated that qi therapy decreased the low frequency/high frequency ratio (Lee et al., 2002; Lee et al., 2004; Lee, Kim, & Lee, 2005). Generally, the low frequency/high frequency ratio has gained wide acceptance as a parameter to assess cardiovascular autonomic regulation, and has been used to quantify the changing relationship between sympathetic and parasympathetic nerve activities (Moodithaya & Avadhany, 2012), but Billman (2013) indicated that the low frequency/high frequency ratio does not accurately measure cardiac sympatho-vagal balance. However, it should be noted that the various exercise training types, durations, and intensities could explain certain of these discrepancies. For instance, programs that are too short, programs lacking in intensity, and resistance and strength training programs seem to have no impact on heart rate variability (Albinet et al., 2010). Therefore, the mechanisms must be verified in future studies. For modified cold-induced vasodilation parameters, no statistically significant differences were observed between the eight-form moving meditation group and the control group for the finger skin temperature before the cold water immersion (31.64 and 31.46, respectively). Although the S-FST of the experimental group (16.71) dropped more than the S-FST of the control group (17.69) did, no significant difference was observed between the two groups. Generally, when the finger was immersed in cold water, a rapid fall of the skin temperature was observed (Daanen, 2003). These findings support the notion that cold exposure induces fluctuations of peripheral vasomotor tone and local skin temperature (Castellani et al., 2006). Furthermore, the D-FST, M-FST, and R-FST values in the eight-form moving meditation group were significantly higher than those in the control group (Table 4). Physical fitness, aerobic training, and endurance exercises have been suggested as the potential factors that could affect cold-induced vasodilation response and increase peripheral blood flow (Castellani & O’Brien, 2005; Keramidas et al., 2010). Reviewing the literature, however, provided no additional details regarding the effects of long-term qigong exercise on cold-induced vasodilation after cold water immersion. Cold-induced vasodilation response is a centrally regulated mechanism based on the suppression and activation of the sympathetic vasoconstrictor system (Flouris & Cheung, 2009). Thus, the cold-induced vasodilation reactivity is suggested for evaluating the sympathetic skin vasomotor function and a peripheral sensory nerve disturbance (Sawada, 2005a). Moreover, coldinduced vasodilation occurs significantly later in older people (Sawada, 2005b). Thus, cold-induced vasodilation response is believed to play a protective role against peripheral cold damage (Dampney et al., 2002; O’Brien, 2005). That is, the extremities of people with excellent cold-induced vasodilation responses are well-protected against cold injuries (Daanen, 2003). In Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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the present study, the modified cold-induced vasodilation parameters (M-FST, R-FST, and D-FST) were thought to reflect the peripheral vasomotor responses on the local cold water stimulus. Therefore, our findings are closely connected with the aforementioned fact that eight-form moving meditation could be an effective method to regulate local skin temperature and prevent peripheral cold injury in middle-aged and elderly people. In addition, the results were extremely encouraging because no participants complained of cold pain or distress during the cold water immersion. Therefore, the modified cold-induced vasodilation test seems to be a practical and effective method for evaluating the reactivity of peripheral vasomotor responses in middle-aged and elderly people. Although the eight-form moving meditation group exhibited significantly improved heart rate variability and peripheral vasomotor responses, the sample sizes were considered minimal based on the established statistical power and effect size, and a nonprobability sampling technique was used. Therefore, the results of this research should be interpreted with caution and cannot be generalized to the entire population of Taiwan. Furthermore, a rigorously designed study with a larger sample size is warranted in the future. We also recommend that further longitudinal experimental studies be conducted for reexamining the effects of eight-form moving meditation training on heart rate variability and peripheral vasomotor responses. In conclusion, this study provides new evidence that the low-impact and simplified qigong eight-form moving meditation (12 weeks) is a valuable contribution to prevent cardiovascular disease and peripheral vascular disease for middle-aged and elderly people. However, the present experiment should be considered as an initial study, and future research should explore the mechanisms on the heart rate variability parameters and modified coldinduced vasodilation responses. Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding The author(s) disclosed the receipt of the following financial support for the research, authorship, and/or publication of this article: This project was supported by funding from the Ministry of Education, Republic of China (Taiwan).
