As researchers continue to increase our understanding of what yoga can do for patients with chronic conditions, we very well may be writing prescriptions for yoga poses.
Yoga is a centuries-old tradition with origins in ancient India. Blending physical, mental, and spiritual practice, it seeks to bring about a state of harmony between mind and body through concentration, physical practice, and mental discipline. For many practitioners, yoga is seen as a path to spiritual enlightenment. “What is yoga?” provides more information on the background and history of yoga.
In America, the reported frequency of yoga practice accounted for the second largest relative increase in the use of complementary and alternative medicine between 1997 and 2002.1 The number of people practicing yoga in the United States today has approximately tripled within the past decade and is currently estimated to be between 15 million and 18 million.2 As yoga practice has become mainstream, curiosity regarding its potential as adjunct therapy for various diseases has also increased. Over the past decade, the number of research studies exploring the clinical utility of yoga has grown exponentially. Unfortunately, so has the number of unfounded claims for the ability of yoga to “cure” potentially life-threatening diseases.
As medical professionals, PAs strive to find valid scientific research behind the recommendations we make to our patients, whether this is for a prescription medication, a procedure, or a lifestyle change. What is the current state of research on the ancient practice of yoga, and what are the potential benefits for our patients? We are aware that regular physical exercise can help prevent many chronic conditions and is an important therapeutic intervention for many as well. Does yoga practice offer similar benefits?
As we will see, the very nature of yoga can make it awkward to examine in an objective, evidence-based manner. Some yoga practitioners argue that yoga's holistic and integrated approach to mental, physical, and spiritual health makes it impossible to evaluate within the confines of research science and the randomized, controlled trial (RCT).3 Indeed, many practitioners point to the very lack of reproducible scientific research as evidence that yoga has a holistic effect on the body and mind that may not be easily quantified as a statistical variable in a study.3-5 Scientifically trained PAs may find this holistic approach to health a challenge to accept. In addition, the integrated mind/body nature of yoga may itself impede the effort to tease out the specific aspects of the practice that might have a measurable, statistically significant, and reproducible effect on a patient's health status. A lack of standardized teaching practices as well as the wide variety of styles and approaches to yoga confound and influence the applicability of even the most well-designed research studies comparing those undergoing yoga “treatment” to untreated control groups.
In the published research, study samples tend to be small, biased, and nonrandomized. In addition, training periods tend to be short, and confounding variables are generally not well-controlled.5,6 Nevertheless, this article reviews some of the latest research involving yoga practice. To find out what the literature suggests yoga might and might not be able to do for your patients, settle into half-lotus pose and read on.
YOGA RESEARCH FROM A TO Z
ADHD Eighteen boys with diagnosed attention-deficit/hyperactivity disorder (ADHD) were randomly assigned to either a yoga treatment or a cooperative activities group. After 20 sessions of yoga, the boys showed improvement on a variety of indices, including oppositional behavior, emotional lability, and restlessness or impulsivity. The subjects exhibited a dose/ response curve, with those subjects who participated in additional home practice showing a greater response. The control group showed superior scores on measures of hyperactivity, anxiety, and shyness, as well as social function measures.7
Anxiety A meta-analysis of the research involving yoga interventions for anxiety and related disorders reviewed eight studies conducted during 2004. Overall, this research reported positive results, especially in cases of obsessive-compulsive disorder. However, the authors were quick to point out a generally poor quality of research techniques, inadequacies in methodology, and difficulty comparing studies.8 A Cochrane review of two RCTs that investigated the effectiveness of meditation and yoga on patients with diagnosed anxiety disorders stated that based on the available research, no distinct conclusions can be drawn on the ability of meditation and yoga to be effective for anxiety disorders.9
