Research in Cardiovascular Medicine

: 2020  |  Volume : 9  |  Issue : 1  |  Page : 16--22

The effect of 8 weeks of combined yoga and rehabilitation training on salivary levels of alpha-amylase and cortisol in patients after coronary artery bypass grafting

Fatemeh Fakharirad1, Farshad Ghazalian1, Hojatollah Nikbakht1, Sara Lotfian2, Akbar Nikpajouh2,  
1 Department of Physical Education and Sport Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran
2 Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran

Correspondence Address:
Dr. Farshad Ghazalian
Department of Physical Education and Sport Sciences, Science and Research Branch, Islamic Azad University, Tehran


Background: The purpose of this study was to investigate the effects of combined rehabilitation and yoga training on salivary levels of alpha-amylase and cortisol in patients after coronary artery bypass graft (CABG). Methods: In this quasi-experimental study, 20 CABG patients were randomly divided into two groups of cardiac rehabilitation training group (CRT, n = 10) and combined training group (yoga-cardiac rehabilitation) (computed tomography [CT], n = 10). After initial clinical evaluation, exercise test, and salivation with 12 h fasting, individuals were referred to the rehabilitation ward of Shahid Rajaie Heart Hospital in Tehran and performed their exercise program for 8 weeks and three sessions per week then their evaluations were made again. A dependent t-test was used for intra-group changes and an independent t-test was used to compare the two groups at a significant level of 0.05. Results: The CT group showed a significant effect on salivary cortisol (P = 0.028), but these interventions did not show a significant effect on salivary alpha-amylase (P = 0.193). Furthermore, CRT alone had a significant effect on salivary cortisol indices (P = 0.011), there was no significant difference between groups (P ≤ 0.05). Conclusion: The results showed that combined yoga and rehabilitation training had beneficial effects on the salivary levels of the stress factors that have been studied. Therefore, this type of rehabilitation exercise is recommended for secondary prevention of cardiovascular disease.

How to cite this article:
Fakharirad F, Ghazalian F, Nikbakht H, Lotfian S, Nikpajouh A. The effect of 8 weeks of combined yoga and rehabilitation training on salivary levels of alpha-amylase and cortisol in patients after coronary artery bypass grafting.Res Cardiovasc Med 2020;9:16-22

How to cite this URL:
Fakharirad F, Ghazalian F, Nikbakht H, Lotfian S, Nikpajouh A. The effect of 8 weeks of combined yoga and rehabilitation training on salivary levels of alpha-amylase and cortisol in patients after coronary artery bypass grafting. Res Cardiovasc Med [serial online] 2020 [cited 2020 Dec 4 ];9:16-22
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The effects and increasing prevalence of cardiovascular disease (CVD) are largely driven by economic changes, social structure, lifestyle, and a parallel increase in life expectancy in the 20th century.[1] Many risk factors for CVD have been identified, including hypertension, hyperlipidemia, hyperglycemia, unhealthy diet, physical inactivity, tobacco use, alcohol abuse, obesity, and mental stress.[2],[3] These behavioral risk factors are responsible for 80% of all cases of coronary artery disease and stroke. In addition, psychological stress has caused undesirable changes in autonomic sound that are important for cardiovascular risks but are modifiable.[4],[5]

Recent studies have displayed that the cardioprotective effects of rehabilitation programs may lead to improved regulation of the autonomic nervous system (ANS). For example, in a study conducted by Malfatto et al.,[6] the short-term effects of exercise were examined in 22 patients after myocardial infarction. The researchers proposed that 8 weeks of exercise training could regulate cardiovascular autonomic function by increasing parasympathetic tone, which is known to be associated with better cardiovascular outcomes.[7]

In a review study by Besnier et al., the effect of exercise training on modulating the ANS was examined. Patients with CVD exhibited autonomic abnormalities, including sympathetic activation and vagal withdrawal, leading to fatal accidents. This article considers sympathetic vagal balance as an essential element in the management of patients with CVD who benefit from a cardiac rehabilitation program. In general, cardiac rehabilitation programs include continuous aerobic exercise and low-intensity exercise. Other forms of activity including high-intensity intermittent exercise, respiratory exercises, relaxation, and electrical stimulation of the skin can improve vagal sympathetic balance and should be included in cardiac rehabilitation programs to optimize individual health outcomes. Overall, the results suggested that exercise training, along with other nonpharmacological strategies, could have a positive effect on the ANS by increasing vagal oscillations and decreasing sympathetic tone.[8]

There is developmental evidence that the hypothalamic- pituitary-adrenal (HPA) axis plays a role in the progression of CVD. The HPA axis is an important component of the neuroendocrine system that controls stress response and some important physical functions. Cortisol is the end product of the HPA axis and it affects the number of factors associated with the causes of CVD.