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WJNXXX10.1177/0193945914535669Western Journal of Nursing ResearchChang
Article
Qigong Effects on Heart Rate Variability and Peripheral Vasomotor Responses
Western Journal of Nursing Research 1–21 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/0193945914535669 wjn.sagepub.com
Mei-Ying Chang1
Abstract Population aging is occurring worldwide, and preventing cardiovascular event in older people is a unique challenge. The aim of this study was to examine the effects of a 12-week qigong (eight-form moving meditation) training program on the heart rate variability and peripheral vasomotor response of middle-aged and elderly people in the community. This was a quasiexperimental study that included the pre-test, post-test, and nonequivalent control group designs. Seventy-seven participants (experimental group = 47; control group = 30) were recruited. The experimental group performed 30 min of eight-form moving meditation 3 times per week for 12 weeks, and the control group continued their normal daily activities. After 12 weeks, the interaction effects indicated that compared with the control group, the experimental group exhibited significantly improved heart rate variability and peripheral vasomotor responses. Keywords qigong, heart rate variability, peripheral vasomotor responses, cold-induced vasodilatation, sympathetic nervous system
1National
Taipei University of Nursing and Health Sciences, Taipei City, Taiwan (R.O.C)
Corresponding Author: Mei-Ying Chang, Graduate Institute of Integration of Traditional Chinese Medicine With Western Nursing, College of Nursing, National Taipei University of Nursing and Health Sciences, No. 365, Ming-te Road, Peitou District, Taipei City, 112, Taiwan (R.O.C). Email: [email protected]
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The worldwide population is rapidly aging, and preventing cardiovascular events in older people is a unique challenge (Klieman, Hyde, & Berra, 2006). Cardiovascular disease is a group of disorders that affect the heart and/or the blood vessels (arteries, capillaries, and veins; Dwivedi, Tripathi, Shukla, Khan, & Chauhan, 2011). In Taiwan, heart disease and cardiovascular diseases are the second and third leading causes of death (Ministry of Health and Welfare, 2013). Generally, aging is associated with changes in cardiac autonomic control as measured by analyzing heart rate variability (Moodithaya & Avadhany, 2012). Furthermore, a reduced heart rate variability has prognostic significance for individuals with cardiovascular disease (Albinet, Boucard, Bouquet, & Audiffren, 2010; Routledge, Campbell, McFetridge-Durdle, & Bacon, 2010). For analyzing heart rate variability parameters, the relationship between the standard deviations of the normal beat-to-beat (R wave to R wave) intervals (SDNN) and total power is interpreted as an indicator of autonomic nervous system activity and regulatory capacity, whereas the high-frequency power is related to vagal activity, and the low frequency power is thought to reflect sympathetic nervous system activity with a parasympathetic nervous system constituent (Routledge et al., 2010). Although the physiological underpinnings of the low frequency/high frequency ratio are controversial (Ashare et al., 2012), the low frequency/high frequency ratio has gained wide acceptance as a parameter to assess cardiovascular autonomic regulation. Specifically, increases in the low frequency/high frequency ratio are assumed to reflect a shift to sympathetic dominance, whereas decreases in the parameters correspond to a shift to parasympathetic dominance (Billman, 2013). Recent study results have consistently indicated that people who are physically active and exercise regularly have higher heart rate variability parameters than people who are sedentary and do not exercise (Golbidi & Laher, 2012; Lu & Kuo, 2006; Pizzinato et al., 2012). However, scant reports exist in the literature concerning the effects of practicing qigong on heart rate variability, particularly in longitudinal studies (Lu & Kuo, 2012). Another hallmark of human aging is the degradation of the peripheral vasomotor responses, which plays a critical role in the pathophysiology of heart disease and the various risks of peripheral vascular disease (Charkoudian, 2010). Generally, peripheral vasomotor responses can be altered in several ways, such as cold-induced vasodilation, higher exercise intensity, and external heating (Castellani & O’Brien, 2005). In general, humans exhibit peripheral vasoconstriction on cold exposure to help retard heat loss and maintain the core temperature, and cold-induced vasodilation is a centrally originating phenomenon caused by sympathetic vasoconstrictor withdrawal (Flouris & Cheung, 2009). When the fingers are immersed in cold water, the sudden fall of the skin temperature is followed by its gradual Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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rise because of cold-induced vasodilation. Typically, cold-induced vasodilation in the finger tips occurs 5 to 10 min after cold exposure of the extremities, which corresponds to an increase in tissue temperature (Daanen, 2003). It is notable that vasodilatation occurs significantly later in older people (Castellani et al., 2006), and the reactivity of fingers to rapidly rewarm following cold exposure is possibly a critical indicator of cold injury protection (Brändström et al., 2008). Therefore, it is believed that cold-induced vasodilation response plays a substantial role in reducing the risk of local cold injuries (Castellani et al., 2006). Physical exercise has been suggested as a potential factor that could affect cold-induced vasodilation response. The average finger skin temperature increased significantly, possibly because of central and/or peripheral cardiovascular and neural adaptations caused by exercise training (Keramidas, Musizza, Kounalakis, & Mekjavic, 2010). Although, qigong practice could improve the function of the circulatory system, coordination, and muscle strength (M. Y. Chang, Yeh, Chu, Wu, & Huang, 2013; S. Lin, 2007), the effects of qigong must be verified in peripheral vasomotor responses. Overall, heart rate variability parameters and peripheral vasomotor responses are markedly reduced in elderly people (K. V. Chang et al., 2011; Yukishita et al., 2010). Previous studies have suggested various exercises as potential factors that could affect heart rate variability (Routledge et al., 2010; Shen & Wen, 2013) and cold-induced vasodilation responses (Dobnikar, Kounalakis, & Mekjavic, 2010; Keramidas et al., 2010). However, a majority of those exercises required higher levels of physical fitness, and were too difficult to learn and practice for many middle-aged and elderly people. Eightform moving meditation is a type of qigong exercise which is a set of easy-to-learn and graceful exercises that can be practiced almost anywhere and at any time (M. Y. Chang et al., 2013). Therefore, we designed a longterm and low-impact qigong training program to explore the effects of an eight-form moving meditation program on the parameters of heart rate variability and peripheral vasomotor responses in middle-aged and elderly people. We hypothesized that participants in the eight-form moving meditation group would demonstrate (a) increased SDNN, total power, low-frequency, and high-frequency values; (b) effective maintenance of the low frequency/high frequency ratio; and (c) improved cold-induced vasodilation responses.
Method Design A time series (two-group pre-test–post-test) quasi-experimental design was used, and potential participants who met the study criteria were informed of Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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the research purposes, intervention benefits and risks, procedures, and the instruments that would be used. Furthermore, the participants were assured that their identities and measurement data would remain confidential, and the participants were informed of their right to withdraw from the study at any time. Before the study was conducted, it was approved by Institutional Review Board of the National Taipei University of Nursing and Health Sciences. A signed consent form was also obtained from all participants.
Sample A nonprobability sampling method was used in this study, and we recruited potential participants during a community meeting. Criteria for the inclusion of participants in the study included having clear consciousness (defined as being awake and responsive to their environment as well as no signs or symptoms of memory problems or dementia), the ability to walk, no neuromuscular diseases, and the ability to communicate in Chinese or Taiwanese. The exclusion criteria included cardiac arrhythmias, any type of thyroid dysfunction, peripheral circulation disease, and other diseases that are known to affect heart rate variability and the thermoregulatory center. Furthermore, other diseases, such as severe arthritis or mental illness, that might impede their participation were excluded. The G-Power was used to estimate the required sample size, and the sample size calculation included heart rate variability as the key outcome and the effect size determined in a previous study on a similar topic (Suresh & Chandrashekara, 2012). Therefore, we estimated the large effect size (d) to be 0.75 (Sandercock, Bromley, & Brodie, 2005) and, based on the parameters of alpha = 0.05 (two-sided) and power value = 0.8, calculated a priori sample size of 29 people per group. Furthermore, we estimated a 30% dropout rate and, therefore, the calculated sample size was 48 people per group. Group assignment was determined based on whether the participants were able to attend a 12-week eight-form moving meditation program session. However, 1 participant (2.1%) from the experimental group dropped out because of hospitalization. In the control group, 16 participants (33.3%) had no motivation to complete the follow-up measurements, and 2 participants (4.2%) dropped out because of influenza. The final sample comprised 47 experimental group participants and 30 control group participants. To accommodate the unequal sample size, the sample size was adjusted according to the allocation ratio of N2/N1 = 1.57, which yielded a statistical power of 0.89. Figure 1 shows the study allocation and follow-up scheme.
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Figure 1. Consort flowchart of this study.
Intervention Eight-form moving meditation was developed by Master Sheng Yen of Dharma Drum Mountain. Eight-form moving meditation incorporates the fundamentals of Chen-style T’ai Chi Ch’uan into a series of simple physical exercises. Eight-form moving meditation guides trainers’ meditation practice
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Starting PostureǺ
First FormǺWaist rotation with swinging arms
Second FormǺNeck Exercise
Third FormǺHip rotation
Fourth FormǺBack stretching and bending
Fifth FormǺSwing and bend
Sixth FormǺUpper body rotations
Seventh FormǺKnee exercise
Eighth sideways
FormǺStretching
Figure 2. Dharma Drum’s eight-form moving meditation. Source. Dharma Drum Retreat Center (2013).
