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‘It’s just survival, I suppose.’ Hatha yoga, mindfulness, and balance:
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There are now 11.6 million people aged 65 or over living in the UK, and the percentage of older people in the UK population has steadily increased since the 1970s, reaching 17.7% in 2015 (Office for National Statistics 2016). It is estimated that by 2040, nearly one in four people (24.2%) will be aged 65 or over (Office for National Statistics 2016). This growing proportion of older people driven by falling fertility rates and longer life expectancy indicates that the UK has an ageing population.
Unfortunately, longer living does not always correspond with quality of living, as many older people experience a decline in physical functioning, which can negatively affect their psychological well-being and quality of life. Apart from common age-related morbidities, one of the major risk factors that older people face is the increased risk of an accidental fall, associated with frailty and poor postural balance. Falls, even those that don’t result in injury, are disabling and strongly associated with negative physiological outcomes including activity constraint, loss of independence, and increased morbidity and mortality (Albert, 2014). The psychological implications of falls may include isolation, fear of falling again, and depression. (Albert, 2014) These implications also have wider negative consequences, placing an economic burden on healthcare services.
Given that optimum health is achieved by ‘a state of complete physical, social and mental well-being, and not merely the absence of disease or infirmity’ (WHO 2004), the need for research that moves beyond pathology and towards identifying interventions that help to achieve optimal physical and psychological states while preventing disease is imperative. While many types of preventative interventions – including resistance and aerobic exercises – have been previously studied and found to be associated with improvements in older people’s functioning (Fiatarone et al. 1990; Leenders et al. 2013), many of them focus solely on the physical aspects of functioning and well-being. To date, the effectiveness of yoga as a preventative intervention that targets both the physical and mental aspects of wellbeing has been comparatively less studied, particularly with older participants.
Therefore, this study’s objective was to research the potential of yoga to provide an accessible intervention that would be enjoyable while helping older people adopt independence- and wellbeing-maintaining behaviours.
Defining Yoga
Yoga, an ancient spiritual system, has been used for thousands of years in Eastern cultures to help cope with health problems. Yoga is often translated as ‘a union’, referring to a unity of body, mind and spirit (Iyengar 1993).
The ultimate purpose of yoga philosophy according to Patanjali, the author who systematised the original source of yoga philosophy in The Yoga Sutras, is ‘chitta vrtti nirodhah’ that can be translated as ‘suppression of the fluctuations of consciousness’ (Iyengar 2005:4). According to Patanjali (Iyengar 2005) the suppression of the fluctuation of consciousness, or stilling the mind can be achieved by following a specific 8-stage yogic path consisting of: yama, niyama, asana, pranayama, prathahara, dharana, dyana and samadhi. The first two stages encompass ethical guidelines followed by asana (physical postures) and pranayama (controlled breathing techniques), and a series of meditative stages that together aim at achieving optimum health, self-improvement and self-realisation. The practice of asana is considered a foundational stage of a wider yoga philosophy by various original yogic sources including Hatha Yoga Pradripika (Rieker 1992). This ancient text advocates step-by-step progression through the stages of yoga, and considers the first two stages concerning ethical behaviour as the obvious foundation for the subsequent stages. The practice starts from attempting to perfect the postures, i.e. gain control over the physical body, and progresses towards more subtle practices such as pranayama and the subsequent stages. The asana practice often referred to as Hatha yoga, is currently the most popular form of yoga taught and practiced in the West.
Hatha yoga practice integrates the physical practice of postures (asanas) with regulated breathing and focused attention. As well as focus on asanas and breathing, a fundamental component of an effective Hatha yoga practice is awareness of moment-to-moment sensations (e.g. Iyengar 2005; Desikachar 1999). In addition, a non-judgmental attitude toward one’s limitations is encouraged during the practice, which is intended to promote self-acceptance and awareness of the dynamic nature of existing personal physical boundaries. For the purposes of this study, the physical practice of Hatha yoga will be referred to simply as 'yoga'.
