Yoga research review
Section snippets
Yoga practice
In a recent survey, approximately 21 million Americans were noted to practice yoga during the past year [2]. Data from this national health survey suggest that 51% of this sample attended yoga classes. The reasons given for yoga were increasing energy (66%), enhancing immune function (50%) and health and disease prevention (28%). The major conditions included back pain (20%), arthritis (6%) and stress (6%). In this survey, the yoga practitioners were primarily female, young, non-Hispanic white,
Physical fitness, cognitive function and emotional well-being
Several studies have examined the effects of yoga on physical fitness including flexibility, balance, spinal mobility and muscular endurance. Cognitive functions have also been assessed including executive function, attention, processing speed and memory.
Stress and psychological disorders (see Table 3)
Stress and several psychological disorders including posttraumatic stress disorder, depression and anxiety are reviewed in this section. Stress has been recently studied in a couple groups of professionals including dentists and nurses.
Cardiovascular conditions (see Table 4)
The recent literature on the use of yoga with cardiovascular conditions has focused on prehypertension, hypertension, and elevated cholesterol. High blood pressure is a notable risk factor for cardiovascular disease [70].
Pain syndromes (see Table 5)
Just as much as massage therapy research has focused on pain, yoga research (yoga being a form of self-massage) has focused on pain syndromes [1]. Recent research on pain reduction following yoga includes studies on arthritis, headaches, pre-menstrual syndrome, lower back pain and potential mechanisms underlying the relationship between yoga and pain reduction. This research has been primarily based on randomized controlled trials, systematic reviews and/or meta-analyses.
Auto-immune conditions (see Table 6)
Yoga has been used as a complementary treatment for several auto-immune conditions in recent studies. These auto-immune conditions include asthma, chronic obstructive pulmonary disease. Type II diabetes, multiple sclerosis, irritable bowel syndrome and chronic fatigue syndrome.
Immune disorders (see Table 7)
Yoga has recently been studied for its immune effects mainly on the cytokines, both the pro-inflammatory and the anti-inflammatory cytokines. And several yoga studies have been conducted with groups of individuals experiencing HIV and breast cancer.
Aging conditions (see Table 8)
Yoga has also been assessed for several aging problems including balance, mobility and sleep quality. The most common aging conditions have also been studied for yoga effects including osteoporosis, Parkinson's and pulmonary disease.
Potential underlying mechanisms
Potential underlying mechanisms for the general effects of yoga include enhanced vagal activity and changes in brain wave activity. Increased vagal activity has been noted in at least 4 studies. In a pre-post, single arm design yoga was practiced daily for one month under the direction of a yoga instructor [145]. At the end of the month the low-frequency (LF) power spectrum was reduced as was the LF/high-frequency (HF) ratio, suggesting greater vagal activity or parasympathetic control.
Limitations of studies and future directions
Surprisingly, many of the same limitations or potential confounds we reviewed in our 2010 review paper continue to be limitations/confounds of the yoga literature several years later [1]. One of the most significant continuing problems regarding the interventions is that yoga is most often an integrated practice of poses, breathing exercises and meditation. Although the poses predominate most yoga sessions, making yoga a type of physical exercise, it is difficult to parse the effects of the
Acknowledgements
I would like to thank my collaborators, the individuals who participated in these studies and the research associates who assisted us. This research was supported by funding from Johnson and Johnson and from Massage Envy.
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