Asthma To determine the efficacy of Iyengar yoga practice on symptoms and perceived quality of life of people living with asthma, 62 patients with mild to moderate asthma were randomized and divided into two groups. The treatment group performed Iyengar yoga for 4 weeks, and the control group enrolled in a “stretching” program. Both groups underwent spirometry testing and recorded their bronchodilator use, symptoms, and quality of life assessments. At no point in the study did the yoga intervention group show a measured benefit in clinical indices.10
Another small RCT divided 17 subjects into a yoga treatment and a control group. The yoga group engaged in relaxation pranayama (mindful breathing) techniques, yoga postures, and meditation 3 times per week for 16 weeks. Spirometry testing showed little difference between the two groups; however, the yoga group showed improved exercise tolerance and reported relaxation as well as a more positive attitude as measured by questionnaire. This study also showed a trend toward less use of short-acting bronchodilator medication in the yoga group.11
Back pain A 12-week RCT compared viniyoga practice with conventional therapeutic back exercises or a self-help book for 101 patients with chronic low back pain. The yoga group met with one instructor for a weekly 75-minute viniyoga practice. Patients were also encouraged to practice at home daily and were given handouts and an audio CD guide. This group showed greater improvement in functional status, decreased activity restriction, and increased general health compared to the conventional exercise group or the self-help book group at 12 weeks. At 26 weeks posttreatment, the conventional exercise and yoga therapy group did not show a significant difference in outcome, though at all points in time, viniyoga therapy appeared to be more effective than the self- care book. The viniyoga benefit also lasted for months after the intervention.12
Cardiovascular disease A systematic literature review of 70 studies published over the past two decades showed a trend toward beneficial changes in metabolic syndrome risk factors such as insulin resistance, lipid profiles, BP, and anthropomorphic indices. The author noted that by controlling risk factors for metabolic syndrome, a regular yoga practice might possibly reduce the risk of cardiovascular disease (CVD). It is important to note that approximately one-third of the reviewed studies were RCTs and that the majority of the others were uncontrolled or nonrandomized controlled clinical trials.4 A 2002 comprehensive review of the literature on the psychophysiologic effects of hatha yoga concluded that regular hatha yoga practice and a “yoga lifestyle” have the potential to benefit CVD risk indices.5
Cardiovascular fitness A 50-minute hatha yoga routine burns 2.2 to 3.6 kcal/min, the equivalent a very slow walk. Except in persons who are very deconditioned, this type of yoga practice alone is unlikely to have a significant training effect on cardiovascular fitness, pulmonary function, body composition, or fat metabolism.13 More vigorous forms of power or vinyasa yoga require a higher energy output, depending on the method of teaching and selection of asanas (postures). One recent study demonstrated a 7% increase in VO2 max after previously sedentary subjects practiced 8 weeks of yoga training.13 However, the general consensus is that yoga does not provide the significant cardiovascular stimulus necessary to enhance cardiovascular function.14
Carpal tunnel syndrome A randomized, single-blind controlled trial of 42 patients with carpal tunnel syndrome
assigned subjects to either a yoga treatment group or a wrist splint group, each 8 weeks in duration. Twice a week, the yoga group practiced postures specifically designed to strengthen and stretch each joint in the upper body. Yoga participants showed improvement in grip strength, pain levels, and Phalen's sign when compared to the wrist splint group. Nerve conduction studies were not performed.15 A Cochrane review of 21 trials that evaluated the clinical outcome of nonsurgical treatment of carpal tunnel syndrome reported that 8 weeks of yoga practice significantly reduced pain as compared to wrist splinting. The yoga was described as having a “significant short-term benefit,” though the duration of this benefit is unknown.16
Depression A 2004 review of five RCTs that evaluated yoga-based interventions for depression and depressive disorders showed some positive outcomes and no adverse effects on patients' mild to severe depressive disorders. However, poor study design and incomplete methodologic reporting makes this interpretation preliminary.17 An RCT studying 7 weeks of yoga training in a group of breast cancer survivors showed positive changes in emotional function, depression, and mood disturbance.18 “Yoga and stress management” (in the online version of this article) provides more information on this study and others involving the effects of yoga on stress.