by using clear and detailed steps: relax the mind, bring the mind to the body during movement exercise, and become aware of the breathing process. The forms of eight-form moving meditation include waist rotation with arm swinging, neck exercises, hip rotation, back stretching and bending, swinging and bending, upper-body rotations, knee exercises, and stretching sideways (M. Y. Chang et al., 2013; Dharma Drum Mountain Buddhist Foundation, 2004). Figure 2 shows the forms of eight-form moving meditation. In this study, the intervention was led and monitored by a qualified instructor with 5 years of eight-form moving meditation teaching experience. The participants in the experimental group performed eight-form moving meditation 3 times a week for 12 weeks, and each session conducted at home by the participants themselves lasted 30 min; exercise diaries were used to record data concerning the eight-form moving meditation sessions. To support the engagement of the participants in a home-based exercise program, the researcher could be contacted by telephone if the participants in
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the experimental group had any inquiries or questions about eight-form moving meditation practice. The control group participants continued their routine daily activities and did not participate in any new exercise programs.
Measurements All measurements for the participants in both groups were conducted at baseline and after a 12-week intervention in a soundproof university laboratory maintained at 24°C. In addition, participants were asked not to consume caffeine, tea, or alcoholic beverages for 24 hr, and were instructed to rest quietly for 30 min before heart rate variability and modified cold-induced vasodilation measurements were taken. Heart rate variability measurement. A heart rate variability analyzer (BFM5000 Plus) was used to examine the parameters of heart rate variability (SDNN, total power, high frequency, low frequency, and the low frequency/ high frequency ratio), and the spectral analysis method was used for shortterm (5 min) recordings of R–R intervals under physiologically stable conditions (Chenier-Hogan, Brown, Hains, & Parlow, 2012). The heart rate variability assessment was based on the standard criteria of the Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology (Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, 1996). The following parameters were used to assess the reactivity of heart rate variability in milliseconds (ms): The standard deviation of all SDNNs were used as an overall measure of heart rate variability; the frequency range of the total power was defined as 0.003 to 0.4 Hz, the low-frequency component as 0.04 to 0.15 Hz, and the high-frequency component as 0.15 to 0.4 Hz. Furthermore, the low frequency/high frequency ratio ranged from 1.0 to 2.0 in various groups of healthy volunteers, and a rest period led to no changes or a decrease in the low frequency/high frequency ratio (a range of 0 to 0.5; Pizzinato et al., 2012). The participants were instructed to refrain from performing heavy exercise for at least 1 hr and from consuming coffee, tea, or other caffeinated beverages within a 24-hr period prior to the measurement of heart rate variability. Modified cold-induced vasodilation measurement. Based on the results of previous studies (Buccelletti et al., 2009; Sawada, 2005a, 2005b), we proposed a simplified and less painful modified cold-induced vasodilation test that could be used to gauge peripheral vasomotor responses. The reactivity to the modified cold-induced vasodilation was measured based on the following five Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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parameters: the finger skin temperature before the cold water immersion, the start point of finger skin temperature after the 10-min cold water immersion (S-FST), and the mean and recovery rate of finger skin temperature (M-FST and R-FST) were measured on four separate occasions after the cold water immersion (5, 10, 15, and 20 min). Finally, the differences of finger skin temperature (D-FST) between the S-FST and maximum finger skin temperature after the end of cold water immersion were also calculated. During the measurement period, the participants had a wire thermocouple attached to a middle finger, using thin tape. Participants then immersed one hand that connects thermocouple wire in a tub of cold water (12°C) for 10 min; thus, the modified cold-induced vasodilation parameters were collected.
Statistical Analysis Statistical analysis was conducted using SPSS for Windows version 20 (SPSS, Inc., Chicago, IL, USA). The data were summarized as the mean and standard deviation for continuous variables and as frequencies and percentages for categorical variables. The t-test and the χ2 test were used to analyze group differences. Furthermore, the generalized estimating equation approach was also used because it has become a crucial method for the analysis of longitudinal data obtained from participants that were measured at different points in time. The advantage of generalized estimating equation over the maximum likelihood approach was that it was suitable for the analysis of continuous and discrete outcome variables without the necessity of distribution assumptions toward the response variables (Oh, Carriere, & Park, 2008). In applying generalized estimating equation analysis, imputation methods were not necessary for handling missing data (Twisk & de Vente, 2012) because the standard generalized estimating equation approach avoids the problem of missing data by simply basing inferences on the observed responses, with correlations estimated using “all-available-pairs” (Lipsitz et al., 2009).