Few studies have been performed on the effects of changing daily cortisol rhythm on cardiovascular events and mortality in patients with CVD. Therefore, the relationship between daily preoperative cortisol and clinical outcomes in patients undergoing coronary artery bypass graft surgery (CABG) has been investigated. The daily cortisol gradient before surgery appears to be associated with higher rates of future heart events and mortality in the years following CABG.[9]

The HPA and sympathetic nervous system (SNS) systems can be considered as two important stress response factors. One of the two branches of the ANS is the SNS. In recent literature, sex addicts anonymous is often referred to as the SNS activity index, or more precisely the medullary adrenal medullary system (sympatho-adrenomedullary-axis), which is responsible for the release of epinephrine and norepinephrine. According to the results of the study by Nater et al., we conclude that the measurement of salivary alpha-amylase may be an additional useful tool for the measurement of biological stress factors because it is not related to other markers such as catecholamines or cortisol.[10]

Evidence from some research suggests that specific yoga techniques may improve mental and physical health by reducing the regulation of the HPA axis and the SNS. The HPA and SNS axis leads to a cascade of physiological, behavioral, and psychological effects in response to physical or psychological need (stressors), mainly due to the release of cortisol and catecholamines (epinephrine and norepinephrine). This response results in the amount of energy needed to combat stressors through the classic fight-or-flight syndrome.

In a study, Sieverdes et al. found that hatha yoga had beneficial changes in blood pressure and decrease in salivary alpha-amylase, in prehypertensive adolescents.[11] On the other hand, yoga as an anti-stress effect on these pathways and modulating sympathetic pathways and the HPA can be considered as secondary prevention of CVD. Therefore, cardiac rehabilitation exercises have been effective, but traditional rehabilitation is not working for these patients, and many researchers are looking for new ways of rehabilitation which nowadays patients are more inclined to do so and are not as elusive as traditional remedies, according to studies of secondary prevention of these diseases, often of psychological and stress origin.

In general, various studies have been conducted on the effects of yoga and rehabilitation on coronary artery disease patients, and some contradictory results have been obtained as some results indicated a meaningful increase in curing of different factors in the disease the others found that these factors did not change significantly. However, little is known about the interactive effects of these two exercises, and their interactive effect on secondary prevention of CVD and sudden death remains unclear. On the other hand, there has been no research comparing the effects of rehabilitation practice with combined rehabilitation and yoga practice.



The present study is a randomized controlled clinical trial with pretest and posttest design (clinical trial number IRCT20180728040615N1). Since this study was performed in Shahid RajaieHeart Center in Tehran, prior to the beginning of the research process, it was coordinated with the officials of Shahid Rajaie Cardiovascular Center and Rehabilitation Unit of Tehran Heart Surgery Center and then patients who underwent surgeries of CABG in the first 3 months of the year 97 were invited. In order to carry out this research, the Ethics Committee for Biological Research, Faculty of Medical Sciences of Tehran Azad University of Medical Sciences (IR.IAU.SRB.REC.1396.97) was first approved.

Study design

In order to collect the sample from the target community, details of the plan including goals, benefits, and course length were explained for patients first by telephone or in-person with patients referring to the rehabilitation ward of Shahid Rajaie Hospital for consultation to be invited to attend the briefing if they agreed. Initial clinical evaluations (history, previous history of CVD, clinical examinations and diagnostic measures of electrocardiogram (ECG), echocardiography, and exercise testing) were performed by a specialist physician. According to the sports medicine physician's opinion and the inclusion criteria, eventually, 20 patients who were eligible and had no motor inhibition were selected. Inclusion criteria were: patients who had undergone at least 1 month of surgery and were in phase 2 discharge, age ranged from 40 to 75 years, the patient was not a professional athlete and had no exercise program in the past 6 months. He did not participate regularly and did not participate in any other exercise program while smoking. Exclusion criteria were: restrictive exercise conditions (neurological, muscular, and skeletal) during the study, patients with hypertension, ventricular arrhythmia, unstable angina, and aortic valve disease, as well as patients with gastric ulcers and stomach discomfort, generally, heart problems that prohibit physical activity, changing the dosage, type, or discontinuation of the medications used in the study samples or patients taking nerve or sedative medications. They used to eat. Two days before the beginning of the training plan, the individuals were present at the rehabilitation center to take appropriate measures including height and weight measurement, exercise test, oral hygiene, and dental hygiene. Prior to grouping each individual, a modified Bruce standardized test strip was performed. Cardiac response to the test was monitored continuously during the test using a 12-derivative ECG. Blood pressure was also measured manually at the end of each phase of the test. The test continued to the extent of fatigue and voluntary helplessness. Pretest heart rate, pretest, and 1–3 min' recovery after exercise test were measured and recorded in sitting position. On the 2nd day at 8 o'clock in the hospital rehab unit to receive saliva with 12 h fasting and saliva were taken in saliva collection tubes. All tests were performed on patients before and after 8 weeks of the exercise protocol and were statistically analyzed.

