The Effectiveness of Progressive Muscle Relaxation on Troponin Levels and Anxiety in Women with Chest Pain

Masoumeh Kazemi¹, Mojgan Agah Heris^2*, Mohammad Jalali³, Ezzatollah Kordmira Nikouzadeh¹ and Farideh Doroodgar^2,4

1. Department of Health Psychology, Payame Noor University (PNU), Tehran, Iran.

2. Department of Health Psychology, School of Human Sciences, Payame Noor University (PNU), Tehran, Iran.

3. Department of Cardiology, Shahid Rajaei Hospital, Alborz University of Medical Sciences, Karaj, Iran.

4. Translational Ophthalmology Research Center, Tehran University of Medical Sciences, Tehran, Iran. has context menu

Received: 02 July 2024; Accepted: 30 July 2024; Published: 03 August 2024

Citation: Kazemi Masoumeh, Agah Heris Mojgan, Jalali Mohammad, Kordmira Nikouzadeh Ezzatollah, Doroodgar Farideh “The Effectiveness of Progressive Muscle Relaxation on Troponin Levels and Anxiety in Women with Chest Pain.” J Alter Med Ther (2024): 104. DOI: 10.59462/JAMT.1.1.104.

Copyright: © 2024 Heris A.M. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Abstract

Background: Chest pain in women is a significant health concern often associated with elevated troponin levels and anxiety. Progressive Muscle Relaxation (PMR) has been proposed as a nonpharmacological intervention to address these issues.

Methods: This study was a pre-test-post-test semiexperiment with a control group, involving 40 women with chest pain from Karaj city. Participants were divided into a PMR treatment group and a control group. The PMR intervention comprised 8 sessions of 2 hours each. Anxiety was assessed using Beck’s Anxiety Inventory, the Anxiety Sensitivity Index- Revised (ASI-R), and the Perception of Anxiety Control Questionnaire (ACQ). Troponin levels were measured using specific kits. Covariance analysis was employed for data analysis.

Results: PMR significantly reduced anxiety levels (p=0.007), with a notable decrease in anxiety sensitivity (p=0.024) and an increase in the perception of anxiety control (p=0.036). Furthermore, there was a significant improvement in troponin levels (p=0.033), indicating a positive impact on cardiac biomarkers.

Conclusion: PMR appears to be an effective intervention for reducing anxiety and improving troponin levels in women experiencing chest pain. This suggests a beneficial role for PMR in managing psychological and physiological aspects of chest pain.

Keywords

Chest Pain • Progressive Muscle Relaxation • Troponin • Anxiety • Women’s Health • Perception • Health Interventions • Pain

Introduction

Chest pain is a leading reason for emergency department visits [1]. Approximately 0.6 to 0.7 of heart disease patients experience chest pain [2], with the highest emergency visitation rates among individuals aged 45-64 years [3]. Notably, there are significant gender-based differences in the perception and incidence of chest pain. Women, who constitute the majority of chest pain patients, display greater sensitivity to pain than men [4].

Research highlights the influence of psychological factors like anxiety, pain perception, and mood disorders on chest pain [5]. Anxiety, in particular, is prevalent among chest pain patients [6]. Pardo et al. [7] identified anxiety as a causal factor for chest pain. Anxiety, characterized by negative emotions such as tension, restlessness, apprehension, and worry, is typically future-oriented and general [8]. It manifests both physically and psychologically in individuals experiencing anxiety [9] and often precedes new experiences, potentially impacting actions and self- confidence [10].

Anxiety comprises various components, including emotional, cognitive, physical, and motivational symptoms [9]. Anxiety sensitivity refers to the fear of anxiety symptoms due to perceived harmful social, cognitive, and physical consequences [11]. Individuals’ perception of anxiety control varies, with anxiety classified into high and low spectrums [12]. Addressing psychological issues like anxiety and depression can effectively treat and resolve chest pain in heart patients [13]. Kheirandish et al. [14] also emphasized anxiety’s significant role in chest pain.

Chest pain is a common symptom of heart diseases, ranging from stable heartache to unstable angina and myocardial infarction [15]. Diagnosis relies on clinical findings, electrocardiogram (ECG), and initial biomarker levels, particularly cardiac enzymes [16]. Troponin is a key biomarker for chest pain [17] and a predictive factor for acute coronary syndromes [18]. Studies, such as those by Aghayousefi et al. [19], have examined the impact of psychological factors on cardiac enzymes.