Irritable bowel syndrome In an RCT, treatment with loperamide (Imodium) was compared to treatment with a series of 12 yoga postures practiced twice a day for 2 months in a small sample of patients with clinically diagnosed irritable bowel syndrome. Patients underwent measurement of surface electrogastrography, and trait and state anxiety tests were administered before, during, and up to 2 months after treatment. Both intervention groups demonstrated a decrease in bowel symptoms and state anxiety.19
Menopausal symptoms In a recent pilot study, 14 postmenopausal women reported via interview and questionnaire a decrease in the severity and frequency of hot flushes after 8 weeks of 90-minute “restorative yoga” classes. Although this initial finding sounds encouraging, this trial had no control group or objective parameter measurements.20 An RCT studying postmenopausal sleep quality divided 164 women into groups who participated in either 4 months of low-intensity yoga, a moderate-intensity walking program, or a wait-list control group. This study reported no statistically significant interventional effects of any treatment on total sleep quality or on any individual sleep quality domain.21
Multiple sclerosis An RCT of 57 subjects with clinically defined multiple sclerosis were assigned to weekly Iyengar yoga class plus home practice, a cycling program, or a wait-list control group for 6 months. Results showed that both active interventions produced significant improvement in perceived levels of energy and reduced fatigue; however, the specific effects of the yoga practice were not isolated.22 Osteoarthritis In a pilot study, 11 deconditioned, yoganaive subjects with a clinical diagnosis of knee osteoarthritis showed improvements in pain and knee stiffness after 8 weeks of yoga training. The group performed modified Iyengar yoga sessions once a week.23
Seizure disorders In 2000, a systematic review of the published literature revealed that only one study was able to meet the selection criteria for reliable research design. The reviewers concluded that no available evidence pointed to yoga therapy as an efficacious treatment for epilepsy.24
Strength and flexibility In a recent study on the fitnessrelated effects of hatha yoga, 10 yoga-naïve and previously untrained subjects aged 18 to 27 years participated in 85 minutes of pranayama and hatha yoga practice twice a week for 8 weeks. These subjects showed significant improvement in upper and lower body muscular strength, endurance, and flexibility. No statistically significant change in body composition or pulmonary function was observed.13
In a partial RCT with a longer time frame, 54 subjects aged 20 to 25 years participated in either 5 months of yoga instruction or no activity. After that time period, both groups practiced yoga for an additional 5 months. The group practicing 10 months of yoga showed significant improvements in shoulder, trunk, hip, and neck flexibility, as well as a reported improved performance during submaximal exercise testing.25
A well-executed study compared subjects who underwent 24 hours of hatha yoga classes over 8 weeks with a control group. The yoga training group showed a 13% to 35% improvement in flexibility, balance, and muscular endurance. The authors concluded that hatha yoga practice has significant effects on balance and flexibility.26
ADVICE TO PATIENTS
Properly executed, regular, appropriate yoga practice has been shown to help patients improve overall muscular flexibility and strength and improve balance. Yoga demonstrates some efficacy as adjunct therapy for back pain, knee osteoarthritis, and carpal tunnel syndrome. Although yoga should not take the place of traditional, proven therapies, it may have some positive effects on obsessive-compulsive disorder, anxiety, and depression, as well as on conditions that are worsened by stress, such as irritable bowel syndrome, ADHD, and menopausal vasomotor symptoms. Yoga practice may add additional benefit to traditional therapies in managing cardiovascular disease indices, though this benefit may be the result of lifestyle changes that include yoga practice and cannot be attributed to yoga alone.
Although encouraging, many of these conclusions are vague and not yet well defined. Clearly, more research is
needed to more specifically quantify the type, duration, and frequency of practice before more broad recommendations regarding yoga as therapy can be made. For a handout you can give your patients in the meantime, see “Ready to try yoga? Seven steps to help you get started” (in the online version of this article). “Prescribing yoga: The importance of instruction” (also in the online version of this article) describes how to help your patients find a qualified teacher.
CONCLUSION
The current literature demonstrates that important influencing factors are often neither controlled for nor addressed in the design of yoga studies. Though a few of the more recent studies have made significant efforts to improve the quality of research design, larger samples, longer trial periods, and some attempt to categorize or standardize the teaching methods used in the research are still very much needed.
Authors have overwhelmingly concluded that rigorous investigation of yoga should be a high priority. Although definitive answers about the efficacy of yoga as therapy for disease are unlikely to be found across the board, the scientific evaluation of specific aspects of yoga practice is clearlypossible. Well-designed studies will provide some important guidelines regarding what yoga might and cannot do as treatment
or preventive care for specific diseases.
As a potential stand-alone or adjunct therapy, yoga is costeffective and has an overall low incidence of adverse effects. Added to these is the tantalizing suggestion—offered through anecdotal reports, the available research, and experiential reported observation—that there may be more benefits to this practice than meets the eye. Indeed, the National Institutes of Health's National Center for Complementary and Alternative Medicine is currently funding clinical trials to study the effects of yoga on everything from insomnia to diabetes, HIV disease, immune function, and chronic obstructive pulmonary disease. By becoming aware of the various types of yoga practice, what yoga can and cannot do for specific disease conditions, and the factors that make yoga safe, PAs can help patients make informed decisions about incorporating yoga practice into a healthy lifestyle. JAAPA
REFERENCES
1. Tindle HA, Davis RB, Phillips RS, Eisenberg DM. Trends in use of complementary and alternative medicine by US adults: 1997-2002. Altern Ther Health Med. 2005;11(1):42-49.