Yoga in the present day
Recently, yoga has become increasingly popular in the West particularly among young and middle-aged women, and has been widely offered at gyms, yoga studios and health clubs. Yoga has simultaneously received a lot of attention from the scientific community. Its status in clinical settings was advanced considerably especially by Kabat-Zinn and his colleagues’ research into the development of an intervention that included elements of yoga and other contemplative practices to reduce stress (see the Mindfulness Stress Reduction Programme: Kabat-Zinn et al. 1992). Since then, researchers have extensively studied the impact of yoga on physical health, showing that yoga may improve a number of health conditions. Results of recent studies showed that yoga hold promise for improving cardiovascular disease and type 2 diabetes (Innes, Bourguignon, and Taylor 2005), arthritis (Büssing et al. 2012) and cancer survivors’ well-being (Culos-Reed et al. 2012). A vast amount of research also supports claims that yoga has physiological benefits, including improved strength (Greendale et al. 2002; Haslock et al. 1994), mobility and flexibility (DiBenedetto 2005; Garfinkel 1994).
In addition to physiological effects, yoga has been shown to alleviate psychiatric conditions such as depression (Uebelacker et al. 2010), anxiety (Cramer 2013), and post-raumatic stress disorder (Meyer et al. 2012; Telles, Singh, and Balkrishna 2012). It has also been shown that yoga may produce immediate psychological benefits including lowering anxiety (West et al. 2004; Michalsen et al. 2005; Gupta at al. 2006) and improving quality of life and spiritual well-being (Moadel 2007).
Compared with the growing literature on yoga with younger and middle-aged participants, relatively few studies have researched the effect of yoga on older people specifically. Among published studies with older participants, the majority focused on physical well-being, establishing a strong relationship between yoga practice and improvement in physical health (for a comprehensive literature review, see Patel, Newstead and Ferrer 2012). For example, recent studies have shown that yoga significantly improves cardiopulmonary fitness, specifically by reducing blood pressure and respiration rate and increasing breath-holding duration (Fan and Chen 2011; Lau, Yu and Woo 2015). The effect of improved respiratory functions was also present in other studies, including Bezerra et al. 2014, and Santaella et al. 2011. Other studies have noted improved gait speed and general mobility (Tiedemann 2013; Kelley at al. 2014), as well as improved endurance and muscle strength (Fan and Chen 2011; Lau, Yu and Woo 2015). In addition, one study showed that self-reported pain level decreased significantly in yoga participants suffering from rheumatoid arthritis (Bosch et al. 2009). Other studies reported improved flexibility (Fan and Chen 2011; Lau, Yu and Woo 2015; Oken et al. 2006; Grabara and Szopa 2015; Farinatti et al. 2014) and postural balance in response to yoga participation (Oken et al. 2006; Fan and Chen 2011). Relatively few studies have investigated the psychological effect of yoga on older participants, and have focused on cognitive functions as well as overall well-being, nevertheless also showing measured improvement (Gothe and McAuley 2015; Hariprasad et al. 2013).
Two recent studies of the effect of yoga on older people are particularly noteworthy in terms of their methodological excellence and their focus on the psychological dimensions of health. In one robust randomized controlled study, 135 healthy older adults practiced yoga for 6 months and their quality of life scores, as compared to exercise and control group participants, significantly improved in response to the intervention (Oken et al. 2006). Another study of note is a recent randomized controlled trial assessing 120 older adults on quality of life (QOL) and sleep measures pre- and post- yoga intervention (Hariprasad et al. 2013). The results showed that the yoga group’s QOL and sleep scores improved significantly in response to high doses of yoga practice (daily for one month, and weekly until third month). Although the results of these studies are promising, one of the main limitations of these and many other similar studies is a lack of a detailed description of the yoga intervention, which makes the studies difficult to replicate or compare across studies. In addition, combining the practice of asanas with formal meditation and stand-alone pranayama practices in these and many other studies may be considered another limitation, due to the possibility of these additional practices having confounding effects. As a result, it is difficult to tell which component of yoga (whether asana, meditation or pranayama) is related to changes in well-being. Nevertheless, the recent literature on yoga suggests that yoga may provide a wide spectrum of health benefits in practitioners of all ages.
