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YOGA VERSUS AEROBIC EXERCISE IN MENTAL WELL-BEING
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A Thesis submitted to the faculty o f
San Francisco State University
In partial fulfillment of
the requirements for
the Degree
Master o f Science
In
Kinesiology: Exercise Physiology
by
Katlyn Rae Camper
San Francisco, California
May 2015
Copyright by
Katlyn Rae Camper
2015
CERTIFICATION OF APPROVAL
I certify that I have read Yoga Versus Aerobic Exercise in Mental Well-Being by Katlyn
Rae Camper, and that in my opinion this work meets the criteria for approving a thesis
submitted in partial fulfillment o f the requirement for the degree (Master o f Science in
Kinesiology: Exercise Physiology at San Francisco State University.
Marialice Kern, Ph.D.
Professor
Matt Lee, Ph.D.
Professor
Professor
YOGA VERSUS AEROBIC EXERCISE IN MENTAL WELL-BEING
Katlyn Rae Camper
San Francisco, California
2015
Purpose: The purpose o f this study was to evaluate and compare yoga and
aerobic exercise in its effects of promoting mental well-being in college students. This
study will specifically compare mental well-being and autonomic nervous system
function in college students enrolled in yoga and aerobic activity type course. Methods:
There were a total of 334 participants enrolled in either a yoga or aerobic type activity
course. Each student completed a total of five surveys to assess mental well-being. Based
off indicated interest 32 individuals were randomly selected to participate in measures to
assess heart rate variability, which is an indicator o f autonomic function. Results: There
were no significant differences found between activity type and better overall mental
well-being indicated by the questionnaire. There were also no significant differences
found in heart rate variability indices between groups. Conclusion: Individuals who have
been participating in physical activity for longer periods of time tend to have lower levels
o f stress.
certify that the Abstract is a correct representation o f the content o f this thesis.
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Thesis Committee
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PREFACE AND/OR ACKNOWLEDGEMENTS
This study would not have been accomplished without the constant encouragement and
guidance from my amazingly talented group o f committee members, Dr. Kern, Dr. Lee,
and Dr. Veri. Thank you all for your support over the last couple year. I could not have
picked a better group o f mentors to direct me through this journey. I would also like to
thank the chair of the Kinesiology Department, Dr. Mi-Sook Kim, for helping with the
survey statistics portion. I want to thank my research assistant, Chayanne Robinson, for
all her hard work and time in helping assist me with data collection. I also must thank my
parents who have pushed me to go above and beyond the norms to pursue my lifelong
goals and dreams. Lastly, I want to thank the participants that donated their time to help
me complete this study, without all o f you, none of this would have been possible.
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TABLE OF CONTENTS
List o f Tables................................................................................................................................vii
List o f Figures............................................................................................................................ viii
Introduction.................................................................................................................................. 1
Stress/Immune System ................................................................................................... 2
Heart Rate Variability/ ANS ............................................................................
10
Depression/Anxiety...................................................................................................... 11
Y oga............................................................................................................................... 13
Aerobic E xercise.......................................................................................................... 25
Yoga vs. A ero b ic........................................................................................................... 31
Research Im plications.................................................................................................. 34
M ethods....................................................................................................................................... 35
Participants/Inclusion Criteria.................................................................................... 35
Procedures..................................................................................................................... 36
Statistics......................................................................................................................... 37
R esults........................................................................................................................................... 38
Survey M easures.............................................................................................................38
Physiological M easures............................................................................................... 41
D iscussion.................................................................................................................................... 44
References.....................................................................................................................................48
LIST OF TABLES
Table
Page
1.
Exercise type vs. Survey ....................................................................................38
2.
Pearson Correlation vs. Activity Level ............................................................ 39
3.
Sex differences vs. Surveys ................................................................................40
4.
Physiological descriptive information ............................................................ 41
5.
Heart Rate Variability Indices .......................................................................... 42
vii
LIST OF FIGURES
Figures
1.
Exercise type vs. survey
2. Sex differences vs. Stress
Page
......................................................................................39
...................................................................................41
3.
High Frequency Power between groups
.......................................................... 42
4.
Low Frequency Waves between groups
.......................................................... 43
5.
Total Power between groups
.............................................................................43
6.
LF-HF Ratio between groups
............................................................................44
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1
INTRODUCTION
Stress is a constant factor in today’s society that can potentially jeopardize health
if left unchecked. The stress and stress-induced disorders are fast growing epidemics of
“modern society” (135). Stress is a response to physical or psychological distress that
generates a large number of chemical and hormonal reactions in the body (6). Daily
stressors are necessary for the development of a healthy body, they teach the body to
adapt to daily challenges; but when a stressor becomes chronic, individuals are unable to
control these stressors which can lead to potential disorders such as depression, anxiety,
hypertension, Alzheimer’s and Parkinson’s disease, along with many other health issues
(125). It is now widely believed that the cause of many disease conditions is a complex
interaction between genetics, behavioral factors, and stress (39). Upon entering into
college, students are immersed into a new, challenging, and stressful environment.
Factors that can lead to this are a competitive curriculum, excessive demands on coping
abilities within physical, emotional, intellectual, financial, and social terms, along with
many other contributing factors that lead to high levels o f stress in college students (84).
Apart from periodically and regularly releasing accumulated stress and tension, it is
imperative to move towards a life with eustress. Eustress is essential in the brain’s ability
to retain all the powers and capabilities obtained by a sharp intellect, vital for day-to-day
functioning in a highly competitive and stressful life as a student (84). Yoga and aerobic
exercise are two widely known, supported, and accepted holistic approaches for the
treatment and prevention of stress (56, 155). Yoga shifts a balance from the sympathetic
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nervous system, the flight-or-fight response, to the parasympathetic nervous system,
relaxation response (155), while aerobic exercise in contrast is a stressor that stimulates
the sympathetic nervous system (125). This brings to question which form is more
efficient and beneficial in alleviating the stress that can potentially lead to various
diseases and disorders. Both utilize opposite systems, yet promote similar effects.
Though there are numerous studies that support both forms separately, there are minimal
studies comparing which modality is more favorable for reducing stress. The purpose o f
this study was to compare the differences between two different forms o f physical
activity (i.e. yoga and aerobic) in psychological and physiological indicators o f mental
well-being among college-aged students.
Stress
The term stress is used to encompass a vast number o f differentiated emotional
states (108). The processing and handling o f stress is based off events or circumstances
that are not absolute, but relatively set and reset by positive and negative experiences
(34). Subjective judgments or reactions will be a function of the discrepancies o f the
present stimuli from a neutral point determined by past experiences (34). Psychological
stress occurs when an individual perceives environmental demands to exceed their
adaptive capacity (32). Stress may be external (environmental), internal (emotions), or a
combination of both (84). Elliot and Eisdorfer (1982) used taxonomy to distinguish
stressors and placed them into five categories based on two important dimensions:
duration and course (49). The five-categories of stressors are acute time-limited stressors,
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brief naturalistic stressors, stressful event sequences, chronic stressors, and distant
stressors (133). Public speaking is an example o f an acute time-limited stressor that
involves a brief situational challenge. Brief naturalistic stressors involve a person
confronting a real life short-term challenge such as an academic examination (49).
