Yoga is a meditative practice in motion that originated in the ancient Indian religion and tradition. While it started as a spiritual practice, currently there are many scientific studies that confirm the health benefits of yoga. Read on to learn more.
What is Yoga?
Yoga is a meditative practice in motion with its roots going back to ancient India. Yoga is a Sanskrit word which means union. It combines physical postures, deep breathing techniques, meditation, and relaxation.
There are many different forms of yoga, including Hatha, Pranayama, Ashtanga Vinyasa, Kundalini, Bikram, etc.
Hatha yoga focuses on physical and mental strength building poses. Many westernized types of Hatha Yoga are used today to improve overall health and wellbeing.
One variation of Hatha yoga is Iyengar, which focuses on the detail, precision, and alignment of posture and breath control. It helps develop stability, strength, and stamina .
Another Hatha variation, called Pranayama, is also known as breathing exercises that benefit your entire body. Pranayama has shown to increase the blood flow and release toxins from the body. Releasing toxins through deep breathing has shown to promote better sleep .
Ashtanga Vinyasa yoga is a physically demanding yoga practice that involves sequences of yoga postures that are synchronized with the breath. It is physically more demanding than other types of yoga .
Bikram yoga is an intense type of yoga that is practiced in a room heated to 105 °F with 40% humidity. Although it can improve strength and balance in healthy adults, beginners should be careful due to its intense nature .
Yoga Nidra, also called yogic relaxation therapy, is a form of gentle yoga that typically comprises maintaining a Shavasana pose (corpse pose or simply lying comfortably) and guided meditation .
Mechanism of Effect
Heart Rate Variability and the Vagus Nerve
The vagus nerve has broad and far-reaching effects on the human body. Yoga can stimulate the vagus nerve by movement, chanting, and breathing exercises. Some researchers have argued that the vagus nerve may be responsible for some of the positive effects that yoga practice has on the brain and emotions .
By stimulating the vagus nerve, yoga may increase parasympathetic nervous system (PNS) activity. Increased PNS activity, some researchers argue, may result in an increase of γ-Aminobutyric acid (GABA) levels in the brain .
Yoga may increase heart rate variability (HRV) and vagus nerve tone, according to the authors of a meta-analysis of 15 studies. However, the authors also noted a relative lack of high-quality research .
Note: HRV is used for health and fitness and is an indicator of autonomic regulation and vagus nerve health. High HRV is associated with fitness, strength, and resilience to stress.
Several small-scale studies in diverse subject types (e.g., Air Force Academy trainees, healthy young men, university students, and menopausal women) have consistently shown that yoga helps reduce oxidative stress. In these studies, compared to control subjects, those who practiced yoga had [8, 9, 10, 11]:
- decreased oxidized glutathione levels
- decreased nitric oxide levels
- decreased lipid peroxides levels
- increased total glutathione levels
- increased antioxidant enzymes, such as glutathione peroxidase
Health Benefits of Yoga
Yoga is considered a very safe and broadly beneficial type of physical activity. However, it should never be used in place of something your doctor recommends or prescribes. If you have any conditions which may make exercise dangerous, talk to your doctor before joining a yoga class.
Possibly Effective For
Yoga includes meditation, relaxation, and exercise. In many studies, it reduced heart rate, improved breathing, and lowered blood pressure. Some researchers have argued that all of these effects are relevant to the HPA axis and sympathetic nervous system, which can reduce stress , which in turn positively affects overall health.
Yoga practice successfully reduced stress among 419 students with high workloads and increased their overall perception of joy .
2) Cognitive Function
Researchers have identified many ways that yoga could potentially help with cognitive function, such as:
- increasing BDNF 
- activating the vagus nerve 
- reducing oxidative stress and inflammation
- reducing the response to stress
Some researchers have suggested that yoga may increase cognitive function by activating the default mode network (DMN), the part of the brain that is active when the individual is not focused inward to the self nor to the outside world (e.g., during yoga or meditation). Increased DMN function has been associated with improved memory performance in young adults and executive-function tasks in older adults [16, 17].
A single session of yoga was associated with moderate improvements in attention and processing speed in a meta-analysis . Yoga also improved executive function and memory in a meta-analysis of 22 studies .