Results Characteristics of the Sample A total of 77 subjects were recruited into either the experimental (n = 47, aged 62.98 ± 6.41 years) or the control group (n = 30, aged 65.07 ± 7.38 years). The control group included 11 men and 19 women. On the other hand, the experimental group contained more women (n = 41) than men (n = 6). No statistically significant differences were observed between the experimental group and the control group regarding age and regular exercise habits, but Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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Experimental (n = 47) n (%)
Control (n = 30) n (%)
6 (12.8) 41 (87.2)
11 (36.7) 19 (63.3)
30 (63.8) 17 (36.2)
21 (70.0) 9 (30.0)
χ2
p
6.080
.023 .628
0.312
significant difference based on gender was observed between the groups (Table 1). At baseline, no significant differences in heart rate variability and modified cold-induced vasodilation parameters were observed between the experimental and control groups (Table 2).
Analysis of the Effect of Eight-Form Moving Meditation Program on Heart Rate Variability Parameters The SDNN, total power, low-frequency, and high-frequency values were significantly higher in the post-test than in the pre-test for the experimental group (Table 2). However, the mean values of SDNN, total power, low frequency, and high frequency for the experimental group increased from 26.98, 618.86, 152.40, and 107.03 points to 32.39, 828.95, 232.08, and 157.07 points after the 12-week follow-up, respectively (Table 2). Furthermore, the generalized estimating equation was used to evaluate the differences after controlling for the potential effect of gender, the interaction effects (group difference and time) showed that the participants in the experimental group achieved a significant increase in SDNN, total power, low-frequency, and high-frequency values at the 12-week follow-up whereas the control group participants did not (β = 8.90, p < .001; β = 464.51, p = .003; β = 176.83, p = .005; and β = 67.65, p = .042, respectively; Table 3). However, no change in the low frequency/high frequency ratio was observed in the experimental group and the control group.
Analysis of the Effect of Eight-Form Moving Meditation Program on Modified Cold-Induced Vasodilation Parameters No statistically significant differences were observed between the two groups regarding the finger skin temperature before the cold water immersion. Although the S-FST of the experimental group was lower than that of the Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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Table 2. Comparisons of the Experimental Group and the Control Group in Heart Rate Variability and Modified Cold-Induced Vasodilation (N = 77).
Variables
Experimental Group (n = 47), Mean (SD)
SDNN (ms) Pre-test 26.98 (11.38) Post-test 32.39 (13.04) Total power (ms2) Pre-test 618.86 (633.13) Post-test 828.95 (867.96) Low frequency (ms2) Pre-test 152.40 (245.73) Post-test 232.08 (315.35) High frequency (ms2) Pre-test 107.03 (120.98) Post-test 157.07 (184.26) Low frequency/high frequency ratio Pre-test 1.73 (1.48) Post-test 1.93 (1.43) B-FST (°C) Pre-test 31.14 (2.21) Post-test 31.64 (1.96) S-FST (°C) Pre-test 16.88 (1.66) Post-test 16.71 (2.51) D-FST (°C) Pre-test 12.66 (3.51) Post-test 14.47 (3.54) M-FST (5 min; °C) Pre-test 21.33 (4.37) Post-test 23.44 (4.50) M-FST (10 min; °C) Pre-test 25.11 (4.44) Post-test 27.09 (4.94) M-FST (15 min; °C) Pre-test 27.55 (4.41) Post-test 29.21 (4.21) M-FST (20 min; °C) Pre-test 29.50 (3.75) Post-test 31.05 (3.49)
Control Group (n = 30), Mean (SD)
t
p
29.25 (11.22) 25.77 (7.67)
−0.858 2.804
.393 .006
769.88 (715.05) 515.46 (402.27)
−0.970 1.852
.335 .068
204.22 (321.90) 105.33 (97.75)
−0.799 2.132
.427 .036
115.75 (102.00) 97.11 (72.18)
−0.327 2.003
.744 .049
1.70 (1.52) 1.34 (1.10)
0.097 1.945
.923 .056
31.54 (2.16) 31.46 (2.61)
−0.771 0.329
.443 .743
17.08 (2.89) 17.69 (2.37)
−0.335 −1.698
.739 .094
13.71 (3.54) 11.36 (4.47)
−1.250 3.195
.215 .002
22.56 (4.84) 21.88 (4.75)
−1.132 1.436
.261 .155
26.56 (4.91) 25.48 (4.89)
−1.319 1.393
.192 .168
28.23 (4.53) 27.21 (5.20)
−0.640 1.839
.524 .070
30.91 (3.62) 28.92 (5.32)
−1.597 1.936
.115 .059 (continued)
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Variables R-FST (5 min; %) Pre-test Post-test R-FST (10 min; %) Pre-test Post-test R-FST (15 min; %) Pre-test Post-test R-FST (20 min; %) Pre-test Post-test
Experimental Group (n = 47), Mean (SD)
Control Group (n = 30), Mean (SD)
t
p
68.57 (12.16) 73.85 (12.03)
71.39 (12.62) 69.34 (12.35)
−0.946 1.585
.347 .117
80.77 (12.59) 85.29 (13.21)
84.05 (13.39) 80.61 (11.60)
−1.087 1.588
.280 .117
88.62 (13.07) 92.06 (10.97)
89.42 (12.39) 86.01 (12.01)
−0.266 2.275
.791 .026
94.99 (11.18) 98.04 (9.42)
97.43 (10.86) 91.47 (12.69)
−0.944 2.438
.348 .018
Note. SDNN = standard deviations of the normal beat-to-beat (R–R) intervals; ms = millisecond; B-FST = finger skin temperature before the cold water immersion; S-FST = start point of finger skin temperature after the 10-min cold water immersion; D-FST = differences of finger skin temperature between the start point of finger skin temperature after the 10-min cold water immersion and maximum finger skin temperature after the end of cold water immersion; M-FST = mean of finger skin temperature after the cold water immersion; R-FST = recovery rate of finger skin temperature after the cold water immersion.