Stressful event sequences involve a focal event that gives rise to a series o f related
challenges such as a major natural disaster (49). A chronic stressor usually pervades an
individual’s life, forcing one to restructure their identity or social roles; the individual
does not know whether or when the challenge will end (49). A distant stressor forms
because of a traumatic experience that occurred in the past yet still alters their health
because of the long lasting cognitive and emotional stress (49). Although a certain level
o f stress is necessary and results in improved performance, too much stress has negative
effects on health (36).
Stress is not unitary, different demands have different physiological effects (128).
Generally, stressful events are thought to influence the pathogenesis o f a disease by
causing negative affective states (feelings of anxiety and depression), which in turn exert
a direct effect on the biological processes or behavioral patterns that influence disease
risk (1,31). The stress response involves the release o f a variety of substances, including
neurotransmitters, neurotropic factors, hormones, and cytokines, that allow the body to
deal with the challenges of daily life (125). The ability to successfully recover from
stressful events in early life leads to the strengthening o f synaptic connections in neural
networks and a reduction in vulnerability to succeeding stressors (125). On the other
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hand, exposure to chronic stress can be pathogenic and most likely result in long-term or
permanent changes in emotional, physiological, and behavioral responses that influence
susceptibility to diseases and/or disorders such as anxiety, depression, hypertension,
Alzheimer’s disease, and Parkinson’s disease (31). The body can succumb rapidly to
physical stressors with the exception o f chronic, maladaptive stress that has a significant
psychological component (6). It is the psychological and social strain that can continue
on for years. A growing body o f evidence has suggested that long-term psychological
stress can alter basic immune processes (29, 77, 108, 111, 152).
Components o f the immune system
In order to understand the relationship between psychosocial stressors and the
immune system it is important to distinguish between natural and specific immunity. The
cells involved in natural immunity are known as all-purpose-cells. They do not provide
defense against any particular pathogen but can attack a number o f different pathogens
and do so in a short amount of time (minute to hours) (133). The specific immunity is
characterized by greater precision but less speed. Even though the specific immunity
process is efficient in terms o f the number of cells that have to be supported on a daily
basis, it creates a delay of up to several days before a full defense is mounted, therefore,
the body must rely on natural immunity to contain infection during this time (133). The
specific immunity in humans is composed of cellular and humoral responses. The cellular
immune response is mounted against intracellular pathogens such as viruses and the
humoral immune response fights against extracellular pathogens like parasites and
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bacteria (82). An individual’s effort to manage the demands o f stressful experiences may
lead them to engage in certain behaviors that can modify or adapt the immune system
processes (133).
Effect o f acute and chronic stress on immune response
The natural versus specific immune domains affected by stress are consistent with
the duration of a stressor (acute vs. chronic). When stressors are acute and time-limited,
there is an adaptive redistribution o f cells and a preparation o f the natural immune system
(6). Acute stress induces natural immunity, which requires little time and energy
investment to act against invaders (44). The immune system loses the ability to adapt
when a stressor becomes chronic. With an increase in stressor duration, it results in a shift
from potentially adaptive changes to potentially detrimental changes. In comparison with
natural immunity, the specific immune response is activated with chronic stress. The
specific immune system is time and energy intensive, and is only evoked when either a
stressor/ infection persists for a long period of time (6). In general, an appropriate stress
response is initiated by a stressor, sustained for an appropriate time, and then switched
off, allowing for recovery. In contrast, repeated uncontrollable stressors may result in a
lack of adaption, prolonged responses with no recovery period, or inadequate responses
(93). Although there is little known about the psychological pathways that link stressors
with the immune system; it is thought that cytokine expression represents a promising
example of an avenue for research linking stress, immune changes, and disease (133). It
has been hypothesized that chronic stress elicits simultaneous enhancement and
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suppression o f the immune response by altering the patterns o f cytokine secretion and
down-regulating the cortisol receptors (86). This down-regulation, in turn, reduces the
cells’ capacity to respond to anti-inflammatory signals and allows cytokine-mediated
inflammatory processes to flourish (101). The activation of the pituitary-adrenocortical
system is thought to occur during threats appraised as overwhelming (61). The activation
of this system often accompanies chronic stress, as well as clinical depression (53). It has
been suggested that by being able to proactively handle stress in everyday life it could
alleviate the constant activation of the endocrine system, which in turn, increases the
effectiveness of the immune system (6). Findings have suggested a biphasic model in
which acute stress enhances and chronic stress suppresses the immune response (133).
Adaptive Response to Stress
Stress adaptations provide a theoretical framework for understanding the effects
of exercise training on mental well-being (128). Adaptive responses to stress affect
various body systems such as the autonomic, cardiovascular, gastrointestinal, and
immune systems (95). In parallel with behavioral adaption, stress causes physiological
adaption via the central nervous system. A stressor activates the sympathetic system and
acutely depletes levels o f norepinephrine within the brain. Long-term repeated stressors
preserve brain norepinephrine levels allowing the body to adapt to stress in a healthy
manner (18). When stress becomes chronic, synthesis o f norepinephrine is increased to
preserve brain concentrations (128). Stress also activates the central and peripheral opioid
systems, which accounts for some instances of analgesic (pain-relieving) response caused
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by stress (58, 144). The opioid mechanisms have been implicated in mood improvements
o f regular runners (3, 69). The fundamental importance of the opioid response arises from
their inhibitory control of the stress response (128).
The general function o f the immune system is to identify and eliminate foreign,
“non-self’ material that contact or enter the body (108). The immune system is comprised
of a network of glands, nodes, and organs that work together to protect the body from
harmful organisms. The system requires a constant supply o f energy and nutrients to
maintain its optimal function and performance. The effect of stress on the immune system
is mediated by a complex network o f signals that function in a bidirectional manner with
the nervous, endocrine, and immune systems (6). The nervous system to immune system
network involves sympathetic fibers descending from the brain into both primary (bone
marrow and thymus) and secondary (spleen and lymph nodes) lymphoid tissues (51). The
fibers release a variety o f substances that influence the immune response by binding to
receptors of white blood cells (2, 51, 76). The neuro-endocrine immune system network
involves the hypothalamic-pituitary-adrenal axis (HPA), the sympathetic-adrenalmedullary axis (SAM), and the hypothalamic-pituitary-gonadal axis (HPG) (12). The
HPA axis and SAM axis are two of the endocrine response systems that are particularly
reactive to psychological stress (31). Maier and Watkins (1998) discovered that
immunological changes associated with stress were adapted from immunological change
in response to infection, further supporting the relationship between stress and immune
function (83). The immunological activation in human’s results in a syndrome called
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“sickness behavior”, which consists of behavioral changes as well as an increased
responsiveness to pain and depression (83).