Possible mechanisms underlying the psychological benefits of yoga
Mindfulness
One of the proposed mechanisms to explain the beneficial effect of yoga is the mindfulness component of the practice. The concept of mindfulness has its roots in Buddhist practices, in which focused attention and awareness of the present moment are actively cultivated. Mindfulness is commonly understood to be the state of focused attention and awareness of what is taking place in the present moment. Since Kabat- Zinn’s development of the Mindfulness Stress Reduction Programme (MSRP) that combines the elements of meditation, visualisation and yoga (1992) there has been a growing interest in mindfulness in the research community. Kabat-Zinn was among the first to operationalise the term for use in clinical settings, defining it as ‘moment to moment awareness’, encompassing paying attention on purpose, in the present moment, and non-judgmentally (Kabat-Zinn 1990: 2). Kabat-Zinn and his colleagues were also among the first to study the effect of mindfulness meditation on psychological well- being. They found that the practice of mindfulness meditation over an 8-week period and after a 3-year follow-up significantly reduced anxiety levels (Kabat-Zinn et al. 1992; Miller, Fletcher and Kabat-Zinn 1995). Since then it has been found that mindfulness also promotes emotional regulation by increasing one’s awareness of his or her emotional states (Cohen-Katz et al. 2005). In addition, it was suggested that mindfulness promotes mood regulation by fostering self- acceptance and thus promoting overall well-being (Cohen-Katz et al. 2005).
Although it is well-known that the practice of mindfulness meditation increases the levels of mindfulness (Carmody and Baer 2008; Nyklicek and Kuijpers 2008), relatively little is known about the impact of other contemplative practices, such as yoga, on this skill. The practice of yoga emphasises focused attention and non-judgmental awareness of feelings, sensations and perceptions in the present moment, meaning that developing mindfulness is an integrated component of an authentic yoga practice. This is reflected in the practice of yoga postures and movement sequences, in which a mindful awareness of present experiences is emphasised and encouraged by slowing down the movements and paying close attention to the bodily sensations. Indeed, the physical movement in yoga provides a rich source of mindfulness experiences by offering the opportunity to focus on present- moment interoceptive cues (Kolk 2006).
Since yoga encourages the development of mindfulness, it is possible that enhanced mindfulness or altered perceptions of inner sensations and outer phenomena due to yoga practice will, in line with previous research, impact the practitioner’s affect and their overall emotional well-being. In addition, it is likely that increasing awareness of bodily sensations from regular yoga will help practitioners increase awareness of their muscle tone and joint position. In turn, this may help the practitioners to recognise and alter habitual positioning of their bodies, which may improve control over muscle tension and overall posture in day-to-day living (Krucoff et al. 2010). Thus, it seems likely that increased body-awareness, an important aspect of mindfulness, will impact the yoga practitioner’s postural balance both inside and outside the yoga class.
It is possible that psychological benefits arising in response to yoga practice, including improved emotional well-being and balance, may be partially mediated by the changes in psychological perspective and improved body-awareness that result from increased mindfulness.
Physical movement and neurological explanation
Traditionally it was thought that yoga practices, including physical poses, breath work and meditation, reduce mental tensions through strengthening voluntary muscles and increasing control over the involuntary or autonomic nervous system (Vahia, Vinekar and Doongaji 1966). Indeed, Kolk (2006) demonstrated that the therapeutic effect of yoga is at least partially due to the therapeutic nature of movement-based practice such as Yoga,
Tai Chi, and other mind-body traditions. Kolk (2006) presented neurobiological evidence that physical movement utilised during those practices regulates the nervous system’s responsiveness to stress in patients suffering from post-traumatic stress disorder. It was suggested that these physical therapies may help to ‘rewire’ the brain to moderate emotional stress and reactivity, suggesting that there may be a place for mind-body interventions in Western psychotherapeutic models, which currently do not include them.