control group, no significant difference was observed between the two groups (Table 2). Furthermore, M-FST was recorded at 5, 10, 15, and 20 min after the end of cold water immersion, and the M-FSTs in the experimental group increased from 21.33, 25.11, 27.55, and 29.50 points in the pre-test to 23.44, 27.09, 29.21, and 31.05 points, respectively, after 12 weeks (Table 2). Compared with the control group, the interaction effects showed that the M-FST of experimental group in the post-test was significantly increased (β = 2.80, p = .026; β = 3.07, p = .014; β = 2.69, p = .030; and β = 3.54, p = .003, respectively; Table 4). Furthermore, the R-FSTs in the experimental group also increased from 68.57, 80.77, 88.62, and 94.99 points in the pre-test to 73.85, 85.29, 92.06, and 98.04 points, respectively, after the 12-week program (Table 2). After controlling for the gender factor, the interaction effects showed that the R-FST of participants in the experimental group increased at the 12-week follow-up (β = 7.31, p = .040; β = 7.95, p = .015; β = 6.86, p = .035; and β = 9.01, p = .005; Table 4). In addition, the amplitudes of coldinduced vasodilation and D-FST values were significantly higher in the experimental group than in the control group (β = 4.18, p = .001). Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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Table 3. Generalized Estimating Equation Analysis of the Effect of Eight-Form Moving Meditation Program on Heart Rate Variability Parameters (N = 77). β
Parameter SDNN (ms) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c Total power (ms2) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c Low frequency (ms2) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c High frequency (ms2) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c Low frequency/high frequency ratio Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c
SE
p
27.87 −2.46 −3.46 0.84 8.90
6.18 2.98 1.97 3.66 2.39
.000 .410 .079 .820 .000
753.45 −151.53 −254.03 9.32 464.51
400.34 191.45 137.98 243.07 154.21
.060 .429 .066 .969 .003
264.73 −50.66 −97.63 −34.63 176.83
147.15 74.38 60.36 82.22 63.21
.072 .496 .106 .674 .005
103.63 −8.89 −18.71 7.06 67.65
61.08 30.71 20.71 36.14 33.32
.090 .772 .366 .845 .042
2.39 0.13 −0.38 −0.41 0.56
0.55 0.36 0.33 0.29 0.40
.000 .725 .253 .155 .170
Note. SDNN = standard deviations of the normal beat-to-beat (R–R) intervals; ms = millisecond; EFMM = eight-form moving meditation. a. Reference group: control group. b. Reference group: time (pre-test). c. Reference group: group (control) × time (pre-test).
