Among the old and middle-aged people, the advancing age, cardiovascular diseases, or mental load (e.g. long-term exposure to a tense and high-load work environment or pressure) will cause increased sympathetic activity, decreased pneumogastric activity, and decreased heart rate variability (HRV)[1]. Researches have shown that long-term participation in aerobics can increase the tension of the pneumogastric nerves of the old and middle-aged people. Increased tension of pneumogastric nerves will elevate the threshold of ventricular fibrillation and thus protect the heart[2]. In order to observe the effects of Health Qigong•Yi Jin Jing on the functions of the autonomic nervous system, our research group conducted HRV tests on the experimental group and control group in the 10th month of the experiment.

5.2.1 Objects and methodology

5.2.1.1 Objects

Old students from University for the Aged People of Jiangxi Province and Activity Center for Retired Cadres of the Provincial Party Committee of Jiangxi are selected in this research as the experimental objects. These objects are aged between 50 and 70 and do not have any history of systematic physical exercises or severe diseases. 64 female objects are selected from the experimental and control groups. 37 of them belong to the experimental group (aged 62.76±6.18 on an average) and 27 the control group (aged 63.74±5.15 on an average). By t-test (t=0.67, P＞0.05) there is no significant difference between both groups in terms of age.

5.2.1.2 Methodology

Objects of the experimental group practice Health Qigong•Yi Jin Jing for 1h every morning for at east 5 days a week. Instructors are assigned to coach and instruct these objects. Official versions released by Health Qigong Administration Center of General Administration of Sports of China are used as the basis for the routines, requirements, and teaching guidance of Health Qigong•Yi Jin Jing[3]. The control group does not participate in Health Qigong exercise or any other systematic fitness activity.

Test instruments and analysis system: Electrocardiorecorder (supplied by No.4 Research Institute of PLA Air Force); dedicated analysis software (supplied by Scientific and Technological Research Department of Health Qigong Administration Center, General Administration of Sports of China); “Shenfeng” disposable electrocardio-electrode (manufactured by Shanghai Shenfeng Medical and Health Supplies Co., Ltd).

(1) Standard load test

Preparation: Stick test electrocardio-electrodes to the sternal angle (negative electrode), xiphoid process (reference electrode), and the intersection between the lower edge of the left hypochondrial region and the anterior axillary line. Use conducting wires to connect the electrodes to the electrocardiorecorder. Put the electrocardiorecorder in a small custom-made bag and fix the bag at the waist.

Test: The object shall calm down and sit in a relaxed manner and then take the test in the following seven consecutive time periods:

Periods ① and ⑦: Relax and sit quietly in background music for 10min;

Periods ② and ⑥: Stand up and sit down repeatedly for 5min under the guidance of a metronome (20 beats/min);

Periods ③ and ⑤: Relax and sit quietly in background music for 5min;

Period ④: Sit up straight on the chair and follow oral commands to take deep breaths for 5min (12 breaths/min).

(2) Test of practicing process

Preparation: Same as standard load test.

Test: The object calms down and sits in a relaxed manner and then takes the test in the following three consecutive time periods:

Periods ① and ③: Relax and sit quietly in background music for 15min;

Period ②: Practice Health Qigong•Yi Jin Jing once (about 12min) with the music of Health Qigong•Yi Jin Jing.

(3) Data processing

Take out the SM card from the electrocardiorecorder and import data into a computer using a card reader. Use a special-purpose analysis software to pre-treat the data.

Use SPSS10.0 statistic software to analyze and process the data and conduct intra-group and inter-group difference tests of the results of the experimental and control group before and after the experiment.

5.2.2 Results

5.2.2.1 Standard load test

(1) Time domain analysis

① R-R mean comparison between both groups

R-R mean reflects the time interval between two neighboring R waves. The reciprocal of R-R interval is just the real-time heart rate. Since the experimental group has taken a 10-month practice of the exercise by the time of the experiment, the before-experiment R-R mean value of the experimental group is significantly higher than that of the control group, indicating that after a period of exercise, the practicers have significantly slower heart rates than non-practicers. By further observation of the R-R mean values before, during, and after the experiment, we can see that the value of the experimental group varies in a high-low-high pattern, indicating that after the withdrawal of the standard load, the heart rate can quickly return to the normal level. On the other hand the value of the control group varies in a high-low-low pattern, indicating that after the withdrawal of the standard load, the heart rate continues to increase. There is significant difference between the variation patterns of both groups.