Biological explanation
Although it was previously established that yoga significantly decreases heart rate, systolic and diastolic blood pressure (Selvamurthy et al. 1998; Damodaran et al. 2002; McCaffrey 2005), and inflammation (Pullen 2008), while also reducing responsiveness to stress, it is only recently that research has revealed the effect of yoga on biological processes that drive the improvement of health and overall well-being. Specifically, it has been shown that yoga down-regulates the hypothalamic-pituitary-adrenal axis and in turn the sympathetic nervous system (the ‘fight or flight’ part of the autonomic nervous system), which controls the response to stress (Ross and Thomas 2010). This in turn activates the parasympathetic nervous system (or the ‘rest and digest’ part of the autonomic nervous system), which has a calming effect on the central nervous system. It is hypothesized that this effect is achieved via direct stimulation of the vagal nerve, a cranial nerve which interfaces with the parasympathetic control of the heart, lungs and digestive tract (Innes, Bourguignon, and Taylor 2005).
In addition, multiple studies have reported that the down-regulating effect of yoga on the stress responses of the HPA axis and sympathetic nervous system (SNS) is linked to decreasing cortisol (Michalsen et al. 2005; West et al. 2004) and blood glucose (Gokal et al. 2007; Khatri et al. 2007) as well as norepinephrine and epinephrine levels
(Selvamurthy et at. 1998). These findings are important because repeated firing of the HPA axis and SNS may lead to dis-regulation of those systems and ultimately to the development of disease, including diabetes, cardiovascular disease, and autoimmune disorders as well as depression (McEwen 2000; Michalsen et al. 2005).
Further biological evidence for the beneficial effect of yoga comes from research showing that the practice of yoga postures leads to substantial increases of GABA, the main inhibitory neurotransmitter responsible for the reduction of neuronal excitability in the brain, which in turn helps to regulate and calm the activity of the nervous system (Streeter et al. 2012).
The whole article can be accessed via the PDF file below on top of this page.
Unfortunately, longer living does not always correspond with quality of living, as many older people experience a decline in physical functioning, which can negatively affect their psychological well-being and quality of life. Apart from common age-related morbidities, one of the major risk factors that older people face is the increased risk of an accidental fall, associated with frailty and poor postural balance. Falls, even those that don’t result in injury, are disabling and strongly associated with negative physiological outcomes including activity constraint, loss of independence, and increased morbidity and mortality (Albert, 2014). The psychological implications of falls may include isolation, fear of falling again, and depression. (Albert, 2014) These implications also have wider negative consequences, placing an economic burden on healthcare services.
Given that optimum health is achieved by ‘a state of complete physical, social and mental well-being, and not merely the absence of disease or infirmity’ (WHO 2004), the need for research that moves beyond pathology and towards identifying interventions that help to achieve optimal physical and psychological states while preventing disease is imperative. While many types of preventative interventions – including resistance and aerobic exercises – have been previously studied and found to be associated with improvements in older people’s functioning (Fiatarone et al. 1990; Leenders et al. 2013), many of them focus solely on the physical aspects of functioning and well-being. To date, the effectiveness of yoga as a preventative intervention that targets both the physical and mental aspects of wellbeing has been comparatively less studied, particularly with older participants.
Therefore, this study’s objective was to research the potential of yoga to provide an accessible intervention that would be enjoyable while helping older people adopt independence- and wellbeing-maintaining behaviours.
Defining Yoga
Yoga, an ancient spiritual system, has been used for thousands of years in Eastern cultures to help cope with health problems. Yoga is often translated as ‘a union’, referring to a unity of body, mind and spirit (Iyengar 1993).