Then, in order to match people into two groups (yoga-rehabilitation group and rehabilitation group), patients were randomly divided into two groups through using the information obtained including age, leap rate above 35%, comorbidities, etc., Patients were randomly divided into two groups of rehabilitation (or cardiac rehabilitation training [CRT] [n = 10]) and combined group (yoga-rehabilitation), (or computed tomography [CT] [n = 10]).[12],[13],[14],[15] In order to be blind at this stage, the names of the individuals were put in envelopes and coded by one person (other than anchors) in the control (rehabilitation) and experimental (combination training) groups. The cases were randomly divided. Yoga exercises were performed before the patients were administered by an experienced yoga instructor in the presence of a cardiologist to be approved or adjusted if needed [Table 1]. In addition, all health-care practitioners are present alongside patients to prevent any accidents and maintain balance. Chairs, towels, mattresses, and cushions are also used to comfort and facilitate the movements of the yoga group. Individuals who stopped attending for any reason were excluded from the study (CRT group n = 7 and CT group n = 7). Finally, after completing the 8-week exercise protocol, all variables measured in the pretest were measured and compared again. It should be noted that all tests before and after entering this study were performed on the basis of all ethical principles and were completely voluntary during the study of patients undergoing coronary artery bypass surgery.{Table 1}

All individuals were evaluated for oral hygiene by cortisol and alpha-amylase enzymes. Salivary samples were collected after at least 12 h of nocturnal fasting after awakening in salivary plastic tubes and immediately centrifuged at the Shahid Rajaie Heart Center Laboratory in Tehran for 10 min and 4,000,000 rpm. It was stored at − 70°C until transfer to the laboratory for data analysis.[16] In this study, the alpha-amylase enzyme was measured through saliva at 20 U/L–6000U/L with a sensitivity of 1.95 IU/ml. In this study, cortisol hormone levels were measured in saline at a range of 0.5 ng/ml → 200 ng/ml with a sensitivity of 0.25 ng/ml.


In order to determine the appropriate statistical method, the baseline levels of variables were compared using an independent t-test. Two groups were used for comparison. The confidence coefficient is considered as level (P ≤ 0.05).


The demographic characteristic of individuals is shown in [Table 2]. There were no significant differences in the distribution of these variables among the two groups.{Table 2}

In addition, the results of 8 weeks of combined yoga exercise and rehabilitation on the salivary parameters are presented in [Table 3] and [Table 4] in the dependent and independent t-test results, respectively.{Table 3}{Table 4}

The results showed that the combined intervention of rehabilitation and yoga had a significant effect on salivary cortisol indices (P = 0.028). However, these interventions did not show a significant effect on the alpha-amylase salivary index (P = 0.193). Furthermore, rehabilitation exercise alone had a significant effect on salivary cortisol indices (P = 0.011), but there was no significant difference between groups (P ≥ 0.05).


The results of this study showed that long-term rehabilitation training had a significant effect on cortisol changes in coronary artery disease patients after surgery. In addition, long-term rehabilitation and yoga training had a significant effect on cortisol changes in coronary artery disease patients after surgery. However, there was no significant difference between the effect of long-term rehabilitation training and rehabilitation and yoga on cortisol changes in coronary artery disease patients after surgery. The results also showed that long-term rehabilitation training had no significant effect on alpha-amylase changes in coronary artery disease patients after surgery. Long-term rehabilitation and yoga training had no significant effect on alpha-amylase changes in coronary artery disease patients after surgery. Furthermore, there was no significant difference between the effects of long-term rehabilitation training and yoga on alpha-amylase changes in coronary artery disease patients after surgery.