HPA
axison immune response
The homeostatic interactions between the hypothalamus, pituitary, and adrenal
glands constitute the HPA axis. The HPA axis controls reactions to stress and regulates
various body processes including digestion, mood, energy use, and the immune system
(6). The hypothalamus synthesizes two pepetides, vasopressin and corticotrophin
releasing hormone (CRH), that regulate the anterior lobe o f the pituitary gland (6). CRH
induces proopiomelanocortin (POMC) synthesis and adrenocorticotropic hormone
(ACTH) (148). ACTH stimulates the synthesis and secretion o f adrenal steroid hormones
(glucocorticoids), especially cortisol, a major stress hormone affecting many tissues in
the body, including the brain (6). Cortisol is the primary affecter o f the HPA axis
activation in humans and regulates a broad range of physiological processes, including
the anti-inflammatory response (31). It acts on two types o f receptors found within the
brain: mineralocorticoid and glucocorticoid receptors expressed by different neurons (6).
Another important target for cortisol is the hippocampus, a major controlling center o f the
HPA axis. Cortisol acts on the hypothalamus and pituitary gland in a negative feedback
cycle to suppress CRH and ACTH production (148). The release o f CRH from the
hypothalamus is influenced by stress, by blood cortisol levels, and by the sleep/wake
cycle (6). Besides the role in the release o f ACTH, CRH serves as a neurotransmitter in
the brain that mediates sympathetic arousal, providing an important link between the
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adrenocortical and autonomic branches of the stress response (6). Glucocorticoid
hormones are capable of inhibiting or down-regulating cytokines, therefore acting as
powerful immune regulators (126). They initially stimulate the immune system and then
help return it to baseline. It is only with major stressors of long durations or with major
exposure to glucocorticoids that the immune system does not return to baseline but into
immunosuppression (126). Cytokines and receptors are expressed in the hypothalamus
and anterior pituitary cells, where they regulate pituitary development, cell proliferation,
and hormone secretion (6). They behave as immune-neuroendocrine modulators by
converting signals that interface stress and inflammation with the HPA axis (146).
Cytokines have been shown to elevate plasma ACTH and glucocorticoid levels in both
animals and human (62, 106, 113). Excessive HPA axis stimulation leads to
immunosuppression and consequently, to an increase susceptibility to infection, thus the
negative regulation of pituitary cytokine function is critical (7). Overall, HPA axis
activation during inflammation is an important protective mechanism to stress.
SAM
axison immune response
In response to the activation o f the SAM axis, catecholamines are released (31).
They work with the autonomic nervous system to exert regulatory effects o f the
cardiovascular, hepatic, and skeletal muscle; along with a variety of immune functions
including cell proliferation, cytokine and antibody production, cytolytic activity, and cell
trafficking (76, 129). In humans, approximately 80% of the catecholamine released is
epinephrine (55). If acutely activated, the SAM axis can provide the body with a needed
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boost to deal with an immediate threat. The typical and most obvious threat o f the stressinduced epinephrine and norepinephrine is the fight-or-flight response, in which there is
an increased heart rate and blood flow to skeletal muscles. If the SAM axis is chronically
activated these molecules can dysregulate immune function (50).
Stress and emotions have been known for some time to be associated with
substantial physiological changes, including the activation o f the two major stress
systems, the HPA and SAM (108). These two systems mediate the effects o f stress on
disease and are engaged during stressful encounters (31). Prolonged or repeated
activation o f these systems can interfere with their ability to control other physiological
systems resulting in an increased risk for physical and psychological disorders (30). The
effects of stress on the regulation of the immune and inflammatory processes have the
potential to influence depression, infections, autoimmune, and coronary artery disease
(54). Evidence has suggested that psychological stress alters the immune system via
direct innervations of lymphatic tissue, through the release of the HPA and SAM
hormones that bind to and alter the functions o f immunologically active cells, or through
stress-induced behavioral changes (31).
Heart Rate Variability and Autonomic Interaction
Heart rate variability (HRV) is thought to be an indicator o f the balance o f the
sympathetic and parasympathetic nervous systems (123). HRV is the beat-to-beat
fluctuations in heart rate or variations in consecutive R-R intervals (148). The amplitude
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and to a lesser degree the frequency o f the fluctuations have been shown to continuously
change as response of cardiovascular control systems via the autonomic nerves (114).
Fluctuations above 0.15 Hz are due to vagal activity only, whereas fluctuations below
0.15 Hz are mediated by both cardiac vagal and sympathetic fibers (114). This
quantitative information of autonomic control can be obtained from HRV. High
frequency (HF) and low frequency (LF) are two components o f HRV that estimate
cardiac vagal (degree of parasympathetic activity) and sympathetic activity (114).
Agreement exists that the HF peak is a good index of vagal activity, thus a decrease in
HF reflects the decrease in vagal activity (21). The interpretation o f LF peak is a bit more
controversial as an expression of sympathetic activity because of the role of both
branches in mediating fluctuations below 0.15 Hz (114). Nevertheless, an increase in LF
has been shown to occur during mental stress when sympathetic activity increased (85).
The LF/HF ratio is a marker of autonomic balance.
Depression and Anxiety
Depression and anxiety are two of the most common mental health disorders, with
an estimated prevalence of 10-20% at any given period (23). An individual’s personal,
social, and occupational functioning, as well as physical health, can be affected
considerably by these disorders (37). According to the American Psychological
Association, anxiety is defined as an emotion characterized by feelings o f tension,
worried thoughts, and physical changes. Individuals suffering from anxiety generally
have intrusive, recurring thoughts or concerns that may lead to the avoidance o f certain
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situations out of worry. Individuals with anxiety disorders may experience a variety of
physical symptoms such as elevated blood pressure, sweating, trembling, dizziness, and
an elevated heart rate. The Anxiety and Depression Association of America claim that 40
million adults, ages 18 and older, suffer from anxiety. Anxiety develops from a variety of
complex risk factors including a genetic predisposition, brain chemistry, personality, and
life events (40). Anxiety has been included in the socio-biological organizations for its
probable adaptive values, as it signals potential danger and can contribute to mastery o f a
difficult situation and thus personal growth (57). Excessive anxiety, on the other hand, is
maladaptive, either because it is too intense or because it is inappropriately provoked by
events that present no real danger (57). Anxiety becomes pathological when thoughts
become excessive and no longer serve to signal danger. It is considered a major
component o f an unhealthy lifestyle and contributes to the pathogenesis of not only
psychiatric but also systemic disorders (66, 130). Therefore, it is important to reduce the
level o f anxiety as a part of the prevention and management of disease.
Depression affects the way one thinks, feels, behaves, and functions (147).
Individuals suffering from depression may experience a lack of interest in daily life, have
an inability to concentrate, experience feelings of worthlessness or excessive guilt, and
express recurrent thoughts of death or suicide. They may experience a lack of energy,
significant weight loss or gain, insomnia or excessive sleeping (41). The Anxiety and
Depression Association of America states that at any given point in time, 3-5 percent of
people suffer from major depression and the lifetime risk is about 17% (147). Depression
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is often a chronic relapsing condition, with relapse rates o f 50-80% in those who have
been depressed in their lifetime (147).