The ultimate purpose of yoga philosophy according to Patanjali, the author who systematised the original source of yoga philosophy in The Yoga Sutras, is ‘chitta vrtti nirodhah’ that can be translated as ‘suppression of the fluctuations of consciousness’ (Iyengar 2005:4). According to Patanjali (Iyengar 2005) the suppression of the fluctuation of consciousness, or stilling the mind can be achieved by following a specific 8-stage yogic path consisting of: yama, niyama, asana, pranayama, prathahara, dharana, dyana and samadhi. The first two stages encompass ethical guidelines followed by asana (physical postures) and pranayama (controlled breathing techniques), and a series of meditative stages that together aim at achieving optimum health, self-improvement and self-realisation. The practice of asana is considered a foundational stage of a wider yoga philosophy by various original yogic sources including Hatha Yoga Pradripika (Rieker 1992). This ancient text advocates step-by-step progression through the stages of yoga, and considers the first two stages concerning ethical behaviour as the obvious foundation for the subsequent stages. The practice starts from attempting to perfect the postures, i.e. gain control over the physical body, and progresses towards more subtle practices such as pranayama and the subsequent stages. The asana practice often referred to as Hatha yoga, is currently the most popular form of yoga taught and practiced in the West.
Hatha yoga practice integrates the physical practice of postures (asanas) with regulated breathing and focused attention. As well as focus on asanas and breathing, a fundamental component of an effective Hatha yoga practice is awareness of moment-to-moment sensations (e.g. Iyengar 2005; Desikachar 1999). In addition, a non-judgmental attitude toward one’s limitations is encouraged during the practice, which is intended to promote self-acceptance and awareness of the dynamic nature of existing personal physical boundaries. For the purposes of this study, the physical practice of Hatha yoga will be referred to simply as 'yoga'.
Yoga in the present day
Recently, yoga has become increasingly popular in the West particularly among young and middle-aged women, and has been widely offered at gyms, yoga studios and health clubs. Yoga has simultaneously received a lot of attention from the scientific community. Its status in clinical settings was advanced considerably especially by Kabat-Zinn and his colleagues’ research into the development of an intervention that included elements of yoga and other contemplative practices to reduce stress (see the Mindfulness Stress Reduction Programme: Kabat-Zinn et al. 1992). Since then, researchers have extensively studied the impact of yoga on physical health, showing that yoga may improve a number of health conditions. Results of recent studies showed that yoga hold promise for improving cardiovascular disease and type 2 diabetes (Innes, Bourguignon, and Taylor 2005), arthritis (Büssing et al. 2012) and cancer survivors’ well-being (Culos-Reed et al. 2012). A vast amount of research also supports claims that yoga has physiological benefits, including improved strength (Greendale et al. 2002; Haslock et al. 1994), mobility and flexibility (DiBenedetto 2005; Garfinkel 1994).
In addition to physiological effects, yoga has been shown to alleviate psychiatric conditions such as depression (Uebelacker et al. 2010), anxiety (Cramer 2013), and post-raumatic stress disorder (Meyer et al. 2012; Telles, Singh, and Balkrishna 2012). It has also been shown that yoga may produce immediate psychological benefits including lowering anxiety (West et al. 2004; Michalsen et al. 2005; Gupta at al. 2006) and improving quality of life and spiritual well-being (Moadel 2007).