The findings of the present study disclosed that long-term rehabilitation training and long-term rehabilitation and yoga training had significant effects on coronary artery disease after surgery. However, there was no significant difference between the effect of long-term rehabilitation training and rehabilitation and yoga on cortisol changes in coronary artery disease patients after surgery. The findings of the present study are consistent with the results of Sullivan et al. (2017), Fujisawa et al., Thirthalli et al., and Tayebeh et al., who showed that yoga practice leads to decreased cortisol levels.[17],[18],[19],[20] Similarly, Sullivan et al. (2017) and Fujisawa et al., in separate studies on female students showed that salivary cortisol significantly decreased after yoga practice. A long-term exposure to long-term psychological stress has been reported to be an independent risk factor for CVD and hypertension.[21],[22] Chronic hyperactivity of the SNS and the HPA axis are two of the major stress-related mechanisms at risk for CVD.[23] Exposure to acute stress stimulates SNS, mediated by the release of catecholamines, norepinephrine, and epinephrine, which exert chronotropic and inotropic effects on the heart, leading to increased heart rate and decreased predischarge period which is for vascular stenosis and hypertension.[24] HPA axis activity is also determined by the release of cortisol. The HPA axis regulates blood pressure mainly through cortisol on sodium uptake and homeostasis volume.[25] In summary, the SNS and HPA axis stimulates multiple blood pressure systems, including the renin-angiotensin-aldosterone system. Angiotensin II is released which raises blood pressure through direct vasoconstriction, leading to SNS activation and norepinephrine amplification. Chronic stressors affect the balance of these hormone levels, and repeated life stresses over time have been reported to decrease HPA axis sensitivity to single daily and reactive cortisol levels, as well as increasing SNS activity sensitivity during acute stress.[25],[26],[27]

Although the precise mechanism of the effect of yoga exercise on cortisol changes is still unclear; there are different mechanisms to account for changes in the concentration of resting cortisol levels following physical activity, such as the HPA axis, temperature-adrenal axis, central, PH changes, SNS, intensity and type of exercise activity, plasma volume and dehydration changes, individuals' level of physical fitness, and lactate and hypoxia accumulation. Some studies have reported that increased lactic acid during vigorous physical activity may stimulate cortisol hormone secretion by stimulating hypothalamic-adrenal axis chemical receptors.[28] Increased training volume seems to decrease endurance performance resulting in decreased catecholamine secretion and sympathetic activity. Increased cortisol secretion has been reported to be dependent on exercise volume, and high-volume exercise may increase secretion.[29] Physical activity proportional to the intensity of exercise increases arginine vasopressin (AVP) release into the bloodstream, in addition, adrenocorticotropic hormone (ACTH), and AVP secretion occur synchronously during exercise. One of the mechanisms that increase HPA axis activity is increased plasma lactate levels. Angiotensin II and interleukins that increase during exercise can activate the HPA axis. It is essential for the HPA axis to be activated when activating the message through the afferent nerve. Messages from active muscles and changes in volume and osmolarity increase AVP secretion from the hypothalamus during physical activity, which increases ACTH secretion in the anterior pituitary. ACTH, in turn, increases cortisol secretion from the adrenal glands.[30] Therefore, in the present study, long-term rehabilitation training and long-term rehabilitation and yoga training through an effect on the HPA axis may reduce cortisol levels in coronary artery disease patients after surgery. In general, it has been suggested that the increase in central temperature and the decrease in pH that occur during physical activity are both biochemical reasons to justify changes in cortisol concentration following physical activity. One of the most important factors affecting cortisol secretion is stress. Practicing yoga and especially Shavasana (relaxation) reduces stress and subsequently cortisol hormone depletion. Regarding the lack of significant difference between long-term rehabilitation and yoga training modalities, it is possible that the parameters of both training modes had the same consistency on tone vagina and that the training method did not have a significant difference in cortisol. Some studies have also reported no change or increase in cortisol levels in different populations after exercise.[31],[32]

As can be seen, there have been many studies on the effect of exercise on cortisol changes, which have been reported with respect to differences in the type and intensity of activity, different individuals, and the timing of the inconsistent results. The inconsistency in changes in cortisol activity in previous studies may be due to reliance on distinct sampling methods. Other methodological issues that may result from inconsistency in the findings include the type of exercise style, repetition and duration of sessions, length of training, small sample sizes, and statistical considerations.