It is not uncommon for someone with an anxiety disorder to also suffer from
depression or vice versa. Mood and anxiety disorders tend to be chronic and highly comorbid with each other (5). Approximately 20-25% o f persons who experience major
stressful events develop depression and/or anxiety (31). Reduced HRV has been noted in
patients with depression and anxiety, indicating decreased activity of the parasympathetic
nervous system and increased activity of the sympathetic nervous system (78). Numerous
studies have supported and demonstrated the efficacy o f yoga and aerobic exercise
interventions as methods of managing and reducing stress, anxiety, and depression (155).
While modern medicine has the ability in many cases to heal physical diseases and
alleviate psychological disorders, it is argued that purely a medical approach is far less
effective in healing the emotional, intellectual, and personality layers o f the human entity
(155).
Yoga
Yoga is an ancient discipline designed to bring balance and health to the physical,
mental, emotional, and spiritual dimensions o f an individual (123, 135). The Sanskrit
name for yoga is “yuj” which means union, to join, to direct, and concentrate one’s
attention (155). Yoga means union o f our individual consciousness with the universal
divine consciousness in a super-conscious state known as Samadhi (149). The reflection
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of the union of the body, mind, and spirit is what differentiates yoga from general
exercise programs (43). The goal of the ancient traditional yoga is the stilling of
restlessness in the mind and the joining of the mind, body, and spirit in the search for
healing self-awareness and spiritual attunement (33). Although yoga developed from and
within Indian philosophy and religion, the practice o f yoga itself does not require spiritual
beliefs or religious observation (99). An internationally renowned ashtanga yoga
instructor, Sharath Jois, stated that “yoga itself does not have religion; it is the
transformation for well-being.” The main goals o f yoga are to achieve tranquility of the
mind and create a sense of well-being. Yoga suspends the fluctuations of the mind and it
is believed that by acting consciously, we live better and suffer less (155).
Yoga was first described by Patanjali in the classic text, Yoga Sutras (13, 79).
Patanjali defined the purpose of yoga as the knowledge of the true “s e lf’ (16). Yoga
Sutras outlined the eightfold path to awareness and enlightenment called Ashtanga, which
means “eight limbs” (79, 81). The eight limbs are comprised of ethical principles for
living a meaningful and purposeful life (79, 81, 155). They direct attention towards one’s
health while acknowledging the spiritual aspects o f one’s nature (155). The eight limbs
are yama (universal ethics), niyama (individual ethics), asana (physical postures),
pranayama (breath control), pratyahara (control o f the senses), dharana (concentration),
dyana (meditation), and sakadhi (bliss) (93). It is thought that each limb is connected as a
whole, in the same way that bodily limbs are all connected.
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There are four basic principles that underlie the teaching and practices o f yoga’s
healing system. First, it is important to keep in mind that the human body is a holistic
entity comprised o f interrelated dimensions that are inseparable from one another (41).
Secondly, every individual and their needs are unique and must be approached in a way
that acknowledges this individuality (41). Yoga is self-empowering; the student is their
own healer (28). Thirdly, the healing comes from within; yoga only assists in engaging
the healing process (155). Lastly, the quality and state o f an individual’s mind is crucial
to healing, a positive mind state leads to a faster recovery.
Components o f yoga
Yoga consists o f a complex system o f spiritual, moral, and physical practices
aimed at attaining ‘self-awareness’ and well-being (117). Integrated yoga practice
includes aspects of exercise (asanas), breath manipulation (pranayama), and relaxation
(meditation) (74). It is thought that by unifying the physical body, breath, and
concentration while performing postures will clear the blockages in the energy channels
of the body and the body’s energy system will become more balanced (33). All the
components of yoga play a role and work together collectively to produce the multi­
dimensional positive effects (74).
Asanas are the physical postures that stretch and strengthen different parts o f the
body. An asana may be one o f two types: dhyanasana and shasthyasana. Dhyanasana are
postures that keep the spinal cord free and shifts the center of gravity (135). Shasthyasana
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are the postures that lead to a healthy body (135). Each asana has a purpose, some
postures message and bring fresh blood to the internal organs, while simultaneously
rejuvenating the nervous system and lubricating the joints, muscles, and ligaments (6).
Others stimulate the nervous and circulatory systems that promote coordination and
concentration, and calm the body.
Pranayama involves a variety o f techniques for the regulation of breathing (68).
The Sanskrit word ‘prana’ refers to the light force (33). Breathing techniques combine
inhalation, breathe retention, and exhalation (67). Inhalation is the process of receiving
life energy, retention of breaths holds that energy, and exhalation empties all thoughts
and emotions (68). They can be slower, more regular, or more refined. Common yogic
breathing includes the complete yoga breath (conscious breathing in the lower, middle,
and upper portions of the lungs); interval breathing (duration o f inhalation and exhalation
are altered); and alternate nostril breathing (33). Breath awareness and synchronization of
movement and breath are important in performing the physical postures of yoga (33).
Meditation originated in Asian cultures and is a core component o f Buddhism. It
was derived from the word “meditari” meaning to think, to dwell upon, and to exercise
the mind; as well as the word “mederi” which means to heal (48). The Sanskrit derivation
is “medha”, meaning wisdom (48). Meditation is a mental process involving voluntary
concentration of thoughts aimed at producing an altered state of awareness that is
believed to produce changes in perception, attention, and cognition (122). One of the
more commonly explored types of meditation is Mindfulness Meditation (MM). MM
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originated from ancient Buddhist and Yoga philosophies as a form of Eastern
contemplative practices (48). Mindfulness refers to the process o f intentionally bringing
attention, in a nonjudgmental manner, to the internal and external experiences that exist
in the present moment (27). The three fundamental components of mindfulness are
intention, attention, and attitude. Intention involves motivation and knowing the
conscious direction and purpose (136). Attention relates to the moment-to-moment
knowing o f what is happening as it is actually happening (136). The attitude aspect
describes how one pays attention and refers to accepting, caring, and discerning qualities
of mindfulness (136). Heightened mindfulness creates a better awareness of sensations,
thoughts, consciousness, bodily states, and the environment while simultaneously
encouraging openness, curiosity, and acceptance (48). It is a process that allows the mind
to be still to permit a greater sense o f awareness to the present moment. MM is intended
to cultivate continuous and clear attention to ongoing subjective experiences in
combination with an attitude of acceptance and openness to whatever experiences may
arise (48). The key elements of MM are the ability to intentionally attend to the present
moment regardless of the content observed; the ability to recognize and accurately label
emotions, and creating a refined self-awareness (71). It allows individuals to detach from
thoughts and feelings to gain better insight, awareness, and compassion in order to
facilitate a more flexible and adaptive coping response to stressors (48). Regular practice
o f all these techniques is considered to clear body energy channels, improve circulation to
vital body organs, promote stillness, and concentration (33, 67).