Compared with the growing literature on yoga with younger and middle-aged participants, relatively few studies have researched the effect of yoga on older people specifically. Among published studies with older participants, the majority focused on physical well-being, establishing a strong relationship between yoga practice and improvement in physical health (for a comprehensive literature review, see Patel, Newstead and Ferrer 2012). For example, recent studies have shown that yoga significantly improves cardiopulmonary fitness, specifically by reducing blood pressure and respiration rate and increasing breath-holding duration (Fan and Chen 2011; Lau, Yu and Woo 2015). The effect of improved respiratory functions was also present in other studies, including Bezerra et al. 2014, and Santaella et al. 2011. Other studies have noted improved gait speed and general mobility (Tiedemann 2013; Kelley at al. 2014), as well as improved endurance and muscle strength (Fan and Chen 2011; Lau, Yu and Woo 2015). In addition, one study showed that self-reported pain level decreased significantly in yoga participants suffering from rheumatoid arthritis (Bosch et al. 2009). Other studies reported improved flexibility (Fan and Chen 2011; Lau, Yu and Woo 2015; Oken et al. 2006; Grabara and Szopa 2015; Farinatti et al. 2014) and postural balance in response to yoga participation (Oken et al. 2006; Fan and Chen 2011). Relatively few studies have investigated the psychological effect of yoga on older participants, and have focused on cognitive functions as well as overall well-being, nevertheless also showing measured improvement (Gothe and McAuley 2015; Hariprasad et al. 2013).
Two recent studies of the effect of yoga on older people are particularly noteworthy in terms of their methodological excellence and their focus on the psychological dimensions of health. In one robust randomized controlled study, 135 healthy older adults practiced yoga for 6 months and their quality of life scores, as compared to exercise and control group participants, significantly improved in response to the intervention (Oken et al. 2006). Another study of note is a recent randomized controlled trial assessing 120 older adults on quality of life (QOL) and sleep measures pre- and post- yoga intervention (Hariprasad et al. 2013). The results showed that the yoga group’s QOL and sleep scores improved significantly in response to high doses of yoga practice (daily for one month, and weekly until third month). Although the results of these studies are promising, one of the main limitations of these and many other similar studies is a lack of a detailed description of the yoga intervention, which makes the studies difficult to replicate or compare across studies. In addition, combining the practice of asanas with formal meditation and stand-alone pranayama practices in these and many other studies may be considered another limitation, due to the possibility of these additional practices having confounding effects. As a result, it is difficult to tell which component of yoga (whether asana, meditation or pranayama) is related to changes in well-being. Nevertheless, the recent literature on yoga suggests that yoga may provide a wide spectrum of health benefits in practitioners of all ages.
Possible mechanisms underlying the psychological benefits of yoga
Mindfulness
One of the proposed mechanisms to explain the beneficial effect of yoga is the mindfulness component of the practice. The concept of mindfulness has its roots in Buddhist practices, in which focused attention and awareness of the present moment are actively cultivated. Mindfulness is commonly understood to be the state of focused attention and awareness of what is taking place in the present moment. Since Kabat- Zinn’s development of the Mindfulness Stress Reduction Programme (MSRP) that combines the elements of meditation, visualisation and yoga (1992) there has been a growing interest in mindfulness in the research community. Kabat-Zinn was among the first to operationalise the term for use in clinical settings, defining it as ‘moment to moment awareness’, encompassing paying attention on purpose, in the present moment, and non-judgmentally (Kabat-Zinn 1990: 2). Kabat-Zinn and his colleagues were also among the first to study the effect of mindfulness meditation on psychological well- being. They found that the practice of mindfulness meditation over an 8-week period and after a 3-year follow-up significantly reduced anxiety levels (Kabat-Zinn et al. 1992; Miller, Fletcher and Kabat-Zinn 1995). Since then it has been found that mindfulness also promotes emotional regulation by increasing one’s awareness of his or her emotional states (Cohen-Katz et al. 2005). In addition, it was suggested that mindfulness promotes mood regulation by fostering self- acceptance and thus promoting overall well-being (Cohen-Katz et al. 2005).
Although it is well-known that the practice of mindfulness meditation increases the levels of mindfulness (Carmody and Baer 2008; Nyklicek and Kuijpers 2008), relatively little is known about the impact of other contemplative practices, such as yoga, on this skill. The practice of yoga emphasises focused attention and non-judgmental awareness of feelings, sensations and perceptions in the present moment, meaning that developing mindfulness is an integrated component of an authentic yoga practice. This is reflected in the practice of yoga postures and movement sequences, in which a mindful awareness of present experiences is emphasised and encouraged by slowing down the movements and paying close attention to the bodily sensations. Indeed, the physical movement in yoga provides a rich source of mindfulness experiences by offering the opportunity to focus on present- moment interoceptive cues (Kolk 2006).