The findings of this study showed that long-term rehabilitation and long-term rehabilitation and yoga did not significantly affect alpha-amylase changes in coronary artery disease patients after surgery. Furthermore, there was no significant difference between the influence of long-term rehabilitation training and rehabilitation and yoga on alpha-amylase changes in coronary artery disease patients after surgery. Consistent with the findings of the present study, Furtado et al. showed that sitting yoga exercises in elderly women for 14 weeks and 2 times per week had no significant difference in salivary alpha-amylase and cortisol.[33] In the present study, long-term rehabilitation training and long-term rehabilitation and yoga training did not have a significant effect on alpha-amylase changes in coronary artery disease patients after surgery. Alpha-amylase has been reported to have a circadian rhythm, and the interaction of time of day (morning and evening) and exercise activity had an effect on salivary α-amylase levels;[34] thus, in the present study, this variable could possibly have been affected by different surface responses. Alpha-associated salivary amylase (2004) have presented that salivary alpha-amylase can represent SNS activity.[35]

The sympathetic stimulation appears to increase salivary protein secretion and parasympathetic stimulation decreases salivary concentration and consequently increases salivary fluidity.[36] It has also been reported that salivary alpha-amylase levels are associated with norepinephrine changes that result from physical stimuli (such as exercise) or psychological stimuli.[37] Alpha-amylase works under the function of beta receptors and epinephrine can have an inhibitory effect on salivary secretions, hence the findings of this study are limited by the lack of catecholamine measurement.

In a study examining the effects of yoga on salivary alpha-amylase and cortisol function in prehypertensive adolescents, Sieverdes et al. found that hatha yoga had beneficial changes in blood pressure, a decrease in SNS activity which was associated with a decrease in salivary alpha-amylase, especially in the prehypertensive group.[11] It has also been reported that increased salivary alpha-amylase as a biomarker provides an immediate response to physical activity.[35],[38] It should be noted that this increase is not strongly dependent and has been reported in studies with even 50% aerobic power and short duration.[39] However, there are some contradictions. For example, the effect of the combination of resistance training with 70% maximal repetition and 2-min rest between each period and whole-body vibration on changes in the ratio of free testosterone to cortisol and the activity of the salivary alpha-amylase enzyme in young footballers was investigated. The results showed that salivary alpha-amylase activity was significantly increased.[32] The results of this study emphasize that the hormone secretion in the body requires an optimal level of intensity and duration of training. Alpha-amylase also responds rapidly to a variety of physiological stressors. In another study, two saliva samples were taken before running as a control and one after a thousand meters as a test in young men. Endurance exercise increased salivary alpha-amylase levels.[40] Another possible mechanism of increased salivary alpha-amylase activity following activation is the release of alpha-amylase stored in membrane secretory granules by beta-receptor stimulation through exercise.[41] Some researchers have attributed the increase in salivary alpha-amylase concentration to dehydration and the decrease in salivary flow due to decreased parasympathetic nerve activity.[42] However, salivary alpha-amylase activity decreased significantly in response to training with a treadmill, wheelchair, and stepper (70% to 80% of maximal heart rate).[43] It has also been reported that salivary alpha-amylase levels decreased after 10 weeks of concurrent aerobic exercise in male and female students.[44] Although the high correlation between the change in salivary alpha-amylase activity and reported lactate threshold is probably more salivary alpha-amylase biomarker for measuring psychological stresses, because of individual differences, such as chronic stress, alter its response in most cases. This results in an abnormal distribution of data collected in experimental studies.[45],[46] As can be seen, very little research has been done on the effect of exercise on alpha-amylase, which has been reported due to differences in the type and intensity of activity, different individuals, and timing of the inconsistent results. In the present study, the combined intervention of long-term rehabilitation and long-term rehabilitation and yoga did not have a significant effect on alpha-amylase changes in coronary artery disease patients after surgery. Therefore, other aspects of the exercise and the characteristics of the individuals following these exercises should probably be considered to benefit from it. As he results can be obtained by considering the cardiovascular responses to factors such as health status, age, sex, race, genetics, fitness level, individual differences, and intensity and duration of the exercise, the present study is justified. Most importantly, the variety of cardiac markers and their measurement and sensitivity in different studies can have different results.


In summary, long-term combined rehabilitation exercise and yoga have had a favorable effect on stress factors after coronary artery bypass surgery in cardiovascular patients. Therefore, this type of rehabilitation exercise is recommended for secondary prevention of CVD. However, further research in this area is recommended, with particular regard to intensity, duration of the training, and a number of individuals.

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Conflicts of interest

There are no conflicts of interest.


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