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Hatha yoga
In the Western world, the most common aspects of yoga practice are the physical
postures and breathing practices of Hatha Yoga and meditation. It is the most popular
and widely used form in the West, and is a disciplined, individually paced form of yoga
that places more focus on transitional postures, as well as breathing and meditation (121).
It was developed by T. Krishnamacharya in the first part o f the 20th century (37). There
are numerous styles of Hatha such as Ashtanga, Iyenger, Intergral, and Kripaln (33).
Most people begin with Hatha yoga in order to promote relaxation, enhance flexibility, or
to heal a body injury (131). It enhances the capacity of the physical body through a series
o f body postures, movements, and breathing techniques (33). The physical postures are
performed while standing, sitting, or lying prone or supine on the floor and take each
joint through a full range of motion (131). The postures involve bending, twisting, and
balancing of the body, consequently improving flexibility and strength (117). The
controlled breathing helps to focus the mind and achieve relaxation while meditation
aims to calm the mind (121). The aim of Hatha Yoga is to free the body of physical
limitation and to restore balance to the body (131). Frequent mental distress is
increasingly prevalent among U.S. adults; Hatha yoga has claimed to induce stressreduction and empowerment in practicing subjects (100).
Benefits o f yoga
19
Since the 1970s, meditation and other stress reduction techniques have been
studied as possible treatments to promote well-being (135). The earliest reported benefit
of yoga in alleviating mood and anxiety symptoms was published by Girodo in 1974
(37). As participation rates in mind-body fitness programs continue to increase, it is
important for healthcare professionals to be informed about the nature of yoga and the
evidence o f its therapeutic effects. Mind-body fitness combines muscular activity and an
internally directed mindful focus on awareness o f the self, the breath, and energy (33).
Therapeutic yoga is defined as the application of yoga postures and practice to the
treatment of health conditions (155). It involves instruction in yoga practices and
teachings to prevent, reduce, or alleviate structural, physiological, emotional, suffering,
and limitations. Improved flexibility is the first and most obvious benefit of yoga (90). It
has been shown to promote strength and endurance, improved concentration, selfconfidence, efficacy, lowered irritability, and facilitates in friendliness, compassion,
greater self control, and encourages an optimistic outlook by cultivating a sense of
calmness and well-being (84). A study on two-weekly (90 minute) yoga sessions over
two months, was able to determine the effectiveness o f yoga as a tool for reducing
anxiety levels (70). The researchers suggested that yoga encourages individuals to
become aware o f their body’s tension throughout specific body postures. By raising
awareness of the body and in learning a method by which stress can be reduced, yoga
may serve to increase self-confidence by promoting a personal sense of control (70).
Stress, anxiety, depression, and other psychological debilitating conditions have been
20
associated with cognitive deficits (11). It has been suggested that yoga plays a role in
cognitive aspects of psychological functions such as memory improvement (4); it is
thought that mind-body techniques can have potential beneficial effects on cognition
because they involve active attention exercises (70). Rocha et al. (2012) found
reductions in parameters related to stress, depression, and anxiety, as well as improved
memory after six months of yoga practice. A study performed on the effects of yoga, over
a three-month period, demonstrated improvements in psychological status with
significant decreases in scores of anxiety, depression, anger, along with improvements in
well-being and significant decrease in sympathetic activity (74). Yoga appears to be an
effective method for improving health, and in the prevention and management of
diseases.
Yoga has been shown to be a simple and economical therapeutic modality for
disease. Viewed as a holistic stress management technique, yoga is a form of
complementary and alternative medicine that produces a physiological sequence of
events in the body to reduce the stress response (153). The practice o f yoga produces a
physiological state opposite to that of the flight-or-fight stress response (24). It interrupts
the stress response to create a sense of balance and union between the mind and body
(155). Mental health problems such as depression, anxiety, stress, and insomnia are
among the most common reasons for individuals to seek treatment with complementary
therapies such as yoga (117). Yoga encourages one to relax, slow the breath, and focus on
the present moment. It shifts a balance from the sympathetic nervous systems to the
21
parasympathetic nervous systems. The precise mechanism by which yoga causes this
shift has yet to be determined but it has been hypothesized to be via direct vagal
stimulation (65). By regular practice o f the relaxation (parasympathetic) response it
increases individual’s resilience to stress (36). Poses that twist and compress organs help
message and rejuvenate immune organs and channels by generating balanced energy that
is vital energy for the immune system (6). Yoga has been shown to increase blood flow to
the intestines and vital organs, therefore increasing levels of hemoglobin and red blood
cells which allows for more oxygen to reach body cells thus enhancing their functions
(155). Studies have shown significant decreases in breathing, heart rate, and blood
pressure suggesting that yoga has an immediate quieting effect on the HPA axis response
to stress (89, 134). An eight-week study on yoga found psychological benefits in mildly
depressed patients by inducing an immediate effect on cortisol levels indicating a direct
effect on the HPA axis (100).
Yoga has been shown to have an immediate effect on decreasing anxiety (100,
123, 151) and increasing feelings of emotional, social, and spiritual well-being (102). A
study on college students and the effects o f yoga found reductions in anxiety and
irritability scores, improvements in concentration, self-confidence, attentiveness, and an
optimistic outlook following yoga practice, suggesting that yoga can be beneficial in
achieving a tranquil state of mind during routine activities (84). This study also indicated
improvements in concentration and arousal that was essential in demanding or stressful
situations like examinations. The researchers emphasized that in challenging situations a
22
certain element of anxiety is beneficial because individuals perform best under optimal
stress but with any additional stress, performance deteriorates. Findings have suggested
that yoga produces these beneficial effects by the inhibition of the posterior or
sympathetic area of the hypothalamus (155). This inhibition optimizes the sympathetic
responses to stressful stimuli and restores autonomic function regulatory reflex
mechanism associated with stress (155). It reduces the areas responsible for fear,
aggression, and rage, and stimulates the rewarding pleasure centers o f the brain leading to
bliss and pleasure. Studies have shown that this inhibition results in lower anxiety, heart
rate, respiratory rate, blood pressure, and cardiac output in students practicing yoga and
meditation (10, 16, 41). Yoga further improves cardiovascular efficacy and homeostatic
control of the body and results in improved autonomic balance, respiratory performance,
psychological profile, and overall well-being (16).
Yoga practice has been shown to reduce the impact o f the exaggerated stress
responses associated with anxiety and depression by the down regulation of the HPA axis
(135). The HPA axis generally triggers as a response to physical or psychological
demands, leading to a cascade of physiological, behavioral, and psychological effects
(25). This response leads to the mobilization of energy needed to combat the stressor
through the classic fight-or-flight response (135). Over time, the constant state o f
alertness, resulting from repeated firing of the HPA axis, can lead to dysregulation o f the
immune system and ultimately lead to various diseases and disorders (94, 132).
23
It appears that yoga reduces perceived stress and anxiety by adapting the stress
response systems which in turn decreases physiological arousal and increases HRV (135).
