Growing evidence indicates that psychological stress contributes to cardiovascular diseases through complex neuroendocrine mechanisms. Psychological stress leads to several physiological responses including increased heart rate (HR) and blood pressure (BP) as well as decreased heart rate variability (HRV) through alterations in the autonomic nervous system (ANS), specifically increased sympathetic nervous system (SNS) activity and decreased parasympathetic nervous system (PNS) activity. ^[1] These changes, if persistent, can contribute to the development of a variety of cardiovascular diseases. Approaches to management of psychological stress have been developed with the goal of reducing stress, thus eliminating adverse physiological responses. ^[2]

Meditation is one approach to stress management which, according to current understandings of physiology, may induce a positive parasympathetic state and counteract increased sympathetic activity, thereby reducing HR and BP as well as increasing HRV. The focus of this study was to evaluate the relationships among meditation practice, perceived stress and activity of the ANS as indicated by BP and HRV in meditators. ^[3]

Meditation is more than just sitting in a cross-legged position, eyes closed and hands on either knee with a closed forefinger and thumb. Much occurs internally while in a meditative state, beginning with focusing the mind on the third eye (ajna chakra)--the space between the eyes. Notably, a practitioner can strive to be engaged in meditation throughout all daily activities; truly, this is much more the aim of yoga. ^[4]

Because of the increasing popularity of and devotion to yoga practice in the West, researchers in health-related fields are designing new program theories that utilize yoga in some way. These researchers take constituents (limbs) of yoga (i.e. meditation, postures) and reconfigure them into a new style of practice fitting to the language of the west, so people here can understand the benefits. Typically, these reconfigurations of yoga include holding classes over a period of a number of weeks, where the participant engages in guided yoga postures (asanas) and meditation (dhyana). ^[5]

Psychological stress is viewed by Lazarus and Folkman (1984) as a particular relationship between the person and the environment that is appraised by the person as taxing or exceeding his or her resources and endangering his or her well-being. Viewing psychological stress in this manner, two critical processes, cognitive appraisal and coping, mediate the person-environment relationships. ^[6]

Cognitive appraisal is an evaluative process that determines why and to what extent a particular transaction between the person and the environment is assessed as psychological stress. Coping is the process through which the individual manages the demands that are appraised as stressors. Thus, results of psychological stress without effective coping processes can be physiological and psychological problems. High levels of psychological stress have been associated with minor illnesses like insomnia, backache, or headache, and can contribute to potentially life-threatening diseases such as high BP and heart disease. ^[7]

This is prospective and observational study was conducted in the Department of Physiology, Index Medical College from January 2022 to July 2024.

The aim of this pre & post-yoga interventional study was to evaluate the efficacy of 6 months yoga practice on cardio-respiratory fitness and mental health including perceived stress and memory status and plasma nitric oxide level in healthy individuals.

The effects of 6 months yoga practice on cardio-respiratory fitness and mental health of all the study participants/subjects were evaluated at two times. First, investigations or evaluations were made before the study begins or yoga intervention was given and second, immediately after the completion of yoga intervention period i.e. six months.

All the evaluated variables before the yoga intervention i.e. baseline or pre- intervention were labeled as ‘baseline’ or ‘pre-yogic exercise’ and after the yoga intervention i.e. post-intervention were labeled as ‘post-yogic exercise’.

On the day of evaluation, no yogic exercise was given. Study Protocol: Fig. No.6 shows the study protocol.

Study Subjects:

All the male and female study subjects were healthy individuals and were within the age range of 30 to 50 years with mean age 39.95 years.

