Yoga began not as a form of physical exercise, but as a practice to achieve spiritual enlightenment and mental discipline. It originated in India about 5,000 years ago, first appearing in religious texts recorded by priests. The word yoga comes from the Sanskrit “Yuj,” meaning “to yoke” or “to unite,” which conveys the goal of connecting the mind, body, and spirit through breathing, meditation, and poses. Yoga did not appear in the U.S. until the late 1800s, where it evolved to place greater emphasis on physical fitness through poses and postures (asanas) and breathing techniques (pranayama) than on spirituality and meditation (dhyana). Some estimates suggest that 300 million people worldwide practice yoga. There are more than a dozen styles of yoga, but most combine poses and movements with breathing exercises and relaxation. Some types incorporate meditation.
Popular Types of Yoga in the U.S.
- Hatha. This includes a mix of styles that focuses on balance, strength, flexibility, breathing, and meditation. The practice tends to be less vigorous, so that beginners to yoga might start here.
- Vinyasa. Also referred to as “flow yoga” or “vinyasa flow,” this more vigorous style emphasizes breathing in a specific way that matches the flowing movements of the poses. The movements are continuous, moving from one sequence to the next, and therefore it can raise the heart rate and body temperature.
- Ashtanga. This type is highly structured, with specific poses taught in six rounds with increasing difficulty. It is a vigorous and faster paced yoga with one pose flowing into the next, and may include a spiritual component. Music is not typically used and a class can last from 90 minutes to two hours. Students are encouraged to move at their own pace but to also challenge themselves.
- Kundalini. This type focuses primarily on “life force energy” also referred to as “prana,” or the Chinese term “chi.” It includes movements that stimulate energy to reduce stress and negative thoughts. A mantra (a statement to help focus thoughts) is introduced, followed by breathing exercises and progressive poses. Meditation and chanting or singing are sometimes included.
- Bikram. This type uses high heat to promote sweating and to relax the muscles quickly and increase circulation. The room temperature is set to 95-104 F, with a humidity of about 40%. Similar to ashtanga yoga, the sessions include a specific sequence of poses and last for about 90 minutes.
- Iyengar. This style strongly emphasizes proper alignment of the body throughout the practice, and holds poses for longer durations. Yoga props like blocks, bolsters, straps, chairs, and even a wall are used to help achieve alignment if a student has an injury, lacks range of motion, or is weak in a specific body part. It is usually a slower-paced style with instructors paying close attention to and correcting their students’ form, making it a good choice for a beginner or those with injuries.
- Yin. This style moves at a slower pace and focuses on holding each pose for an extended time, up to 5 minutes. This stretch-based yoga style helps to release tension and increase blood circulation to the joints like the knees, hips, shoulder, neck, and ankles. It increases flexibility and promotes relaxation.
Westernized variations of yoga
- Power. This is typically a blend of vinyasa flow and ashtanga yoga. The types of poses and the pace will vary depending on the instructor. The quicker pace and challenging poses increase the heart rate, improve flexibility, and strengthen all the major muscle groups. It tends to have less of a spiritual or meditative component.
- Aerial. This style uses traditional yoga poses performed in a hammock that hangs from the ceiling. The hammock offers support with inverted poses like headstands and challenges one’s balance.
- Acro. This style combines yoga and acrobatics. It incorporates traditional poses with the use of a partner. One individual has contact with the ground, usually lying down, and the other is lifted off the ground. There is also a third person to watch the pair, ensuring safety with the lifts. This format can be vigorous and develops strength, flexibility, balance, and technique.
- HIIT. High intensity interval training is a format that has topped the list of fitness trends every year ranked by the American College of Sports Medicine.  HIIT involves short bursts of high intensity bouts of exercise followed by a short rest period. Because of the higher intensity, the duration of a class is shorter around 20-30 minutes. HIIT yoga adopts this concept by incorporating HIIT movements such as jumps and plyometrics with traditional asanas and short rest periods, concluding with a stretch and cool-down. The pace is faster than other formats.
Yoga and Health
The Physical Activity Guidelines for Americans recommend that adults, including those with chronic conditions, aim for 150-300 minutes of moderate-intensity aerobic physical activity weekly.  More vigorous forms of yoga can reach an aerobic level by increasing the heart rate, but all yoga forms can provide physical and mental health benefits. It may complement other exercise formats, as the poses and postures increase flexibility, balance, and strength, all of which can help reduce the risk of injury. The focus on breathing and relaxation helps to lower anxiety and depression, and to increase mental clarity and focus. Because of these effects, yoga has become increasingly popular as a therapeutic method. According to the National Center for Health Statistics, yoga is the most commonly used complementary health approach in adults, particularly in non-Hispanic white women.  About half of American yoga practitioners reported starting yoga to improve their health.  Another 14 million American adults said that yoga had been recommended to them by a physician or therapist. 
Research has shown a beneficial effect of yoga for many chronic diseases, but most of the studies are of low quality so it is hard to make definitive conclusions. Yet because of the varying levels of yoga available that can accommodate beginners and those with injuries, yoga may be an exercise option for those who have not been able to follow other recommended physical activity regimens. 