This response demonstrates the body’s ability to be more flexible in response to stress. A
study evaluating the effects of fifteen minutes of stretching in Hatha yoga over fourweeks found a significant increase in HRV and a marked decrease in heart rate (100).
This study determined that increased flexibility correlated with improvements of cardiac
autonomic function. A German study published in 2005 analyzed individuals over weekly
(90 minute) yoga classes for three months, and found (based on self-reports)
improvements in perceived stress, depression (50%), anxiety (30%), energy, fatigue, and
well-being (65%), indicating a substantial effect of the yoga class on psychological
outcomes (123).
A growing body of evidence supports the belief that yoga benefits physical and
mental health via down-regulation o f the HPA axis and SAM axis (74, 123). Brief yogabased relaxation training normalizes the function of the autonomic nervous system by
moving both the sympathetic and parasympathetic indices toward a more normal region
(117). Yoga postures (asanas) are low intensity usually non-strenuous exercises which
affect the HPA axis positively by bringing down sympathetic stimulation and
significantly decreasing the release of catecholamine’s (74). Yoga practice may inhibit
the activity o f the paraventricular nucleus o f the hypothalamus, which in turn affects the
anterior pituitary gland to produce less ACTH (6). A decrease in ACTH decreases the
synthesis of cortisol by the adrenal gland (72). Cortisol activates the enzyme
24
phenylethanolemine N-methyltransferase (PNMT), which converts norepinephrine to
epinephrine (9). With a decrease in cortisol it consequently inhibits sympathetic tone and
a decrease in catecholamine formation (6). Decreased levels of corticosteroids and
catecholamine’s are known to therefore decrease the stress response (6). It is thought that
reduced sympathetic activity and improved parasympathetic drive the normalization of
the HPA axis (20).
Although a clear mechanism o f change has yet to be identified or empirically
supported on a consistent basis, the slow and deep breathing exercises involved in
meditation are thought to alleviate bodily symptoms of distress by balancing the
sympathetic and parasympathetic nervous system responses, thereby modifying cardiac
ventricular activity (37). Meditation has been seen to affect the autonomic nervous
system which controls and regulates the overall feeling state o f the body through its two
systems, the sympathetic and parasympathetic. The sympathetic system activates the
body and releases stored energy; and the parasympathetic governs the relaxation,
recuperation, and digestive system of the body (63). Meditation involves the intentional
and repeated practice of deliberately activating the body’s relaxation response
(parasympathetic), which then counteracts the sympathetic response allowing one to
manage stress in an appropriate manner (48).
Among various approaches to reduce the levels of anxiety or depression, yoga is
one that combines the physical elements of a healthy lifestyle with prescriptions for
abiding mental peace (57). Although the mechanism that mediates the therapeutic
25
benefits of yoga has yet to be clarified specifically, it has been suggested that yoga-based
guided relaxation helps in the reduction o f sympathetic activity through the reduction in
heart rate, oxygen consumption, and increase in breath volume, which are the clinical
signs of neurohormonal activity, thus facilitating in the protection effect (135). By
managing stress, especially chronic or long-term stress, through the practice o f various
relaxation techniques it may help individuals overcome other co-morbidities associated
with disease and lead to a better quality of life even during periods of stress (6).
Aerobic Exercise
Aerobic exercises, such as running, swimming, and dance, involve prolonged
activity of large muscle groups. In many studies aerobic exercise is defined by physical
exercise implying a regular, structured, leisure-time pursuit (128). Although aerobic
exercise may be demanding and exhausting, individuals have stated that they feel good
after completing the exercise (91). Aerobic exercise is a complex psychobiological
stimulus, meaning that repeated exposure to uncontrollable stressors causes the body to
eventually become resistant to stress, but with exposure to controllable stress this can be
achieved more quickly (83). Aerobic exercise is considered a controllable stressor that
challenges homeostasis by stimulating the sympathetic nervous system to release
adrenaline and noradrenaline (45). It produces many o f the same bodily sensations that
often elicit anxiety reactions such as an increase in heart rate, respiration, and
perspiration (17). It has been suggested that mild repeated stressors may be health
promoting by affecting neural networks that are shaped by prior experience, resulting in
26
altered regulations in response to future stress (125). Researchers believe that by
repeated exposure to anxiety related interceptive stimuli, through exercise, may therefore
eliminate the fear response (17).
Benefits o f aerobic exercise
Although exercise is regarded, in most research, as a purely physiological
stimulus its emotional effects depend intimately on social and other environmental cues
as well as the expectations of the individual (15, 98). A typical duration o f training
programs in psychological literature is around 10-12 weeks, reflecting the minimum
period necessary for positive effects (128). Evidence that physical activity is enjoyable
emerged when mood was measured immediately before and after exercise, and was
related to lower perceived stress in day-to-day life (140). Cross-sectional studies have
consistently demonstrated the association between high levels of physical activity and
better mental health. Steptoe et al. (1997) found, based on self-reported measures of
16,483 undergraduate students, exercise correlated with lower depression rates (139). A
similar study based on self-reported measures o f 55,000 individuals found a correlation
between recreational activity and better mental health, including fewer symptoms of both
anxiety and depression (138). Longitudinal surveys have further confirmed definitively
that exercise habits do predict later freedom o f stress, anxiety, and depression. A study
performed on 4,848 individuals found that an absence o f exercise habits was linked to
depression later in life across two successive nine-year periods (22). Stewart et al. (1994)
evaluated self-reported measures based on 1,758 participants and found that exercise
27
predicted a range of positive health outcomes two years later, including, well-being and
lower levels of anxiety, depression, and fatigue (141). These positive effects have even
been seen to last up to 25 years based on a study performed by Paffenbarger et al. (1994)
(110). This suggests the possible long-term psychosocial effects associated with aerobic
%
exercise that serves to relieve depression and anxiety (91).
Meta-analyses of a variety o f studies have estimated that depression scores
decrease by between 0.3 to 1.3 of a standard deviation after exercise training in
comparison with a variety of control conditions (35, 107), and have also indicated an
anxiolytic effect with aerobic exercise training (80, 92, 116). Depression is associated
with low levels of norepinephrine, therefore it has been suggested that aerobic exercise
may facilitate in the production of that neurotransmitter substance and thereby relieve
depression (91). McCann et al. (1984) performed a 10-week study on the effects of
aerobic exercise on depression and found that the running group showed greater
reductions in depressive symptoms when compared to the no treatment group (91).
Similarly, Brown et al. (1979) assessed depression in subjects that were placed in a
jogging or control group, and found a reliably greater decline in depression in the jogging
group (19). Aerobic exercise is associated in reduced generalized arousal of anxiety
sensitivity, including heart rate and muscle tension (1). Anxiety sensitivity is described as
an enduring fear o f anxiety and anxiety related sensations brought about from the belief
that these sensations can have harmful physical, psychological, or social consequences
(119). A non-experimental study found an inverse relationship between exercise
28
frequency and anxiety sensitivity (96). The researchers suggested a possible explanation
for this effect to be due to the fact that exercise produces physiological sensations similar
to those feared by individuals with high anxiety sensitivity and it is therefore avoided by
participation in exercise (96). Alternatively, the lack of exposure to these sensations,
resulting from physical inactivity, promotes anxiety sensitivity (17).