Health psychology acknowledges the role of psychological factors in disease exacerbation and treatment response, including chest pain [20]. Fakhrmoradi et al. [21] further supported the significant influence of psychological factors in cardiac chest pain. Various interventions, including psychological ones, can benefit patients with chest pain [22]. Progressive muscle relaxation (PMR), introduced by Edmond Jacobsen in 1938, is an effective treatment for chronic diseases like cardiac chest pain [23]. It induces mental relaxation by alleviating muscle tension, preventing negative thoughts and emotions such as anxiety [25]. Research by Kazak and Ozkarman [26] demonstrated PMR’s effectiveness in reducing pain intensity.

Given the background, PMR has proven effective for various psychological issues [23, 26] and brings mental peace through complete body relaxation [25]. In Iran, PMR has been implemented for diverse groups like MS patients [25], breast cancer patients [24], and hypertension patients [27]. However, no research has explored PMR’s effectiveness on troponin levels and anxiety in women with chest pain in Iran. Hence, this study aims to investigate the effectiveness of PMR on troponin levels and anxiety in women with chest pain.

Materials and Methods

The study employed a semi-experimental, pre-test-post- test design with a control group and a three-month follow- up period. The target population included all women with chest pain in Karaj city in 2021, with the sample drawn from patients at Shahid Rajaei Karaj Hospital. A targeted sampling approach was utilized [28], selecting participants aligned with the study’s objectives. The sample comprised 40 women, evenly divided into a control group and a PMR test group through random assignment.

Inclusion criteria were a diagnosis of chest pain by a specialist, age of 18 years or above, absence of severe mental disorders like psychosis, no chronic physical diseases as diagnosed by a specialist, and not currently using psychoactive substances, sedatives, or painkillers. Exclusion criteria included development of physical problems disrupting psychotherapy (as diagnosed by a specialist), symptom severity increase during treatment, absence from more than two treatment sessions, concurrent participation in other psychological training or clinical trials, and withdrawal from the study for any reason.

This clinical trial (ID: IR.PNU.REC.1401.056) was registered at Payam Noor University, Dubai branch. Ethical considerations were thoroughly addressed, including obtaining informed consent from all participants and ensuring adherence to ethical guidelines throughout the research process.

The research utilized the following tools for assessing variables:

1. Beck Anxiety Inventory: Developed by Beck in 1988, this questionnaire features 21 four-choice questions, each scored from 0 to 3, reflecting increasing intensity of anxiety The total score ranges from 0 to 63 [29]. Beck and Clark [30] reported its internal consistency as 0.93 and retest reliability as 0.75. In Iran, its reliability was reported as 0.78 using Cronbach’s alpha method, with differential validity between anxious and normal groups shown with a T-value of 12.3 at a significance level of 0.001 [31]. Its validity and reliability in the Iranian population are 0.72 and 0.83, respectively, with an internal consistency of 0.92 [32].

2. Anxiety Sensitivity Index Revised (ASI-R): Prepared by Taylor and Cox in 1998, this scale includes 16 questions on a five-point Likert scale, ranging from 0 (very little) to 4 (very much), with a total score range of 0 to 64 [33]. It assesses three subscales: physical, cognitive, and social concerns. Its internal stability, measured by Cronbach’s alpha, ranges from 0.80 to 0.90, with retest reliabilities of 0.75 (two weeks) and 0.71 (three years) [34]. Beyrami et al. [35] conducted a psychometric analysis in Iran, reporting reliability coefficients of 0.93, 0.95, and 0.97 and a correlation coefficient of 0.56 with the SCL-90 questionnaire.

3. Anxiety Control Questionnaire (ACQ): Developed by Rapi et [36], this 30-question scale is based on DSM standards and uses a 6-point Likert scale. It measures individuals’ perceptions of controlling emotional reactions and external threats, with scores ranging from 0 to 180. The scale has been validated in both clinical and non-clinical populations. Rapi et al. reported a Cronbach’s alpha of 87% to 89% [36], while Najimi et al. [38] in Iran found an initial alpha of 0.62.

4. Troponin Measurement: Venous blood (5-7cc) was collected from participants and processed using centrifugation (3000 rpm for 10 minutes) to separate serum. Serum troponin concentration was measured using the Biomerieux kit and enzyme immunoassay method with final fluorescent detection on the VIDAS device [39].