Discussion After 12 weeks of eight-form moving meditation training, the participants in the experimental group achieved significantly higher values of SDNN, low Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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Table 4. Generalized Estimating Equation Analysis of the Effect of Eight-Form Moving Meditation Program on Modified Cold-Induced Vasodilation Parameters (N = 77). Parameter D-FST Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c M-FST (5 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c M-FST (10 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c M-FST (15 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c M-FST (20 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c R-FST (5 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c
β
SE
p
15.30 −0.82 −2.33 −0.99 4.18
0.65 0.83 1.03 0.71 1.27
.000 .331 .024 .166 .001
23.54 −1.11 −0.68 −0.60 2.80
2.53 1.12 1.04 1.34 1.26
.000 .323 .514 .655 .026
37.11 −1.38 −1.08 −0.33 3.07
2.28 1.16 1.01 1.25 1.25
.000 .232 .283 .790 .014
28.95 −0.59 −1.03 −0.44 2.69
1.96 1.06 1.01 1.06 1.24
.000 .579 .311 .678 .030
31.42 −1.34 −1.99 −0.31 3.54
1.41 0.90 1.00 0.85 1.20
.000 .135 .048 .712 .003
73.98 −2.48 −2.03 −1.58 7.31
0.03 0.04 0.04 3.80 0.05
.000 .424 .503 .678 .040 (continued)
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Table 4. (continued) Parameter R-FST (10 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c R-FST (15 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c R-FST (20 min) Intercept Group (EFMM)a Time (post-test)b Gender Group (EFMM) × Time (post-test)c
β
SE
p
85.5 −3.09 −3.42 −0.91 7.95
6.58 3.29 2.70 3.74 3.28
.000 .349 .206 .808 .015
91.32 −0.56 −3.41 −1.15 6.86
5.41 3.10 2.65 3.04 3.25
.000 .856 .197 .704 .035
97.69 −2.40 −5.96 −0.16 9.01
3.82 2.76 2.68 2.40 3.21
.000 .384 .026 .947 .005
Note. D-FST = differences of finger skin temperature between the start point of finger skin temperature after the 10-min cold water immersion and maximum finger skin temperature after the end of cold water immersion; EFMM = eight-form moving meditation; M-FST = mean of finger skin temperature after the cold water immersion; R-FST = recovery rate of finger skin temperature after the cold water immersion. a. Reference group: control group. b. Reference group: time (pre-test). c. Reference group: group (control) × time (pre-test).
frequency, high frequency, and total power than the control group did, and the low frequency/high frequency ratio was the only variable that showed non-significant interaction effects. Typically, the relationship between SDNN and total power are interpreted as an indicator of autonomic nervous activity (Pizzinato et al., 2012). Results from the meta-analysis and other studies indicated that a depressed SDNN is associated with a higher risk of cardiovascular disease and mortality (Buccelletti et al., 2009). Previous researchers have also indicated that qigong regulated the autonomic nervous system by adjusting parasympathetic nervous system activities or stabilizing the sympathetic nervous system, specifically by improving heart rate variability (Lee et al., 2003). As mentioned in the literature review, our findings suggest that practicing the simplified eight-form moving meditation exercises
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might be beneficial in reducing the risk of factors associated with cardiovascular disease in middle-aged and elderly people. Another crucial finding is that eight-form moving meditation practitioners achieved a significantly greater increase in both their low-frequency and high-frequency values at the 12-week follow-up than did the control group. These results differ from certain published studies that have observed that qi therapy increases the high-frequency power and decreases the low-frequency power (Kuan, Chen, & Wang, 2012; Lee, Jang, & Moon, 2004). Certain researchers have observed no differences between experimental groups and control groups regarding all heart rate variability parameters after 12 weeks of qigong training (Kuan et al., 2012). By contrast, Lu and Kuo observed that the heart rate variability parameters (total power, low frequency, and the low frequency/high frequency ratio of T’ai Chi Ch’uan practitioners) were all significantly higher than those of non-practitioners in a cross-sectional analysis; however, the number of years of T’ai Chi Ch’uan experience did not correlate with the value of heart rate variability parameters (Lu & Kuo, 2003). Although generated by complex interactions of sympathetic and parasympathetic functions, most current studies have reported that increasing age is associated with a reduction of low-frequency and high-frequency values (Moodithaya & Avadhany, 2012). Low frequency is jointly contributed by sympathetic and parasympathetic nerves (Routledge et al., 2010); therefore, low frequency might be the key heart rate variability measurement in predicting the aging process of the autonomic nervous system. In previous studies, low frequency has also been observed to be superior as a predictor of mortality. Thus, the combined analysis of the sympathetic and vagal functions of low frequency was revealed to be more accurate in the prediction of mortality and aging (Kuo et al., 1999; Moodithaya & Avadhany, 2012). Furthermore, previous investigators have also shown that qigong regulated the autonomic nervous system by adjusting parasympathetic nervous system activities or stabilizing the sympathetic nervous system, specifically by improving heart rate variability (Chow & Tsang, 2007). Therefore, it seems that practicing eight-form moving meditation can regulate the parasympathetic nervous system and stabilize the sympathetic nervous system. However, we suggest that more consistency is required in how heart rate variability values are used for analyses in studies, and this would allow a more significant discrimination in the relationship between heart rate variability and qigong or other exercises. Furthermore, this study showed that no changes in the low frequency/ high frequency ratio were observed in the eight-form moving meditation group and the control group. This result is consistent with other studies that have also indicated that low frequency/high frequency ratio showed no significantly changes after 3 months of qigong training (Kuan et al., 2012).