2. Carrico M. Yoga Journal's Yoga Basics: The Essential Beginner's Guide to Yoga for a Lifetime of Health and Fitness. New York, NY: Henry Holt and Company; 1997.
3. Nayak NN, Shankar K. Yoga: a therapeutic approach. Phys Med Rehabil Clin N Am. 2004;15(4): 783-798, vi.
4. Innes KE, Bourguignon C, Taylor AG. Risk indices associated with the insulin resistance syndrome, cardiovascular disease, and possible protection with yoga: a systematic review. J Am Board Fam Pract. 2005;18(6):491-519.
5. Raub JA. Psychophysiologic effects of Hatha yoga on musculoskeletal and cardiopulmonary function: a literature review. J Altern Complement Med. 2002;8(6):797-812.
6. Luskin FM, Newell KA, Griffith M, et al. A review of mind-body therapies in the treatment of musculoskeletal disorders with implications for the elderly. Altern Ther Health Med. 2000;6(2): 46-56.
7. Jensen PS, Kenny DT. The effects of yoga on the attention and behavior of boys with attentiondeficit/ hyperactivity disorder (ADHD). J Atten Disord. 2004;7(4):205-216.
8. Kirkwood G, Rampes H, Tuffrey V, et al. Yoga for anxiety: a systematic review of the research evidence. Br J Sports Med. 2005;39(12):884-891.
9. Krisanaprakornkit T, Krisanaprakornkit W, Piyavhatkul N, Laopaiboon M. Meditation therapy for anxiety disorders. Cochrane Database Syst Rev. 2006;(1):CD004998.
10. Sabina AB, Williams AL, Wall HK, et al. Yoga intervention for adults with mild-to-moderate asthma: a pilot study. Ann Allergy Asthma Immunol. 2005;94(5):543-548.
11. Vendanthan PK, Kesavalu LN, Murthy KC, et al. Clinical study of yoga techniques in university students with asthma: a controlled study. Allergy Asthma Proc. 1998;19(1):3-9.
12. Sherman KJ, Cherkin DC, Erro J, et al. Comparing yoga, exercise, and a self-care book for chronic low back pain: a randomized, controlled trial. Ann Intern Med. 2005;143(12):849-856.
13. Tran MD, Holly RG, Lashbrook J, Amsterdam EA. Effects of Hatha yoga practice on the healthrelated aspects of physical fitness. Prev Cardiol. 2001;4(4):165-170.
14. Clay CC, Lloyd LK, Walker JL, et al. The metabolic cost of Hatha yoga. J Strength Cond Res. 2005;19(3):604-610.
15. Garfinkel MS, Singhal A, Katz WA, et al. Yoga-based intervention for carpal tunnel syndrome: a randomized trial. JAMA. 1998;280(18):1601-1603.
16. O'Connor D, Marshall S, Massy-Westropp N. Nonsurgical treatment (other than steroid injection) for carpal tunnel syndrome. Cochrane Database Syst Rev. 2003(1):CD003219.
17. Pilkington K, Kirkwood G, Rampes H, Richardson J. Yoga for depression: the research evidence. J Affect Disord. 2005;89(1-3):13-24.
18. Culos-Reed SN, Carlson LE, Daroux LM, Hately-Aldous S. A pilot study of yoga for breast cancer survivors: physical and psychological benefits. Psycho Oncol. 2006;15(10):891-897.
19. Taneja I, Deepak KK, Poojary G, et al. Yogic versus conventional treatment in diarrheapredominant irritable bowel syndrome: a randomized control study. Appl Psychophysiol Biofeedback. 2004;29(1):19-33.
20. Cohen BE, Kanaya AM, Macer JL, et al. Feasibility and acceptability of restorative yoga for treatment of hot flushes: a pilot trial. Maturitas. 2007;56(2):198-204.
21. Elavsky S, McAuley E. Lack of perceived sleep improvement after 4-month structured exercise programs. Menopause. 2007;14(3, pt 1):535-540.
22. Oken BS, Kishiyama S, Zajdel D, et al. Randomized controlled trial of yoga and exercise in multiple sclerosis. Neurology. 2004;62(11):2058-2064.