5. PMR Protocol: Based on Bernstein and Boruk’s protocol [40], this intervention consisted of 8 weekly sessions, each lasting two hours. The sessions encompassed activities for achieving complete muscle relaxation, subsequently leading to mental relaxation (Table 1).

Table 1. Summary of progressive muscle relaxation intervention.

Analysis of covariance methods were employed for hypothesis testing, with post hoc tests for pairwise group comparisons. SPSS version 21 was used for data analysis.

Results

In this study, data from 40 participants were analyzed. The demographic analysis revealed that 66.33% of participants were married and 36.67% were single. Educationally, 20% held a diploma, 31.6% a bachelor’s degree, and 18.3% a master’s degree or higher. Duration of illness varied: 33.3% under 6 months, 28.3% between 6 months and a year, and 38.3% over a year.

Table 2 illustrates changes in anxiety measures. For the PMR group, mean anxiety components decreased from 43.68 (SD=3.65) pre-test to 32.59 (SD=4.01) post-test. Anxiety sensitivity reduced from a pre-test mean of 36.98 (SD=3.58) to 27.58 (SD=2.51) post-test. Perception of anxiety control improved from a pre-test mean of 91.49 (SD=4.68) to 76.67 (SD=5.23) post-test. Troponin levels improved from a pre-test mean of 0.079 (SD=0.047) to 0.047 (SD=0.040) post-test (Table 2).

Table 2. Mean and standard deviation of research variables.

The Kolmogorov–Smirnov test confirmed normal distribution of research variables (p > 0.05). Levin’s test indicated equal error variance across groups (p > 0.05). Multivariate covariance analysis (Table 3) revealed significant differences between groups in anxiety component reduction post-test (F=11.77, p=0.007) and at three-month follow-up (F=35.8, p<0.001).

Table 3. The results of multivariate covariance analysis in anxiety components.

PMR significantly reduced anxiety sensitivity in women with chest pain. This reduction was evidenced in the post- test stage (F=18.76, P=0.024) and at the three-month follow-up (F=14.16, P=0.011), indicating a sustained effect of PMR over time (Table 4).

Table 4. Results of multivariate analysis of covariance in anxiety sensitivity.

PMR significantly enhanced the perception of anxiety control among the participants. This improvement was notable both in the post-test stage (F=23.99, P=0.036) and at the three-month follow-up (F=23.68, P=0.018), suggesting a consistent positive impact of PMR (Table 5).

Table 5. The result of multivariate covariance analysis in the perception of anxiety control.

PMR effectively improved troponin levels in the study participants. This improvement was significant in the post- test stage (F=27.05, P=0.033) and maintained at the three-month follow-up (F=22.69, P=0.020), demonstrating the long-term benefits of PMR on cardiac biomarkers (Table 6).

Table 6. The results of multivariate covariance analysis of direction in troponin levels.

Discussion

This study aimed to evaluate the effectiveness of PMR on troponin levels and anxiety in women with chest pain. The findings indicate that PMR positively influences troponin levels, corroborating the results of Abutalebi et al. [16]. The relationship between cardiac enzymes and psychological factors suggests that psychological states can modulate cardiovascular biomarkers [16]. PMR, by promoting mental relaxation and reducing negative emotions such as anxiety and tension, potentially impacts these biomarkers. It operates by countering the effects of muscle tension and stress on the body. As a non-pharmacological and behavioral intervention, PMR is effective in managing the tension associated with chronic diseases and alleviating anxiety and pain [25]. Therefore, the observed improvement in troponin levels can be attributed to the influence of PMR on psychological factors.

The study also demonstrated that PMR effectively reduced anxiety in women with chest pain, aligning with the findings of Najimi et al. [38], Heydari and Saedi [40], Tabarsi et al. [25], and Liu et al. [41]. PMR enhances mental and psychological capabilities, boosting self-confidence, efficiency, creativity, and inner talents. It balances the posterior and anterior hypothalamus, mitigating the adverse effects of tension and anxiety [25].

Concerning anxiety sensitivity in chest pain patients, PMR addresses the underlying muscle tension associated with anxiety. By teaching patients to discern and control muscle tension and relaxation, PMR provides a physiological counter to anxiety. This relaxation technique effectively reduces anxiety sensitivity by promoting an awareness of muscular states and facilitating deep relaxation [39].