Table 5.2-1 Comparison between R-R mean values of both groups (ms， )

GroupBefore experimentDuring experimentAfter experiment

Experimental group n=37821.15±83.89688.67±73.62709.53±83.86

Control group n=27770.71±95.83635.63±68.60619.31±75.85

Note: “Before experiment” means the “sitting quietly” period before the standard load is imposed. “During experiment” means the movement period under the standard load. “After experiment” means the “sitting quietly” period before the standard load is withdrawal. Same as below.

We further analyze Table 1 and use the difference between R-R mean values before and after the experiment and the difference between R-R mean values during and after the experiment to reflect the variation pattern of R-R mean during the standard load test.

From Table 2 we can see that the differences between the values of both groups before and during the experiment are positive, indicating that the heart rate increases as the body turns from the static state to the dynamic state. By comparison between both groups (t=0.184，P＞0.05), there is no significant difference. On the other hand, however, the difference between the values of the experimental group during and after the experiment is negative and the value of the control group is positive, indicating that when the body turns from the dynamic state to the static state, the heart rate of the experimental group quickly returns to the original level while the heart rate of the control group still keeps increasing and the recovery of heart rate is lagged. By comparison between both groups (t=4.20，P＜0.05), there is very significant difference.

Table 5.2-2 Comparison between variation patterns of R-R mean values of both groups (ms， )

DifferenceExperimental group n=37Control group n=27t

Difference between before-experiment value and during-experiment value132.48±49.62135.08±63.610.184

Difference between during-experiment value and after-experiment value-20.86±28.6416.32±42.214.20**

② R-R RMSSD test results of both groups

From Table 3 we can see that the RMSSD value of the experimental group remains relatively stable throughout the experiment without much change, while the value of the control group significantly falls back. The RMSSD values of both groups are not significantly different (P＞0.05) before the experiment, become a little different (P＞0.05) during the experiment, and finally become significantly different after the experiment (P＜0.05).

Table 5.2-3 Comparison between RMSSD values of both groups (ms， )

Experimental processExperimental group n=37Control group n=27t

Before experiment21.93±9.6724.60±18.390.75

During experiment21.30±12.8817.93±8.171.19

After experiment23.34±16.0012.24±6.823.38**

Note: t1 means comparison between before-experiment value and during-experiment value. t2 means comparison between during-experiment value and after-experiment value. t3 means comparison between before-experiment value and after-experiment value. * means P＜0.05, and ** means P＜0.01. (Same as below).

② R-R Coefficient of Variation (CV) test results of both groups

CV is the ratio of standard deviation over mean value. CV values of both groups are not significantly different before, during, and after the experiment, as shown in the table below (P＞0.05). This is probably because the experimental group has been practicing for 10 months by the time of this test. Although the variation of standard deviation of the experimental group is greater than that of the control group, its mean value is correspondingly greater than that of the control group.

Table 5.2-4 Comparison between CV values of both groups ((%， )

Practicing processExperimental group n=37Control group n=27t

Before experiment4.21±1.244.36±2.450.32

During experiment16.04±4.1615.12±3.400.94

After experiment14.46±4.9813.66±4.200.68

(2) Frequency domain analysis

① Normalized low-frequency power test results of both groups

The low-frequency power reflects the intensity of sympathetic neuromodulation. Table 5 shows that the normalized LF power of the control group changes from a low level before the experiment to a high level during the experiment, and then to a slightly higher level after the experiment. The values before, during and after the experiment are all significantly different from each other (P＜0.05). The normalized LF power value significantly increases, indicating that the tension of sympathetic nerves continuously rises, the inhibition by the parasympathetic nerves on the sympathetic nerves is inadequate, and the heart rate keeps increasing. On the other hand, the normalized LF power of the experimental group changes from a low level before the experiment to a high level during the experiment, and then falls back slightly after the experiment. The three groups of data are not significantly different from each other (P＞0.05), indicating that the tension of sympathetic nerves increases not as significantly as that of the control group during the movement under the standard load, and during the recovery period after the movement, the tension of sympathetic nerves of the experimental group is quickly attenuated due to the alternating inhibition by the parasympathetic nerves and the heart rate is hence gradually recovered.