INCLUSION AND EXCLUSION CRITERIA

Inclusion Criteria

Subjects who have fulfilled the following criteria were enrolled in the study:

Healthy subjects who were not practicing or practiced either yoga or any other type of exercise and willing to practice only yoga on 1 hr/day basis for 6 months continuously; and

Exclusion Criteria

Any of the following was regarded as a criterion for exclusion from the study:

• Subjects already practicing yoga or any other type of physical exercise;
• Subjects with Cardiovascular diseases (CVDs) and or respiratory diseases;
• Subjects with any systemic diseases; history of cancer;
• Subject with memory impairments, mental or psychiatric disorders; and
• Subjects under any specific medications,

Post Selection Exclusion criteria

Any of the following was regarded as a criterion for exclusion from the study:

• Subjects discontinued the yoga practice or adopted any type of physical exercise with or without yoga;
• Subjects who were not following the study protocol for exercise;
• Subjects who developed any disease mentioned in exclusion criteria during the intervention period;
• Subjects who voluntarily opted to withdraw from the study;

SELECTION OF STUDY SUBJECTS

The study subjects were selected after the screening i.e. general health check-up to qualify for the inclusion. The screening was done by general and systemic clinical examination by the Physician on three consecutive days between 6:00 to 10:00 am for the qualification of subjects for the inclusion in the study.

Day 1: Personal, demographic information and self rated physical fitness was recorded; detailed medical history was taken, the physiological parameters like Arterial Blood Pressure (ABP), Heart Rate (HR) or Pulse Rate (PR), and Peak Expiratory Flow Rate (PEFR) were recorded. Electrocardiograms (ECG) were recorded at rest. As per the Indian Guidelines on Hypertension (I.G.H)-III – 2013⁴⁸ systolic blood pressure (SBP) & diastolic blood pressure (DBP) values (Table No.4) are taken into account for inclusion & exclusion criteria.

Day 2: Arterial Blood Pressure (ABP), Heart Rate (HR), and Peak Expiratory Flow Rate (PEFR) were recorded.

Day 3: Arterial Blood Pressure (ABP), Heart Rate (HR) or Pulse Rate (PR), and Peak Expiratory Flow Rate (PEFR) were recorded.

All the measurement values for various parameters were tested as per inclusion and exclusion criteria and subjects were included in the study, thereafter.

PRE & POST-YOGIC EXERCISE PARAMETER MEASUREMENTS

Pre-Yogic Exercise Parameters:

All the tests, measurements, recordings of study parameters were done before actual commencement of yoga practice/intervention and were designated as ‘Pre- yogic’ parameters. All the tests, measurements, recordings, etc. were performed under the presence and supervision of the Physician, between 06:00 to 10:00 AM. On the day of tests, measurements, recordings, yoga intervention was not given.

• Anthropometric measurements such as height, weight & body mass index (BMI), Basal Metabolic Rate (BMR).
• Cardiac Parameters:           Arterial         Blood         Pressure,          Heart Rate, Electrocardiogram (ECG);
• Respiratory Parameters: Peak Expiratory Flow Rate (PEFR), Forced Expiratory Volume (FEV1), Vital Capacity (VC);
• Physical Fitness      Index      (PFI)      &     Maximum        Oxygen                     Consumption (VO2max);
• Memory Status, Perceived Stress and Mental Health Index along with sub- scale and global scale.
• Total Plasma Nitric Oxide (NOx).

Post-Yogic Exercise Parameters:

All the tests, measurements, recordings of study parameters were done after the completion of yoga intervention i.e. six months and were designated as ‘Post- yogic’ parameters. All the tests, measurements, recordings, etc. were performed under the presence and supervision of the Physician, between 06:00 to 10:00 AM. On the day of tests, measurements, recordings, yoga was not practiced.

• Anthropometric measurements such as height, weight & body mass index (BMI), Basal Metabolic Rate (BMR).
• Arterial Blood Pressure, Heart Rate, Electrocardiogram (ECG);
• Peak Expiratory Flow Rate (PEFR), Forced Expiratory Volume (FEV1), Vital Capacity (VC);
• Physical Fitness      Index      (PFI)      &     Maximum        Oxygen                     Consumption (VO2max);
• Memory Status, Perceived Stress and Mental Health Index along with sub- scale and global scale.
• Total Plasma Nitric Oxide (NOx).

STATISTICAL ANALYSIS

Pre-intervention i.e. pre-yogic and post-intervention i.e. post-yogic data values for all the parameters under the study were collected and compiled in MS- Excel-2007 sheets. The data collected during the entire study was analyzed by using SPSS (29^th Version). The data obtained was expressed in mean and standard deviation (SD). The data collected was represented by using bar and pia diagrams, etc. Paired t-test was applied to determine the significant difference between baseline i.e. pre-yogic and post-yogic data values. The p-value was established at 5% level of significance.