Regarding anxiety components, PMR’s ability to induce deep muscle relaxation directly counters anxiety. This relaxation has profound benefits for patients with chest pain, including improved mental and physical health, better sleep, reduced stress hormones, lower heart rate and blood pressure, decreased heart attack frequency, reduced mortality, and enhanced concentration [42]. PMR’s impact on both physical and psychological states significantly diminishes anxiety components.

A holistic view of PMR’s effectiveness includes its influence on blood flow, oxygen supply, and nervous system activities. This approach enhances pain management and resilience. The improvement in pain management can also be linked to the HPA axis’s role in regulating stress hormones like cortisol, which contributes to pain reduction and immune system strengthening.

The bidirectional communication between mind and body is another vital aspect. Stress relief techniques like PMR impact the central nervous system, facilitating the release of analgesic substances and inhibiting pain neurotransmitters. This leads to reduced sympathetic stimulation and enhanced parasympathetic activation, culminating in muscle relaxation and pain reduction.

Moreover, the relaxation exercises in PMR promote deeper breathing, ensuring adequate oxygen supply to the brain and body. This shift in tension and pain perception fosters a relaxed state, further enhancing the therapeutic impact of PMR.Future research should compare PMR with other therapeutic interventions to further explore its relative effectiveness. It is also recommended to replicate this study in different cultural settings to assess the universality of its findings.

Data Availability

Data generated in this study are available from the corresponding author upon request.

Acknowledgement

We appreciate and thank all the participants who devoted their time to the research by participating in the treatment sessions and completing the research tools in the pre-test, post-test and follow-up stages.

Conflict of Interest

The authors have no conflicts of interest.

Funding

The authors have no financial disclosures.

Author Declaration

The corresponding author hereby declares, on behalf of all co-authors, that this manuscript is not under simultaneous