Literature assumes that because exercise training reduces the cardiovascular
response to physical stress by improving individual’s fitness level, that it should have a
similar effect in psychological stress (128). Research has shown that exercise that is more
intense than that of the participant’s habitual level is less likely to improve mood and is
liable to worsen the symptoms (156). It has been indicated that anxious mood is reduced
by mild exercise training, which is insufficient to increase fitness level; whereas training
that is sufficiently intense improves fitness level but is less effective at relieving anxiety
(103). Furthermore, in studies by Roth and Homes (1987) and McCann and Homes
(1984), depression declined within five weeks of training before fitness measures had
even changed (91, 124). Overall, these findings suggest that cardiovascular responses do
not correlate with mood changes. Conversely, a study by Broman et al. (2004) analyzed
the beneficial effects between high and low intensity exercise and found that although
both types were successful on average at decreasing overall anxiety sensitivity, the high
intensity exercise produced a more rapid reduction over a two-week period (17). Results
may have been influenced by the environment o f the activity such as social engagement
in group based exercise. An increase in social activity is likely to have been a critical
29
feature of exercise. A growing body of evidence has indicated that aerobic exercise is an
effective, accessible, cost-efficient, behavioral manipulation that acts to alleviate
symptoms and reduce the occurrence of stress-related mood disorders (56). Overall, it has
been shown that aerobic exercise is an ideal treatment alternative for a variety of anxiety
and mood disorders.
It is now well accepted that habitual physical activity significantly reduces the
incidence and severity of stress-related mood disorders, such as depression and anxiety
(56). It is believed that physical exercise training produces a protective element from the
harmful effects o f stress and the resulting loss of the protective benefits of exercise could
further intensify the response to major stressors (128). Diverse explanations have been
proposed for the psychological effects of exercise training. It has been suggested to be
due to changes in body temperature or cerebral blood flow, improvement in self-esteem,
distractions from negative thoughts, or improved retrieval of positive thoughts (42). The
protective effect of exercise against depression or anxiety are large, in fact it is equal to
that o f the well known protective effect of exercise against cardiovascular disease (107).
Although evidence suggests that exercise can prevent the development of depression and
anxiety, the underlying mechanism o f this effect remains unsolved (56). Many studies
have indicated that after exercise, blood pressure falls below pre-exercise levels (59, 118,
120) and heart rate stays elevated for hours after exercise (46, 73). The mechanism
underlying post-exercise hypotension remains controversial (143). It is proposed that
after aerobic exercise, the increase in heart rate during the recovery period has been
30
attributed to a persistent increase in sympathetic modulation and a decrease in
parasympathetic modulation to the heart (60). Despite its well-proven acute hypotensive
effect (low blood pressure), evidence is mixed as to whether cardiovascular or
sympathoadrenal responses to psychological stress are reduced by exercise (128).
Endurance training leads to cardiovascular, metabolic, and hormonal adaptations
to ensure that there is minimal homeostatic disruption during exercise (150). The HPA
axis is both stimulated by exercise and subjected to adaptation with exercise training by
influencing CRH, ACTH, and corticosterone (109,114). Further indication of the adaptive
response of the HPA axis via autonomic activity has been shown by analyzing the HRV
effects during exercise (87). Surprisingly, changes in HF and LF powers and the LF/HF
ratio observed during exercise have not been shown to decrease vagal activity with
increasing the level of intensity (114). One o f the first studies on HRV during exercise
expected that HF would progressively decrease with intensity indicating a decrease in
parasympathetic activity and LF activity would increase implying sympathetic
dominance (114). In contrast, HF power was substantially unchanged from rest up to
70% V02Max and LF power significantly decreased at medium-high intensity. Even with
these results, the LF/HF ratio clearly indicated sympathetic dominance occurred in
autonomic interaction, which is to be expected because exercise produces the stress
response (114). Another study analyzed eight-weeks of aerobic training and found that it
induced an increase in VO 2 peak, a decrease in resting heart rate and arterial pressure,
with no change in HRV parameter in elderly subjects (114). This evidence suggested that
31
HRV does not appear to be increased in a dose-dependent manner with increasing levels
of physical activity leading to a different outcome than researchers would have expected
(97). These findings may underlie the protective and adaptive effects of exercise training
on the hyper-responsiveness of the HPA axis to behavioral stress (87).
Yoga versus Aerobic Exercise
Aerobic exercise, such as running, involves the prolonged activity of large muscle
groups; while anaerobic exercise, such as yoga, involves more intense, brief, and non­
sustained movements (128). Yoga, although not entirely risk free, can be considered a
safe form of exercise if practiced under the guidance and supervision of a qualified
trainer (135). Evidence is growing that yoga practice is a low-risk, high-yield approach to
improving overall health. The usual measure of fitness in psychological research has
been in aerobic exercise (128). The practice of yoga has now been shown to improve
mood in a way comparable to aerobic exercise (70). Over the years non-strenuous
procedures, such as relaxation and flexibility training, have been designed to be
comparable with exercise for skill mastery, distraction from normal activities, or social
interaction (128). Studies comparing the effects of yoga and conventional exercise seem
to indicate that yoga may be as effective as, if not even better than exercise at improving
a variety o f health related outcomes (117). For many individuals dealing with stress yoga
may be a very appealing way to better manage symptoms (135).
32
Meditation and relaxation techniques have produced similar improvements in
self-rated depression as compared to exercise training (78). Moderately-intense aerobic
exercise and low-intensity yoga are well known to lower blood pressure, the mechanism
by which they induce blood pressure reductions may be attributed to their beneficial
effects on the autonomic neurological function (135). While aerobic exercise has been
shown to improve parameters o f fitness, yoga has improved fitness levels in strength,
endurance, flexibility, and VChmax (145). Yoga techniques are known to improve overall
performance and work capacity (137). Evidence has suggested that yoga interventions
appear to be equal and/or superior to exercise in nearly every outcome measured (123).
In two well-controlled studies looking at the reduction o f depressive symptoms,
over 11 weeks o f aerobic training in comparison with relaxation, strength, and flexibility,
found a similar correlation between both types of exercise in reducing symptoms (124,
140). During a follow-up period the effects were maintained at three months. Chattha et
al. (2008) compared the effects of 8 weeks o f daily yoga to walking exercises, and found
that the yoga group exhibited significant improvements in psychological, somatic, and
vasometer, while the exercise group improved significantly only in the psychological
factor (26). The yoga group also exhibited a significantly greater decrease in levels of
stress. A similar study compared 4 months of daily yoga to exercise, and found that both
groups exhibited significant reductions in psychotic symptoms but the yoga group
improved significantly better (47). A study looking at the short term effects o f a single
yoga class versus an aerobic dance class, found that the yoga group experienced
33
significant reductions in salivary cortisol while the dance class had a significant increase
in salivary cortisol level (151). These findings indicate that yoga and exercise may both
improve mood but affect the HPA axis differently (123).