1.     AGE AND GENDER BASED DISTRIBUTION OF STUDY SUBJECT

Interpretation

In the present study, total number healthy study subjects (n) were 200. Out of 200 study subjects, 120 were male (60%) and 80 were female (40%) subjects as shown in Table No.23.Age based distribution of study subjects was shown in Table No.24 & Fig. No.**. Out of 200 study subjects, 52.50% subjects (n=105) were in the age group of 30 – 40 years and 47.50% subjects (n=95) were in 41 – 50 years age group with Mean age = 39.95 years.

EFFECT OF YOGA ON ANTHROPOLOGIC PARAMETERS

Result

Pre-yogic exercise and post-yogic exercise data related to anthropologic parameters- Weight, Body Mass Index (BMI) and Basal Metabolic Rate (BMR) are summarized in Graph No.3.

Interpretation

Weight

We found that, after 6 months of yoga practice there was highly significant (p<0.0001) reduction in mean weight from 69.19 kg to 67.32 kg. The mean weight was reduced by 1.87 Kg after 6 months of yoga practice (Table No.25).

Body Mass Index (BMI)

We found significant reduction (p<0.0001) in Body Mass Index (BMI) after regular yoga practice of yoga for six months. Reduction in BMI was from

25.30 to 24.63 Kg/m² with mean difference 0.67 Kg (Table No.25).

Basal Metabolic Rate (BMR)

Post-yogic exercise mean Basal Metabolic Rate (BMR) was noticed to be significantly increased (p=0.0051) than its pre-yogic exercise value. It was increased from 1490.73 to 1511.18 calories/day with mean BMR 20.44 Calories/day (Table No.25).

EFFECT OF YOGA ON CARDIOVASCULAR PARAMETERS

Result

Baseline or pre-yogic and post-yogic exercise cardiovascular parameters like heart rate (HR), blood pressures – systolic blood pressure (SBP) & diastolic blood pressure (DBP) and ECG changes were measured. The effects of yoga on these parameters are shown in Graph No.5, 6.

Interpretation

Heart Rate

Resting Heart Rate

Baseline or pre-yogic resting heart rate was noted to be 79.97 bpm and after yoga intervention i.e. post-yogic it was noted to be 74.82 bpm. Reduction in post-yogic resting heart than its baseline value by 5.15 bpm was found to be highly significant (p<0.0001) (Table No.26).

Heart Rate after HST:

We found that, baseline (pre-yogic) post-yogic HR after HST was 141.69 bpm and pre-yogic HR after HST was 135.14 bpm. This indicates that; post-yogic heart rate after HST was increased by 6.54 bpm than its baseline value. This increase was found to be statistically highly significant (p<0.0001) (Table No.26).

Blood Pressure

Resting Systolic Blood Pressure (SBP)

Baseline resting SBP was 128.41 mmHg and post-yogic resting SBP was

124.04 mmHg. Result shows that there was highly significant decrease (p<0.0001) in post-yogic resting SBP than pre-yogic resting SBP by 4.36 mmHg units (Table No.26).

Resting Diastolic blood Pressure (DBP)

While analyzing the data we noticed that; pre-yogic resting DBP was79.63 mmHg and post-yogic resting DBP was 78.55 mmHg. Result shows that there was highly significant decrease (p<0.0001) in post yogic DBP than pre-yogic DBP by 1.08 mmHg units (Table No.26).

Systolic Blood Pressure (SBP) after Harvard Step Test (HST)

It was noted that, pre-yogic SBP after HST was higher i.e. 167.65 mmHg than post-yogic SBP after HST i.e. 160.20 mmHg. This reduction in SBP from 167.65 mmHg to 160.20 mmHg with mean difference of 7.45 mmHg after HST was found to be statistically highly

significant (p<0.0001) (Table No.26).