References

1. Crim, Matthew T., Scott A. Berkowitz, Mustapha Saheed, Jason Miller, Amy Deutschendorf, Gary Gerstenblith, Peter Hill, and Frederick K. Korley. “Novel Emergency Department Risk Score Discriminates Acute Coronary Syndrome among Chest Pain Patients with Known Coronary Artery Disease.” Crit Pathw Cardiol 15 (2016): 138-144.
2. Mulder, Roger, Julie Zarifeh, Joseph Boden, Cameron Lacey, Peter Tyrer, Helen Tyrer, Martin Than, and Richard Troughton. “An RCT of Brief Cognitive Therapy Versus Treatment as Usual in Patients with Non-Cardiac Chest Pain.” Int J Cardiol 289 (2019): 6-11.
3. Harskamp, Ralf E., Simone C. Laeven, Jelle C. L. Himmelreich, Wim A. M. Lucassen, and Henk C. P. M. van Weert. “Chest Pain in General Practice: A Systematic Review of Prediction Rules.” BMJ Open 9 (2019): e027081.
4. Schroeder, Stefanie, Stephan Achenbach, Stephanie Körber, Kerstin Nowy, Martina de Zwaan, and Alexandra Martin. “Cognitive-Perceptual Factors in Noncardiac Chest Pain and Cardiac Chest Pain.” Psychosom Med 74 (2012): 861-868.
5. Meresh, Edwin, John Piletz, and AngelosHalaris. “Noncardiac Chest Pain: Systematic Review of the Literature on Prognosis.” Res Rep Clin Cardiol. (2018): 1-9.
6. Rad, Goodarzi Mohammad, Mitra Joudi, Shima Salehi, Hasan Esmaeili, and Zahra Taghipour. “The Investigation of Anxiety and Depressive Disorders and Its Treatment in Children with Chest Pain.” (2017): 32- 39.
7. Pardue, Caleb M., Kamila S. White, and Ernest V. Gervino. “The Role of Disease Conviction: Exploring Its Effects on Chest Pain and Anxiety-Related Models of Non-Cardiac Chest Pain.” J. Clin Psychol Med Settings 26 (2019): 131-141.
8. Halgin, P. R., and Susan Krauss Whitbourne. Abnormal Psychology: Clinical Perspectives on Psychological Disorders. 4th ed. New York: McGraw- Hill College, (2003).
9. Vesal, Mina, Javad Mollazade, Mohamadreza Taghavi, and Mohamadali Nazarinia. “Prediction of Depression Based on Perception of Pain and Quality of Sleep Due to Pain Catastrophizing in Elderly Patients with Rheumatoid Arthritis.” (2015): 69-80.
10. Faraji, N., Pour S. H. Pashaei, and R. Negarandeh. “The Effect of Pre-Discharge Education and Telephone Follow-Up on Illness Perception and Lifestyle in Patients with Myocardial Infarction.” (2015): 82-91.
11. Taylor, Steven. Anxiety Sensitivity: Theory, Research, and Treatment of the Fear of Anxiety. Routledge, (2014).
12. Choi, Jounghwa. “Taylor, S. (2019). The Psychology of Pandemics: Preparing for the Next Global Outbreak of Infectious Disease. Newcastle upon Tyne, UK: Cambridge Scholars Publishing.” Asian Commun Res 17 (2020): 98-103.
13. Alkhatatbeh, Mohammad J., Khalid K. Abdul-Razzak, Noor A. Amara, and Mohamad Al-Jarrah. “Non- Cardiac Chest Pain and Anxiety: A Possible Link to Vitamin D and Calcium.” J Clin Psychol Med Settings 26 (2019): 194-199.
14. Khairandish, Zahra, Leila Jamali, and Saeedeh Haghbin. “Role of Anxiety and Depression in Adolescents with Chest Pain Referred to a Cardiology Clinic.” Cardiol Young 27 (2017): 125-130.
15. Overbaugh, Kristen J. “Acute Coronary Syndrome.” Am J Nurs 109 (2009): 42-52.
16. Abootalebi, Alireza, Seyyed Mehdi Mirhosseini, Amirreza Sajjadieh-Khajouei, Reza Moayednia, and MalihehJahromi-Dastgerdi. “Comparison of Troponin, High-Sensitivity Troponin, and Copeptin Markers at Different Times in Patients with High-Risk Chest Pain.” J Isfahan Med Sch37 (2019): 580-586.
17. Bassand, Jean-Pierre, Christian W. Hamm, Diego Ardissino, Eric Boersma, Andrzej Budaj, Francisco Fernández-Avilés, Keith A. A. Fox et al. “Guidelines for the Diagnosis and Treatment of Non-ST-Segment Elevation Acute Coronary Syndromes: The Task Force for the Diagnosis and Treatment of Non-ST- Segment Elevation Acute Coronary Syndromes of the European Society of Cardiology.” Eur Heart J 28 (2007): 1598-1660.
18. Burtis, Carl A., and David E. Bruns. Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics. 7th ed. St. Louis, MO: Elsevier Health Sciences, (2014).
19. Aghayousefi, A. R., A. Alipoor, F. Shaghaghi, and N. Sharif. “Relationship between Coping Ways with Stress and IL-6 Immunologic Biomarker in Coronary Heart Disease Patients.” (2013): 155-165.
20. Motovalli Naeni, Afsaneh, and Mohammad Ali Besharat. “Comparing Mindfulness and Self- Regulation in Women with Non-Cardiac Chest Pain and Normal in Tehran City.” Health Psychol 5 (2016): 69-84.