Table 5.2-5 Comparison between normalized LF values of both groups (ms2， )

GroupBefore experimentDuring experimentAfter experimentt1t2t3

Experimental group n=3554.32±19.4861.68±15.7460.64±20.021.790.251.38

Control group n=2755.63±19.7567.18±18.4868.07±22.142.22*0.162.18*

② Normalized high-frequency power test results of both groups

The high-frequency power reflects the intensity of pneumogastric neuromodulation. Table 6 shows that the normalized HF power of the control group changes from a high level before the experiment to a lower level during the experiment, and then to an even lower level after the experiment. The values before, during and after the experiment are all significantly different from each other (P＜0.05). The gradual decrease in the normalized HF power indicates that the tension of pneumogastric nerves is falls due to the alternating inhibition by the increasing tension of the sympathetic nerves and that the heart rate is increased accordingly. And the normalized HF power of the experimental group changes from a high level before the experiment to a slightly lower level during the experiment, and finally rises again after the experiment. The values before, during and after the experiment are not significantly different from each other (P＞0.05). The normalized HF power remains fairly stable on a relatively high level, indicating that the experimental group has a stronger ability to regulate the pneumogastric nerves.

Table 5.2-6 Comparison between normalized HF values of both groups (ms2， )

GroupBefore experimentDuring experimentAfter experimentt1t2t3

Experimental group n=3545.69±19.4838.32±15.7439.36±20.021.790.251.38

Control group n=2744.37±19.7532.83±18.4831.93±22.142.22*0.162.18*

③ HF peak position (HP) test results of both groups

HP is related to the respiratory rhythm. The value of HP is equivalent to the number of breaths per minute. Table 7 shows that the HP value of the control group increases significantly after the experiment and that there are very significant differences between values before, during, and after the experiment (P＜0.01). The significant increase of HP value indicates the sharp acceleration of breath. And the HP value of the experimental group remains relatively stable throughout the experiment, indicating that the breath is stable.

Table 5.2-7 Comparison between HP values of both groups (ms2， )

GroupBefore experimentDuring experimentAfter experimentt1t2t3

Experimental group n=350.263±0.0610.264±0.0630.272±0.0750.070.500.57

Control group n=270.263±0.0660.261±0.0760.314±0.0680.102.70**2.80**

5.2.2.2 Test of practicing process

We conducted a heart rate variability test of the experimental group during the process of Health Qigong•Yi Jin Jing training and observed the dynamic changes in HRV before, during, and after the practice.

(1) Time domain analysis

Table 8 shows that R-R mean changes from a high value before the practice to a lower value during the practice, and finally returns to a high value after the practice and that there are very significant differences between before-practice value and during-practice value and between during-practice value and after-practice value. But there is no significant difference between values before and after the practice. RMSSD value remains stable at a high level and there is no significant difference by comparison. CV value remains increases and then falls back and there are significant differences by comparison.

Table 5.2-8 Results of time domain analysis of HRV test of the practicing process (n=33， )

Test itemBefore practiceDuring practiceAfter practicet1t2t3

R-R mean(ms)835.76±140.00659.29±91.14800.11±1126.07**5.60**1.14

RMSSD(ms2)21.93±13.1918.95±12.8520.12±11.730.930.390.59

CV(%)4.33±1.539.26±2.695.81±1.679.26**6.26**3.75**

It is generally believed that the target heart rate of the old and middle-aged people participating in aerobics shall be 60~80% of the maximum heart rate. Heart rates beyond this range will lead to risks. From Table 8 we can see that R-R mean values before, during, and after the practice are approximately equivalent to heart rates of 72, 91, and 75 (bpm). The average heart rate 91 bpm during the practice can both ensure the exercising effect and provide good safety. And after the practice, the heart rate can quickly return to the level before the practice and RMSSD value remains stable at a high level. Both facts indicate that the practicers have strong regulating ability of the pneumogastric nerves.

(2) Frequency domain analysis

Table 9 shows that the normalized LF value changes from a low level to a high value and finally falls back during the experimental process. The normalized HF value changes from a high level to a low level and finally rise again. And there are very significant differences between before-experiment value and during-experiment value and between during-experiment value and after-experiment value. But there is no significant difference between values before and after the experiment . HP value remains stable at a high level throughout the experiment and there is no significant difference by comparison. The results described above indicate that the excitedness of sympathetic nerves is increased significantly at the beginning of the exercise. Then the tension of pneumogastric nerves are inhibited and deceased as a result. The heart rate is increased but breathing is not significantly increased. However, once the exercise is completed, the pneumogastric nerves immediately take strong regulating effects and the excitedness of the sympathetic nerves is inhibited. As a result the heart rate returns to the normal level in a short time and the breath remains stable.