23. Kolasinski SL, Garfinkel M, Tsai AG, et al. Iyengar yoga for treating symptoms of osteoarthritis of the knees: a pilot study. J Altern Complement Med. 2005;11(4):689-693.
24. Ramaratnam S, Sridharan K. Yoga for epilepsy. Cochrane Database Syst Rev. 2000(3):CD001524.
25. Ray US, Mukhopadhyaya S, Purkayastha SS, et al. Effect of yogic exercises on physical and mental health of young fellowship course trainees. Indian J Physiol Pharmacol. 2001;45(1):37-53.
26. Boehde D, Porcari JP, Greany J, et al. The physiological effects of 8 weeks of yoga training. J Cardiopulm Rehabil. 2005;25(5):290.
INFORMATION FOR PATIENTS
Ready to try yoga? Seven steps to help you get started
There are many styles of yoga that make use of various methods and philosophies, but all forms of physical yoga seek union or balance of the body and mind. A particular style may be unique in its teaching methods, the use of props, or the temperature of the room where classes are held. Many classes offer an integration of styles. Most yoga classes offered in studios and gyms consist of physical poses (also called asanas) that may help improve physical strength, flexibility, balance, and mental focus. There is no particular style of yoga that is better than another. Choose a yoga class based on your preferences, fitness level, and goals. Below are some general guidelines that can help you find the class that fits your needs.
1. Check with your PA
Yoga poses can be beneficial to both body and mind, but like any form of exercise, yoga may also pose an injury risk. Deconditioned individuals may find some of the more rigorous yoga styles too difficult. Certain asanas could potentially worsen back or neck problems. Some yoga postures and formats are not appropriate in pregnancy. In addition, conditions such as carpal tunnel syndrome, arthritis, and low back pain will require some modification of some of the poses. Your PA will advise you as to whether a yoga program is appropriate for you and which precautions you should take before you start your practice.
2. Define your goals
Yoga carries many potential benefits that will differ based on the style of yoga and the experience of the practitioner. Many people wish to practice yoga in order to enhance physical fitness, whereas others are interested in stress management, increased flexibility, or relaxation. Some people might wish to focus more specifically on meditation and the spiritual side of the practice. What are your particular goals? Share them with your instructor, and make sure the class is designed to help you reach them.
3. Set realistic expectations
The benefits of regular yoga practice are not instantaneous. At least 8 weeks of training two to three times a 
week are needed to see measurable changes in strength and flexibility, though you may enjoy the way you feel from a regular practice right away. More rigorous forms of power yoga may enhance your strength but typically do not provide a cardiovascular workout. A traditional hatha yoga class burns about as many calories as a leisurely walk, and even a vigorous power yoga practice is still considered equivalent to a light cardiovascular workout. Although yoga can help improve flexibility, balance, and even core muscle strength, it should be viewed as a part of a fitness program that also includes appropriate cardiovascular and strength training. Finally, while yoga may indeed help you manage stress and improve flexibility, there is no evidence that it cures any disease.
4. Find a class that suits you
Yoga instructors vary in both approach to teaching and personality. There is currently no mandatory national certification for yoga instructors, but ideally your instructor will have several years of experience and will have had some recognized training in his or her area of specialty. He or she should willingly provide references and answer questions if asked. If you find the instructor doesn't meet your needs, don't hesitate to try another class. The instructor should make you feel comfortable and be willing to help you with your practice, regardless of your level of experience.
5. Give yourself time
Once you've found a class and style that feel like a good match for you, know that your first few classes might feel awkward or even frustrating. This is normal as you learn a new physical skill set. Your instructor should be able to guide you through this beginner's stage and help you modify the poses as needed to fit your body. Bear in mind that the benefits of yoga will become evident only if you practice regularly. In time, as you become more familiar with the poses and the breathing, the practice will become more and more enjoyable.
6. Listen to your body
Approach your yoga practice with an open mind, but remember that you should not do any pose that makes you 
physically uncomfortable. There is no perfection in yoga, and ultimately you should never force yourself into a pose that causes pain or discomfort. Yoga class is not a performance but rather an individual journey of mind and body. Take breaks as needed, and ask your instructor to show you modifications for particular poses so you feel more comfortable. Props such as blocks, straps, and bolsters can also be used to help you learn the asanas.
7. Practice
Make an effort to find 15 to 20 minutes to regularly practice the yoga asanas that you have learned. Some people prefer attending a class, but others may wish to practice privately. There are DVDs, videos, and books available to help you along with your home practice.