Meta-analyses of randomized controlled trials found that yoga had a beneficial effect on improving cardiovascular risk factors when compared with usual treatment or no treatment. [4,6] Risk factors measured included blood pressure, heart rate, abdominal fat, blood cholesterol, and insulin resistance. However, the quality of trials was low, due to most having a short duration of 12 weeks or less, small numbers of participants, and differences in the interventions or other study characteristics. However, yoga was found to be a safe exercise in these studies and a potentially useful intervention to support patients with an increased risk of cardiovascular disease.
Hypertension or high blood pressure places one at increased risk of cardiovascular diseases, kidney disease, dementia, and vision problems like retinopathy. Yoga, particularly with its focus on methodical breathing (pranayama) and meditation (dhyana), has been shown in randomized controlled trials to be an effective complementary treatment for hypertension in conjunction with blood pressure lowering medications. [7-8]
Yoga may improve insulin sensitivity in muscles, increase blood circulation, and reduce stress, all of which can play a role in diabetes. Systematic reviews and meta-analyses of controlled trials in adults with type 2 diabetes have found that yoga may improve blood glucose levels, lipid levels, blood pressure, and body composition (waist-hip ratio and body mass index). [9-11] A meta-analysis of randomized controlled trials following people with prediabetes found that compared with the control group (no yoga or just general stretches), the yoga intervention group showed improved fasting blood glucose, lipid levels, and blood pressure.  However, clinical trials on yoga and diabetes tend to be of low quality: lacking a control group, small numbers of patients, and short durations. 
A meta-analysis of randomized controlled trials looked at yoga’s effects on the body composition of adults with normal weight, overweight, and obesity.  Outcome measures included weight, body mass index, body fat percentage, waist circumference, and waist-hip ratio. A significant reduction in body mass index was found only in studies including overweight or obese participants practicing yoga compared with usual care or no specific treatment. The authors reported several limitations with the analysis: a small number of studies available for review, low quality studies, and a high risk of publication bias (i.e., only studies that found a positive outcome on body composition tended to be published). The authors commented that more intensive forms of yoga may cause a higher energy expenditure that could help with weight control, but all forms of yoga can help reduce back and joint pain, which may in turn enable increased physical activity in other forms. Yoga may also decrease stress and depression, which could reduce emotional overeating that leads to weight gain. 
Depression and anxiety
Yoga can reduce depression, especially in the short-term, and a higher frequency of yoga sessions may produce greater benefits. [14-16] Its effects on anxiety and panic disorder are less clear, but it may be useful as a complementary therapy along with cognitive behavior therapy or anti-anxiety medications.  A Cochrane review found that yoga reduced depression and anxiety in the short-term in women diagnosed with breast cancer.  Overall, however, the number and quality of studies on yoga for depression and anxiety are low. Interventions are short, there is often a lack of a control group, and data is insufficiently reported (e.g., specifying the level of yoga instruction provided to participants and the duration of yoga sessions). Therefore, the optimal duration, intensity, and frequency of yoga for these mental health conditions is not known. Studies showing a benefit have found that at least one 60-minute session per week reduced symptoms, with 2-3 sessions per week offering greater benefits. [15,17]
Yoga can improve strength and flexibility, which can help reduce chronic pain conditions. Randomized controlled trials (RCTs) have found yoga to help reduce the intensity of and improve the functional limitations related to chronic lower back pain, when compared with no exercise or usual care. [19-21] In older adults, short-term RCTs of up to 12 weeks found yoga to reduce pain such as caused by osteoarthritis or chronic neck pain when compared with no exercise.  There was less of a difference on pain when comparing yoga with other exercises such as walking, Pilates, or strength training.
A review estimating the value of complementary therapies (based on medical evidence and cost-effectiveness) on chronic low back and neck pain found yoga to provide modest health benefits at a fraction of the cost of pain medications when compared with usual care alone. 
Fitness forms of yoga, like other exercises, carry with it the risk of injury. For example, Bikram yoga performed in high heat may increase the risk of dehydration or even heat stroke in some individuals. Inverted poses like headstands have been associated with headache and worsening glaucoma.  Jumping into a power yoga or 2-hour ashtanga yoga class for the first time is clearly risky, but so is taking a class without a well-trained and experienced yoga instructor.
A meta-analysis of 94 randomized controlled trials that included information on yoga safety found that the practice was generally safe and not associated with a greater rate of adverse events compared with other exercise formats.  However, the authors noted wide variation in the trials, such as the study durations and type of yoga practiced (which can vary greatly in intensity and difficulty). A cross-sectional survey of 1,702 yoga practitioners found that 1 in 5 reported at least one adverse effect, most commonly associated with headstands and shoulder stands. The risk was higher in those with chronic illnesses and those practicing through self-study without supervision. Yet when comparing the rate of adverse effects per total hours practiced, yoga was found to be as safe or safer when compared with other exercise types. 
