How Does Yoga Work? Study Sheds Light on Mechanisms of Change

By: 
B Grace Bullock, PhD, E-RYT 500

Have you ever wondered what was behind the magic that you feel at the end of a yoga practice? There are over 2,000 articles related to yoga and health listed on PubMed, a database managed by the National Institutes of Health. These studies suggest that yoga is good for your health, but rarely address how yoga works.

A new review of the yoga literature, published in the Journal of Yoga & Physical Therapy, aims to cast light on how yoga affects the primary systems in your body to keep you healthy. Eighteen peer-reviewed articles studying the underlying effects of practicing yoga were identified and thoroughly examined.

Of the 18 articles identified, five contained original research, and all but one was of fairly low quality. The remaining 13 were clinical reports or reviews of the literature, which provide little detail regarding the methodology used.

Based on the literature provided, physical mechanisms related to the endocrine system and nervous system, as well as metabolism and cardiovascular, respiratory and physical parameters of health were reviewed. The following is a brief synopsis of the results.

Endocrine System

“The strongest evidence in both quality and quantity suggests yoga has a positive impact on hormone regulation,” the authors concluded. Levels of salivary cortisol decreased significantly in a number of the studies and reviews examined. Lower cortisol levels are related to decreases in perceived stress and anxiety, increases in feelings of well-being and improved pain management.

Other effects of yoga practice cited included elevated serotonin production, the release of oxytocin during visualization, and higher levels of melatonin, which are related to improved sleep quality and immunity.

Metabolism

The metabolic effects of yoga have been most intensely studied for diabetes management in general, and glycemic control in particular. Studies suggest that regular asana practice is linked with improved glucose tolerance and insulin sensitivity, and clinically significant changes in fasting plasma glucose (FPG) and postprandial plasma glucose (PPPG) levels.  Each of these is an important indicator of diabetes management.

Nervous System

Yoga is commonly believed to directly influence sympathetic and parasympathetic nervous system activity. Evidence suggests that pranayama, visualization and calming techniques, and physical movement (asanas) increase parasympathetic activation. In addition, they elevate levels of gamma-aminobutyric acid (GABA), and regulate the hypothalamic-pituitary-adrenal (HPA) axis. The latter are related to decreased stress, anxiety and depression and improved subjective well-being.

Circulatory System

Two general mechanisms related to the circulatory system were identified in this review: Lowering blood pressure and improving arterial function. Three studies provided evidence of a number of specific benefits to circulatory health. These benefits included lowering blood pressure, enhancing cardiovagal function, slowing atherosclerosis (hardening of blood vessels) to prevent cardiovascular disease, increasing blood flow, and restoring baroreceptor sensitivity. These are all indicators of heart health and efficiency.

Overall Physical Health

General measures of physical health typically examined in yoga studies include cardiorespiratory fitness, biomechanic indicators like balance and flexibility, and anthropometric indicators such as body mass index (BMI). Yoga interventions designed to increase strength and balance are linked to a decreased risk of fall-related injury in the elderly. Interventions using yoga postures have been found to yield exercise training effects such as lowered resting heart rate and oxygen consumption rate, decreased basal metabolic rate (BMR), and decreased body mass index (BMI) and fat mass. Each of these suggests that yoga may be related to preventing heart disease, diabetes and obesity.

We’ve long known that yoga is mind-body “medicine”, and that its effects are systemic rather than isolated to one or two clinical outcomes. This review suggests that your yoga practice can benefit your overall physical health and well-being in myriad ways. 

 

B Grace Bullock, PhD, E-RYT 500, is the Founding Director of the International Science & Education Alliance, a firm that provides strategic planning, research consultation and assessment design to support the empirically rigorous evaluation and sustainable implementation of programs in education, leadership, health and human services. Grace is an intervention scientist, psychologist, yoga educator and author who has worked extensively in integrated behavioral health settings. Her research, clinical practice, teaching and writing emphasize the incorporation of empirically supported psychotherapy with yoga therapy and mindfulness practices to relieve the symptoms of stress, trauma, anxiety, depression and other psychological illnesses, and to promote healthy relationships. She is Faculty at the Integrated Health Yoga Therapy therapist training program, and Professor of Yoga & Neuroscience at the Taksha University School of Integrative Medicine. Grace is the former Editor in Chief of the International Journal of Yoga Therapy and recipient of a Francisco J. Varela Research Award from the Mind & Life Institute. For more information contact Grace at bgracebullock@me.com or see http://isaeaorg.wix.com/isaea and http://www.mind-bodytherapy.com.

 

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