3) Chronic Pain
Patients who suffer from chronic back pain, fibromyalgia, osteoarthritis, neck pain, or severe migraines and do not wish to take conventional painkillers may turn to yoga and similar practices. According to some studies, yoga had pain-relieving effects when done correctly .
39 patients with fibromyalgia showed improved strength, balance, and pain tolerance during yoga therapy and 3 months after treatment .
Women suffering from pelvic pain may not find relief through normal channels. According to a meta-analysis, yoga helped alleviate pelvic pain and reduced the stress and anxiety associated with this kind of pain .
In patients addicted to opiate painkillers, group medical visits including yoga provided pain relief during withdrawal .
4) Metabolic & Cardiovascular Health
In a meta-analysis that included 2173 participants from 30 clinical trials, yoga as an intervention was effective for weight loss in terms of BMI but not in terms of body fat or waist circumference in overweight/obese subjects. However, yoga had no significant effect on any of these parameters in normal-weight people . Therefore, yoga alone may not be an effective way of reducing weight or body fat. However, by reducing stress and inflammation, it can be beneficial in other ways when combined with diet and increased physical exercise.
Inflammation and Adiponectin
Asthma is an inflammatory disorder that can be affected by the autoimmune system. Breathing, postures, and relaxation yoga exercises may help asthma patients .
A Cochrane review involving 15 randomized controlled trials including 1048 participants found moderate-quality evidence supporting that yoga may improve quality of life and reduce symptoms in asthma patients. In many patients, yoga improved asthma symptoms and reduced medication usage. Practicing yoga, especially the variations that focus on breathing techniques, can ameliorate asthma symptoms .
Some researchers believe that yoga helps with depression by reducing HPA axis dysfunction and inflammation and by increasing BDNF. A randomized controlled trial showed moderate short-term effects of yoga when compared to standard treatments for depression .
Yoga, alone or combined with antidepressants, helped decrease Hamilton Depression Ratings more than antidepressants alone. The decrease in the Hamilton Depression Rating Scale correlated with the increase in serum BDNF levels .
Yoga Nidra helped with depression and anxiety symptoms associated with menstrual disorders .
8) Post-Traumatic Stress Disorder (PTSD)
The normalizing effect of yoga on the stress response system is also believed to help with PTSD. In a meta-analysis of 10 studies, 643 patients with PTSD showed reduced anxiety and stress when participating in a group yoga therapy program .
In a review of 5 studies, women with PTSD, mainly from interpersonal violence involving intimate partners, exhibited reduced PTSD symptoms, depression, and anxiety after participating in Trauma-Sensitive Yoga .
Long-term yoga practice reduced chronic symptoms of PTSD in young adults. Yoga also decreased the chance of being diagnosed with PTSD .
Children suffering from trauma due to abuse or negligence in an urban setting found relief when participating in yoga-based psychotherapy over the course of 12-weeks. Their yoga focused on improving mental health alongside physiological health .
Yoga increased mindfulness and resilience and decreased PTSD symptoms in soldiers returning from or currently serving in the military .
9) Physical Fitness
Performing yoga poses strengthens bones and muscles. It increases flexibility and coordination and protects from injuries. Hatha Yoga was physiologically beneficial to any age group, as long as it was performed properly to reduce any chances of injury. It improved core stability and balance, over the course of a 21-day program, from well-performed standing-stork and side-plank poses [46, 47].
Young women participating in yoga programs had increased upper limb strength and increased abdominal muscle endurance .
Women with increased bone deterioration improved bone mineral density and formation without medication from participation in group yoga focused on improving strength and stability .
In sedentary healthy and older adults, daily yoga practices improved functional fitness outcomes over normal strength and conditioning exercises without the need for extra equipment .
In healthy adults, a 12-week Hatha Yoga program increased lung function, muscle strength and endurance, and overall flexibility without any serious muscle strain, and decreased resting heart rate .
Continued yoga practice improves muscle flexibility and connective tissues surrounding the bones and joints. Yoga helps build and maintain muscle strength .
Yoga also improves balance in male college athletes, which helps with sports performance .