Table 5.2-9 Results of frequency domain analysis of HRV test of the practicing process (n=34， )

Before practiceDuring practiceAfter practicet1t2t3

Normalized LF55.61±20.1380.35±12.0760.22±16.846.15**5.67**1.02

Normalized HF44.39±20.1319.50±12.0039.77±16.856.19**5.71**1.03

HP0.258±0.0650.224±0.0880.261±0.0711.811.910.18

5.2.3 Discussion

Heart rate variability means the variation degree of sinus heart rate. It is one of the noninvasive electrocardiographic monitoring indicators that have received special attention in recent years. It is generally believed that the cardiac rhythm is directly subject to the dual-regulation by the cardiac sympathetic and cardiac pneumogastric nerves, which also restrict each other. When the sympathetic nervous system is excited, the pneumogastric nervous system will be inhibited and both the heart rate and breath will be accelerated. When the pneumogastric nervous system is excited, the sympathetic nervous system will be inhibited and both the heart rate and breath will be decelerated. The interactions between the sympathetic and pneumogastric nervous systems lead to the irregularity of heart rate variation. Therefore HRV is taken as an important indicator for the evaluation of the autonomic nervous system functions[4]. This research is focused on the study of HRV. Although we failed to record the electrocardiographic data of both groups at the beginning of the entire research (before the experiment), we used standard load experiments to test HRV and to observe changes in the HRV of research objects during a static-dynamic (standard load)-static process. The standard load experiment has the same principles as the electrocardiogram exercise load test (ET) which has been widely applied clinically. During the experiment, the cardiac muscles of the individual will have greater demand for blood and oxygen. In particular the broken compensation of the coronary arteries will cause lack of blood and oxygen for the cardiac muscles in the blood-supplying positions, change the balance of the autonomic neural regulation of the heart, weaken the regulating effect on the heart, and lead to decreased HRV. The condition of the illness will get worse and worse as HRV falls more and more significantly[5][6]. Results of this research shows that HRV values of both groups are significantly different. After the standard-load movement, the R-R mean value of the control group is further decreased but its LF and HP values are increased. During the beginning, middle, and ending stages of the standard-load movement, RMSSD and HF values significantly fall back. This result coincides with the HRV of normal healthy old and middle-aged people[1][2]. From this we can see that after the standard-load movement is over, the sympathetic nervous system of the control group still has a high tension and the pneumogastric nerve cannot take any significant regulating effect in the short run. On the other hand, after the standard-load movement, the R-R mean value of the experiment group quickly returns to the normal level, the LF value quickly falls back , and the heart rate quickly returns to the normal value. RMSSD, HF, and HP values remain stable during the beginning, middle, and ending stages of the standard-load movement, so does the breath. This indicates that the tension of the pneumogastric nervous system of the practicer remains at a high level. The excitedness of the sympathetic nervous system is quickly inhibited by the pneumogastric nerves and gets decreased after the standard-load movement is over. This will improve the electrocardiographic stability, relieve the blood and oxygen shortage of the cardiac muscles, and reduce the chances of diseases such as hypertension and artherosclerosis[7].

Health Qigong•Yi Jin Jing belongs to aerobics and bears the “muscle-stretching, bone-pulling”, “guiding Qi with postures” , “well-stretched movements”, “mind following the posture” “natural breath”, and “gentle and smooth” features. The average heart rate of 91 bpm in the practicing process (reciprocal of R-R mean) is exactly within the range of target heart rates for the old and middle-aged people participating in aerobics. Therefore Health Qigong•Yi Jin Jing belongs to medium-intensity fitness exercises like Taoji Quan and biking[1][8], which are quite suitable for the old and middle-aged. Judging from the results that RMSSD value remains stable at a high level, normalized HF value quickly rises again, and HP value remains unchanged, we can conclude that the tension of pneumogastric nerve of practicers remain at a high level, the regulating effect of autonomic nerves are significantly strengthened, and the physical fitness of practicers is significantly improved after 10 months of Health Qigong•Yi Jin Jing practice.

Due to the small number of samples, some other indicators of HRV have great standard deviates and are therefore not suitable for analysis. Further research with more samples is needed.

References

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[3] Health Qigong Administration Center of General Administration of Sports of China. Health Qigong•Yi Jin Jing [M]. Beijing: People’s Sports Publishing House,2003.

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[8] Sun Xusheng. Effects of Simplified Tai Ji Quan on HRV Indicators [J]. Chinese Journal of Rehabilitation Medicine,1998, (13)5: 225~226.