21. Fakhr, Movahedi Ali, Abbasali Ebrahimian, Majid Mirmohammadkhani, and Saiedeh Ghasemi. “Relationship between Chest Pain Severity and Physiological Indexes in Patients with Coronary Artery Disease.” (2016): 140-145.
22. Kisely,  Steve  R.,  Leslie  A.  Campbell,  Michael J. Yelland, and Anita Paydar. “Psychological Interventions for Symptomatic Management of Non- Specific Chest Pain in Patients with Normal Coronary Anatomy.” Cochrane Database Syst Rev 6 (2015).
23. Dikmen, Hacer Alan, and Fusun Terzioglu. “Effects of Reflexology and Progressive Muscle Relaxation on Pain, Fatigue, and Quality of Life during Chemotherapy in Gynecologic Cancer Patients.” Pain Manag Nurs 20 (2019): 47-53.
24. Khodavirdi, T., H. Eskandari, A. Borjali, and N. Farrokhi. “Effects of Progressive Muscle Relaxation on Fatigue in Women with Breast Cancer.” Middle East J Disabil Stud 10 (2020): 152.
25. Tabarsi, Shahrbanoo, Mohammad Mehdi Zakeri, Roya Rezapur, et al. “Effectiveness of Progressive Muscle Relaxation Training on Psychological Distress of Women with Multiple Sclerosis.” Sci J Rehabil Med 7 (2018): 71-79.
26. Kazak, Aysun, and AyseOzkaraman. “The Effect of Progressive Muscle Relaxation Exercises on Pain in Patients with Sickle Cell Disease: Randomized Controlled Study.” Pain Manag Nurs 22 (2021): 177-183.
27. Bahram-Khani,       Mahmoud,      Ahmad      Ali-Pour, Masoud Jan-Bozorgi, and Kamal Barzegar-Ghazi “Effectiveness of Muscle Progressive Relaxation on Perceived Stress in Patients with Essential Hypertension.” J Clin Psychol 3 (2011): 79-88.
28. Cozby, Paul C., Scott Bates, Chris Krageloh, Philippe Lacherez, and Dirk Van Rooy. Methods in Behavioral Research. 11th ed. New York: McGraw-Hill, 2012.
29. Beck, A. T., R. A. Steer, and G. K. Brown. Beck Depression Inventory. New York: Harcourt Brace Jovanovich, 1987.
30. Beck, Aaron T., and David A. Clark. “Anxiety and Depression: An Information Processing Perspective.” Routledge (2015): 41-54.
31. Farhadi, A. “The Efficacy of Cognitive Therapy Based on Presence of Mind in Reduction of Anxiety in Patients with Coronary Heart Disease: With a 2 Month Follow Up.” (2014).
32. Kaviani, Hossein, and A. S. Mousavi. “Psychometric Properties of the Persian Version of Beck Anxiety Inventory (BAI).” Tehran Univ Med J (2008).
33. Poli, A., G. Melli, M. Ghisi, G. Bottesi, et al. “Anxiety Sensitivity and Obsessive-Compulsive Symptom Dimensions: Further Evidence of Specific Relationships in a Clinical Sample.” Pers Individ Differ 109 (2017): 130-136.
34. Reiss, Steven, Rolf A. Peterson, David M. Gursky, et al. “Anxiety Sensitivity, Anxiety Frequency and the Prediction of Fearfulness.” Behav Res Ther 24 (1986): 1-8.
35. Beirami, Mansour, Ebrahim Akbari, Abdollah Qasempour, et al. “An Investigation of Anxiety Sensitivity, Meta-Worry and Components of Emotion Regulation in Students with and without Social Anxiety.” Clin Psychol Stud 2, 8 (2012): 40-69.
36. Rapee, Ronald M., Michelle G. Craske, Timothy A. Brown, et al. “Measurement of Perceived Control over Anxiety-Related Events.” Behav Ther 27 (1996): 279-293.
37. Brown, Timothy A., Kamila S. White, John P. Forsyth, and David H. Barlow. “The Structure of Perceived Emotional Control: Psychometric Properties of a Revised Anxiety Control Questionnaire.” Behav Ther 35 (2004): 75-99.
38. Najimi, Avisa, Karim Asgari, and Mojgan Agah Heris. “Effectiveness of Medication, Healthy Nutrition, Proper Physical Activity Prescription Combined with Emotional Regulation Intervention on Perception of Anxiety Control and Cardiovascular Responses in Female Patients with Coronary Heart Disease.” Daneshvar Med 25 (2017): 21-30.
39. Bernstein, Douglas A., and Thomas D. Borkovec. Progressive Relaxation Training: A Manual for the Helping Professions. 2nd ed. Champaign, IL: Research Press, (1973).
40. Heidari, Alireza, and Sara Saedi. “The Effect of Relaxation and Gradual Stress Removal Accompanied by Biofeedback on the Anxiety of the Students.” J Knowl Res Appl Psychol 12 (2011): 4-11.
41. Liu, Kai, Ying Chen, Duozhi Wu, Ruzheng Lin, and Zaisheng Wang, et al. “Effects of Progressive Muscle Relaxation on Anxiety and Sleep Quality in Patients with COVID-19.” Complement Ther Clin Pract 39 (2020): 101132.
42. Ramasamy, Senthilkumar, Suganya Panneerselvam, Pitchaimani Govindharaj, and Archana Kumar, et al. “Progressive Muscle Relaxation Technique on Anxiety and Depression among Persons Affected by Leprosy.” J Exerc Rehabil 14 (2018): 375.