10) Sleep Quality
Older adults who practice yoga regularly reported better overall sleep quality, less disturbed sleep, less use of medications, and they also felt more rested compared to older adults who don’t practice yoga .
Insufficient Evidence For
The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of yoga for any of the below-listed uses. While yoga is considered safe, we recommend talking to your doctor beforehand if you have any conditions that might make physical activity unsafe. Furthermore, never use yoga in place of something your doctor recommends or prescribes.
11) Parkinson’s Disease
10 patients with Parkinson’s disease increased their physiological and psychological functions after participating in an 8-week yoga program .
12) Rehab from Stroke
In a study of 47 recent stroke patients, those who underwent 8-week yoga rehabilitation had improved brain and muscle functions compared to those who did not participate in yoga .
13) Menopausal Symptoms
According to one meta-analysis, yoga helped with menopausal symptoms, including psychological, body-based (somatic), and vasomotor (i.e. hot flashes) symptoms. However, two randomized control trials included in this meta-analysis found no effect .
Some causes of infertility in men include low sperm quality, anxiety, and obesity. Yoga improved sperm quality and motility and reduced anxiety levels, which may improve sex life and help with mild erectile dysfunction .
Obesity can be a contributor to male infertility. Yoga practice, as a form of physical exercise, can be incorporated into a weight loss program .
Mood can also affect fertility and sexual function. After three months of yoga, women reported improvements in stress, anxiety, energy, fatigue, and depression, which improve sex life and increase fertility. They also reported less back pain and headaches .
In combination with fertility treatments, yoga can help women by improving mental relaxation. By practicing yoga, women can lead a healthier lifestyle helping with fertility .
Yoga for Cancer Patients
In cancer resource centers, non-pharmaceutical intervention for pain, stress, and anxiety is crucial to the wellbeing of the patients. Yoga is included in this intervention, which reduced stress and anxiety, improved mood, and increased patients’ perceived health .
Women undergoing treatment for breast cancer showed improved psychological functions after participating in a Bali yoga program. Depression in patients decreased, and the perceived quality of life increased over continuous yoga practice .
In patients undergoing chemotherapy for colorectal cancer, chronic side effects include fatigue, nausea, and muscle weakness. Individual yoga post-chemotherapy is an unconventional method that alleviated these side effects, boosting patients’ motivation to continue with chemotherapy .
Children suffering from fatigue due to chemotherapy and blood stem cell transplantation had increased mobility and strength after yoga including breathing exercises, warm-up exercises, yoga poses, and balancing poses .
Men suffering from prostate cancer undergoing 6 to 9-week radiotherapy had decreased fatigue, increased sexual health, decreased levels of urinary incontinence, and increased the quality of life .
Vivekananda Yoga has beneficial effects on both patients with lung cancer and their family members. The mental health and sleep quality of patients increased, which in turn led to decreased sleep disturbances for family members .
Potential Harm/Side Effects from Yoga
Practitioners may suffer physical injuries during yoga, even when they are supervised by experts. Yoga teachers, who practice more intense stands, are more likely to suffer from adverse events .
In one survey of 110 Ashtanga Vinyasa practitioners, 62% of them reported at least one yoga-related injury, which was mainly muscle sprains and strains .
In traditional yoga, voluntary vomiting is a common cleansing technique. This technique can cause acid reflux symptoms or dental erosion. However, this practice is rare in North America or Europe .
Pranayama, which focuses mainly on breathing techniques, is not appropriate for beginners. Some extreme breathing techniques resemble hyperventilation, which can cause problems in people who do not know how to control their breathing .
Bikram yoga is practiced in a room heated to 105 °F with 40% humidity and is physically intense. The intensity and extreme heat during Bikram make it inappropriate for the elderly and people with medical conditions .
Yoga also requires concentration and awareness. It is recommended that practitioners abstain from using drugs or alcohol to avoid injuries during practice .
Finally, people with high blood pressure, glaucoma, lower back pain, and pregnant women should modify or avoid some yoga poses as they may cause injuries or aggravate some conditions .
Fortunately, most yoga poses can be scaled down or made easier to suit the practitioner, so you can consult your physician or qualified healthcare practitioner to determine the extent to which you can practice yoga or if there are any poses to avoid.