Since yoga encourages the development of mindfulness, it is possible that enhanced mindfulness or altered perceptions of inner sensations and outer phenomena due to yoga practice will, in line with previous research, impact the practitioner’s affect and their overall emotional well-being. In addition, it is likely that increasing awareness of bodily sensations from regular yoga will help practitioners increase awareness of their muscle tone and joint position. In turn, this may help the practitioners to recognise and alter habitual positioning of their bodies, which may improve control over muscle tension and overall posture in day-to-day living (Krucoff et al. 2010). Thus, it seems likely that increased body-awareness, an important aspect of mindfulness, will impact the yoga practitioner’s postural balance both inside and outside the yoga class.
It is possible that psychological benefits arising in response to yoga practice, including improved emotional well-being and balance, may be partially mediated by the changes in psychological perspective and improved body-awareness that result from increased mindfulness.
Physical movement and neurological explanation
Traditionally it was thought that yoga practices, including physical poses, breath work and meditation, reduce mental tensions through strengthening voluntary muscles and increasing control over the involuntary or autonomic nervous system (Vahia, Vinekar and Doongaji 1966). Indeed, Kolk (2006) demonstrated that the therapeutic effect of yoga is at least partially due to the therapeutic nature of movement-based practice such as Yoga,
Tai Chi, and other mind-body traditions. Kolk (2006) presented neurobiological evidence that physical movement utilised during those practices regulates the nervous system’s responsiveness to stress in patients suffering from post-traumatic stress disorder. It was suggested that these physical therapies may help to ‘rewire’ the brain to moderate emotional stress and reactivity, suggesting that there may be a place for mind-body interventions in Western psychotherapeutic models, which currently do not include them.
Biological explanation
Although it was previously established that yoga significantly decreases heart rate, systolic and diastolic blood pressure (Selvamurthy et al. 1998; Damodaran et al. 2002; McCaffrey 2005), and inflammation (Pullen 2008), while also reducing responsiveness to stress, it is only recently that research has revealed the effect of yoga on biological processes that drive the improvement of health and overall well-being. Specifically, it has been shown that yoga down-regulates the hypothalamic-pituitary-adrenal axis and in turn the sympathetic nervous system (the ‘fight or flight’ part of the autonomic nervous system), which controls the response to stress (Ross and Thomas 2010). This in turn activates the parasympathetic nervous system (or the ‘rest and digest’ part of the autonomic nervous system), which has a calming effect on the central nervous system. It is hypothesized that this effect is achieved via direct stimulation of the vagal nerve, a cranial nerve which interfaces with the parasympathetic control of the heart, lungs and digestive tract (Innes, Bourguignon, and Taylor 2005).
In addition, multiple studies have reported that the down-regulating effect of yoga on the stress responses of the HPA axis and sympathetic nervous system (SNS) is linked to decreasing cortisol (Michalsen et al. 2005; West et al. 2004) and blood glucose (Gokal et al. 2007; Khatri et al. 2007) as well as norepinephrine and epinephrine levels
(Selvamurthy et at. 1998). These findings are important because repeated firing of the HPA axis and SNS may lead to dis-regulation of those systems and ultimately to the development of disease, including diabetes, cardiovascular disease, and autoimmune disorders as well as depression (McEwen 2000; Michalsen et al. 2005).
Further biological evidence for the beneficial effect of yoga comes from research showing that the practice of yoga postures leads to substantial increases of GABA, the main inhibitory neurotransmitter responsible for the reduction of neuronal excitability in the brain, which in turn helps to regulate and calm the activity of the nervous system (Streeter et al. 2012).
The whole article can be accessed via the PDF file below on top of this page.