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Nevertheless, certain studies have indicated that qi therapy decreased the low frequency/high frequency ratio (Lee et al., 2002; Lee et al., 2004; Lee, Kim, & Lee, 2005). Generally, the low frequency/high frequency ratio has gained wide acceptance as a parameter to assess cardiovascular autonomic regulation, and has been used to quantify the changing relationship between sympathetic and parasympathetic nerve activities (Moodithaya & Avadhany, 2012), but Billman (2013) indicated that the low frequency/high frequency ratio does not accurately measure cardiac sympatho-vagal balance. However, it should be noted that the various exercise training types, durations, and intensities could explain certain of these discrepancies. For instance, programs that are too short, programs lacking in intensity, and resistance and strength training programs seem to have no impact on heart rate variability (Albinet et al., 2010). Therefore, the mechanisms must be verified in future studies. For modified cold-induced vasodilation parameters, no statistically significant differences were observed between the eight-form moving meditation group and the control group for the finger skin temperature before the cold water immersion (31.64 and 31.46, respectively). Although the S-FST of the experimental group (16.71) dropped more than the S-FST of the control group (17.69) did, no significant difference was observed between the two groups. Generally, when the finger was immersed in cold water, a rapid fall of the skin temperature was observed (Daanen, 2003). These findings support the notion that cold exposure induces fluctuations of peripheral vasomotor tone and local skin temperature (Castellani et al., 2006). Furthermore, the D-FST, M-FST, and R-FST values in the eight-form moving meditation group were significantly higher than those in the control group (Table 4). Physical fitness, aerobic training, and endurance exercises have been suggested as the potential factors that could affect cold-induced vasodilation response and increase peripheral blood flow (Castellani & O’Brien, 2005; Keramidas et al., 2010). Reviewing the literature, however, provided no additional details regarding the effects of long-term qigong exercise on cold-induced vasodilation after cold water immersion. Cold-induced vasodilation response is a centrally regulated mechanism based on the suppression and activation of the sympathetic vasoconstrictor system (Flouris & Cheung, 2009). Thus, the cold-induced vasodilation reactivity is suggested for evaluating the sympathetic skin vasomotor function and a peripheral sensory nerve disturbance (Sawada, 2005a). Moreover, coldinduced vasodilation occurs significantly later in older people (Sawada, 2005b). Thus, cold-induced vasodilation response is believed to play a protective role against peripheral cold damage (Dampney et al., 2002; O’Brien, 2005). That is, the extremities of people with excellent cold-induced vasodilation responses are well-protected against cold injuries (Daanen, 2003). In Downloaded from wjn.sagepub.com at UNIV OF PENNSYLVANIA on August 28, 2015
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the present study, the modified cold-induced vasodilation parameters (M-FST, R-FST, and D-FST) were thought to reflect the peripheral vasomotor responses on the local cold water stimulus. Therefore, our findings are closely connected with the aforementioned fact that eight-form moving meditation could be an effective method to regulate local skin temperature and prevent peripheral cold injury in middle-aged and elderly people. In addition, the results were extremely encouraging because no participants complained of cold pain or distress during the cold water immersion. Therefore, the modified cold-induced vasodilation test seems to be a practical and effective method for evaluating the reactivity of peripheral vasomotor responses in middle-aged and elderly people. Although the eight-form moving meditation group exhibited significantly improved heart rate variability and peripheral vasomotor responses, the sample sizes were considered minimal based on the established statistical power and effect size, and a nonprobability sampling technique was used. Therefore, the results of this research should be interpreted with caution and cannot be generalized to the entire population of Taiwan. Furthermore, a rigorously designed study with a larger sample size is warranted in the future. We also recommend that further longitudinal experimental studies be conducted for reexamining the effects of eight-form moving meditation training on heart rate variability and peripheral vasomotor responses. In conclusion, this study provides new evidence that the low-impact and simplified qigong eight-form moving meditation (12 weeks) is a valuable contribution to prevent cardiovascular disease and peripheral vascular disease for middle-aged and elderly people. However, the present experiment should be considered as an initial study, and future research should explore the mechanisms on the heart rate variability parameters and modified coldinduced vasodilation responses. Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding The author(s) disclosed the receipt of the following financial support for the research, authorship, and/or publication of this article: This project was supported by funding from the Ministry of Education, Republic of China (Taiwan).
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