A formal credential is not required to teach a yoga class, though most studios and gyms in the U.S. require some form of certification. A Certified Yoga Teacher (CYT) indicates a certification from a yoga school, although yoga schools are not regulated and the quality of instruction may vary. A Registered Yoga Teacher (RYT) is registered with the Yoga Alliance, a nonprofit professional membership organization that developed their own compliance and education standards. They list both teachers and training programs (Registered Yoga Schools, or RYS) that meet their standards. An RYT-200 title indicates that the instructor has completed at least 200 hours of training at a RYS, and RYT-500, 500 hours. An instructor lacking a formal yoga credential does not necessarily mean the instructor is not qualified to teach, as they may have several years of yoga training and experience in a format that did not provide a credential. In this case, one may view an instructor’s bio or resume to see where they have trained and for how long they have been teaching. Word of mouth about good quality teachers can also be useful.
- If you are new to yoga, always start with a beginner-level class. If the description does not specify this, ask the instructor or studio before you sign up. A beginner class will introduce the most common yoga movements and how to execute them properly. This will prepare you for more advanced styles.
- Although certain styles of yoga are traditionally slower-paced with more basic poses, there can be wide variability depending on the instructor. Introduce yourself to the instructor at your first class, and inform them of any injuries or physical weaknesses you may have.
- The cost of yoga classes varies. Fitness centers such as YMCAs may offer yoga classes included in the membership fee. Independent yoga studios may charge from $10-$20 per 1 to 1.5 hour class; some offer a monthly community class discounted as low as $5. Private one-on-one or small group yoga sessions may range from $30-$70 per hour. Free online video classes such as those available through YouTube may save money and provide access to high-quality instructors, but this format lacks the watchful eye of an instructor who can provide guidance on proper alignment and modifications based on one’s body type and abilities. Without this, the risk of injury may increase. During the pandemic, some yoga instructors offered live virtual classes (e.g., Zoom) in which they could monitor their students and provide verbal cues, but this lacked the hands-on correction of a student’s form if needed. Additional costs include accessories like yoga mats, yoga blocks, and other assistive aids, although most gyms and studios provide these free of charge.
- Yoga in the U.S. is most commonly practiced among non-Hispanic white, college-educated, female adults.  Research on yoga and health shows potential physical and mental health benefits, but racial and ethnic minorities may lack access to this practice. Barriers include a perceived difficulty level and high cost of classes, clothing, and equipment. Household demands, work schedules, lack of childcare, and lack of transportation to classes are other potential barriers. Offering low-cost or subsidized yoga classes at beginner levels, at various times of day (early morning, evening, weekends), and at local community centers while providing childcare may help address some of these issues.
- Thompson WR. Worldwide survey of fitness trends for 2020. ACSM’s Health & Fitness Journal. 2019 Nov 1;23(6):10-8.
- US Department of Health and Human Services. Physical activity guidelines for Americans, 2nd edition. Washington (DC): US Government Printing Office; 2018.
- Clarke TC, Barnes PM, Black LI, Stussman BJ, Nahin RL. Use of yoga, meditation, and chiropractors among US adults aged 18 and over. US Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Health Statistics; 2018 Nov 1.
- Cramer H, Lauche R, Haller H, Steckhan N, Michalsen A, Dobos G. Effects of yoga on cardiovascular disease risk factors: a systematic review and meta-analysis. International journal of cardiology. 2014 May 1;173(2):170-83.
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- Chu P, Gotink RA, Yeh GY, Goldie SJ, Hunink MM. The effectiveness of yoga in modifying risk factors for cardiovascular disease and metabolic syndrome: A systematic review and meta-analysis of randomized controlled trials. European journal of preventive cardiology. 2016 Feb 1;23(3):291-307.
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- Jayawardena R, Ranasinghe P, Chathuranga T, Atapattu PM, Misra A. The benefits of yoga practice compared to physical exercise in the management of type 2 Diabetes Mellitus: A systematic review and meta-analysis. Diabetes & Metabolic Syndrome: Clinical Research & Reviews. 2018 Sep 1;12(5):795-805.
- Ramamoorthi R, Gahreman D, Skinner T, Moss S. The effect of yoga practice on glycemic control and other health parameters in the prediabetic state: A systematic review and meta-analysis. PloS one. 2019 Oct 16;14(10):e0221067.
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- Gonzalez M, Pascoe MC, Yang G, de Manincor M, Grant S, Lacey J, Firth J, Sarris J. Yoga for depression and anxiety symptoms in people with cancer: a systematic review and meta‐analysis. Psycho‐Oncology. 2021 Mar 24.
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- Quentin C, Bagheri R, Ugbolue UC, Coudeyre E, Pelissier C, Descatha A, Menini T, Bouillon-Minois JB, Dutheil F. Effect of Home Exercise Training in Patients with Nonspecific Low-Back Pain: A Systematic Review and Meta-Analysis. International Journal of Environmental Research and Public Health. 2021 Jan;18(16):8430.
- Groessl EJ, Liu L, Chang DG, Wetherell JL, Bormann JE, Atkinson JH, Baxi S, Schmalzl L. Yoga for military veterans with chronic low back pain: A randomized clinical trial. American journal of preventive medicine. 2017 Nov 1;53(5):599-608.
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