Diastolic Blood Pressure (DBP) after Harvard Step Test (HST)

It was noted that, pre-yogic mean DBP after HST was higher i.e. 83.26 mmHg than post-yogic mean DBP after HST i.e. 81.79 mmHg. This reduced DBP from 83.26 mmHg to 81.79 mmHg with mean difference of 1.47 mmHg after HST was found to be statistically highly significant (p<0.0001) (Table No.26).

Electrocardiogram

Pre-yogic ECG at rest, after HST and post-yogic ECG at rest and after HST was found to be within normal limits.

EFFECT OF YOGA ON TOTAL PLASMA NITRIC OXIDE LEVEL (NOx)

Result

Baseline i.e. pre-yogic and post-yogic total plasma nitric oxide levels were measured and are summarized in Table No.27.

Meditation has a number of positive effects on the physiology of the human body. It has been shown to reduce

the heart rate, blood pressure and thus, the practice of meditation significantly helps in the management and the

prevention of CAD by reducing the risk factors which are associated with the same. In our study, we found that  resting heart rate in the patients practicing meditation for a period of 6 months was decreased significantly as compared to those in the non-meditating subjects. The statistical analysis showed that the differences were

highly significant. In a study which was conducted in 1984 on 25 rajyogis, both males and females, by the  medical wing of Rajyoga Education and Research Foundation, an overall decrease in the mean values of the  heart rate, systolic and diastolic blood pressure was observed. [8]

Meditation is associated with a blunted sympathetic activity as is shown by a reduction in the heart rate after

regular meditation for a period of 6 months. Similar trends in the heart rate were noted in other studies. The  Mean±SD value for systolic blood pressure in the meditators was 130.5±10.2 and in the non-meditators, it was  138.9±9.9. Similarly, the Mean±SD value for diastolic blood pressure in the meditator subjects was 76.4±9.2 and in the non-meditator subjects, it was 84.5±6.8. Statistically, these results were found to be significant. In other studies, there was a significant reduction in the systolic and diastolic blood pressure, serum cholesterol and the incidence of ischaemic heart disease in the meditators. [9]

It was reported that not only in hypertensive individuals, but in normotensive individuals also, the regular practice of meditation could reduce the ambulatory blood pressure levels and hence, it could give significant protection from cardiovascular diseases. [10] Improvements in the cardiovascular parameters in the present study were similar to those which were found in other studies on meditation. The decrease in the diastolic and systolic blood pressure and the heart rate may be because of the activation of the parasympathetic state. [11]

Meditation, by modifying the state of anxiety, reduces the stress induced sympathetic over-activity, resulting in  lowering of the diastolic blood pressure and the heart rate.It makes the person relaxed and thus decreases the arterial tone and the peripheral resistance. [12] This could be another reason for the fall in the diastolic blood  pressure. Environmental conditions and a variety of behavioral factors such as stress, anxiety and the affective  and attitudinal disposition of the individual influences the cardiovascular responses. Meditation affects the hypothalamus and brings about a decrease in the diastolic and systolic blood pressures through its influence on the vasomotor centre, which reduces the sympathetic tone and the peripheral resistance. [13]

Prior studies of meditation and blood pressure have been criticized because of the quality of the trials, potential side effects of meditation, [15] and potential bias of investigators. [14] Different studies stated that the benefits of meditation and relaxation could only be maintained by the regular practice and integration of these techniques in

the day to day life. [15] Also, the amount of the practice of meditation does not correlate with the amount of blood pressure reduction after the training. Regular meditation is required to maintain positive effects on the blood pressure and the heart rate (36) for at least 60 minutes/day. 

In the present study, it was concluded that there is significant decrease in the heart rate and systolic and diastolic blood pressure in CAD patients practicing meditation for a period of 6 months. Our findings are also in compliance with the study conducted by Lang et al. (37) and Wenneberg et al. (38) on the effect of Meditation on heart rate and blood pressure by regulating sympathetic activity. The results of the present study demonstrate that practicing meditation reduces heart rate and blood pressuren in CAD patients and that change were more marked in yoga group. It can be concluded from the present study that meditation helps in improving health status of an individual including heart rate and blood pressure. Furthermore, the practice should be adopted and continued for a long duration.

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