Two studies have compared yoga with aerobic exercise in HRV response. Khattab
et al. (2007) compared HRV during a 60-min yoga class versus 60-minutes walking, and
found that yoga exhibited greater HRV particularly in the measures associated with
parasympathetic tone (75). A 6 week, randomized control trial, was performed based on
the belief that exercise and yoga exert different effects on the sympathetic nervous
system (14). Researchers discovered that HRV remained unchanged in the cycling group
while there were significant changes in the yoga group. A change in the HRV by the yoga
practice supports the notion that yoga acts on the sympathetic nervous system by
increasing parasympathetic arousal (14).
Differences between yoga and aerobic exercise may be a result o f how the two
differ in their effects upon the HPA axis (123). Low-intensity exercises have repeatedly
been shown to lower cortisol levels (38, 52), while high intensity exercise leads to
proportional increases in cortisol (64). Perhaps this is why yoga, involving slow and often
non-strenuous activity positively affects the HPA axis response to stress by lowering
sympathetic stimulation, therefore lowering levels of norepinephrine and epinephrine
(134). Aerobic exercise, on the other hand, appears to stimulate the sympathetic nervous
system, therefore raising plasma epinephrine and norepinephrine (13, 115). It is possible
that yoga might not only be an acceptable addition to care, but an effective, feasible, and
34
accepted alternative to exercise (123). Similarly to exercise, yoga has advantages in that
it is cost-effective, non-invasive, has minimal risk of adverse effects or drug interactions,
does not require medical supervision for practice, and has added benefits o f improving
physical fitness (37).
Study Rationale, Purpose, and Hypotheses
Stress is a major issue for college students as they struggle to balance a variety of
academic, personal, and social pressures. The increase in stressful life events in college
students has been associated with anxiety and depression (39). Research on college
students supports the relationship between heightened levels o f stress that alter behavioral
patterns leading to a compromised health (104, 127). Given the fact that clear evidence
exists regarding the efficacy o f both aerobic exercise and yoga interventions in alleviating
various symptoms and improving outcomes, it is surprising that researchers have not
discriminated more clearly between the effects o f the two on improving mental well­
being.
The purpose of this study was to evaluate and compare yoga and aerobic exercise in
its effects of promoting mental well-being in college students. This study will specifically
compare mental well-being and autonomic nervous system function in college students
enrolled in yoga and aerobic activity type course. It is hypothesized that the students
engaged in the yoga course will experience improved well-being and the individuals who
participate in the activity for longer periods o f time will experience mental well-being.
35
METHODS
Participants:
The participants were recruited from activity courses at San Francisco State
University, during the fall 2014 semester. There were a total o f 334 subjects
(aerobic=T86, yoga=148) that participated. Thirty-four individuals (aerobic=18,
yoga=14) were randomly selected from the large pool of individuals to have
physiological measures performed. Two of the individuals were excluded from the study
due to abnormal heart rhythms. Individuals were selected based off of indicated interest.
All participants were 18 or older, and had no major health conditions that would impair
their ability to participate in each of the exercise courses. All participants read and
acknowledged the risks, both physical and mental involved in their participation in
exercises courses on the San Francisco State University campus.
Inclusion/Exclusion Criteria:
All participants had to be enrolled in one of the selected activity courses at San
Francisco State University in order to participate in the study. They were excluded if they
had any current health conditions that could put them at a potential risk of injury with
participation in the exercise courses. Individuals selected for physiological measures
were excluded if they were currently taking anti-depressants, anti-anxiety medication,
and/or medication for ADHD because o f the drug’s effects on the autonomic system.
Procedures:
36
Participants enrolled in activity courses (KIN 100- Aerobic low impact, KIN 103Aerobic Step, KIN 139- Jogging, KIN 136- Hatha Yoga) who volunteered to participate
were separated into two groups based on the type of activity course (yoga and aerobic
exercise). In order to assess individuals’ mental well-being they were required to fill out
five self-reported questionnaires during the normal date, time, and location of the activity
course. The questionnaires given were the Penn State Worry Questionnaire, Subjective
Happiness Scale, Perceived Stress Scale, Subjective Vitality Scale, and the Mindful
Attention Awareness Scale.
In the information section, at the conclusion o f the questionnaires, there was a
question asking if the individual would be interested in participating in physiological
measures. If the individual answered “yes”, they had the potential to be randomly
selected to have two physiological measures done. Physiological measures obtained were
body composition and a 10-minute resting three-lead ECG.
Body Composition Procedure
Body composition was assessed by using a machine called the BodPod®
(Concord, CA). Individuals were instructed to wear tight fitting clothing to ensure most
accurate reading. They were placed in the machine which took approximately 5-minutes.
The variables obtained were body fat and fat-free mass percent.
Heart rate Variability Procedure
37
A 5-minute electrocardiography (ECG) tracing was obtained using the Biopac
MP150 Data Acquisition System (San Francisco, CA) while the participant rested in a
supine position. The ECG was inspected for irregular beats and if any were found they
were removed. A spectral analysis was performed using an autoregressive algorithm. The
power spectrum was analyzed for total power (TP) with a power range o f 0.0-0.4 Hz,
Low Frequency (LF) power with a power range o f 0.04- 0.15 Hz, High Frequency (HF)
power with a range of 0.15- 0.4 Hz, and the LF/HF ratio. TP is the integrated power in
the observed spectrum between the lower frequency edge and the upper frequency edge
o f the high frequency. LF is an indicator of the sympathetic system while HF is
associated with a heightened parasympathetic system. The LF/HR ration is used to assess
autonomic balance.
Statistics:
All quantitative information was analyzed using a one-way ANOVA. The
findings were found using Pearson Correlation. An Independent T-test was used to
assess all physiological measures. A significance level o f < 0.05 was used for all the tests.
RESULTS
Survey Results
The questionnaires given to analyze the overall well-being of individuals
participating in either yoga or aerobic exercise looked at levels of mindfulness, worry,
vitality, happiness, and stress. There were a total o f 334 participants, o f which 186 were
38
in the aerobic group (females=l 18, males=68) and 158 were in the yoga group
(females=l 16, males=32). When analyzing group differences in relation to the
questionnaires there were no significant differences found on activity type and better
overall well-being (Table 1, Graph 1). However, when the Pearson Correlation was
performed there was a significant difference found between increased participation in
physical activity (1.54 ± 0.82) (Table 2). This correlation was associated with decreased
levels of stress (Table 2). When putting activity type aside and assessing possible sex
differences (Table 2), the data showed that females have significantly higher scores in
stress levels than men (Graph 2).
Survey Figures and Tables:
Dependent Variable
Yoga and Aerobic
Mean
Std.
Error
95% Confidence
Interval
Lower
Bound
Upper
Bound
Aerobic
4.030
.057
3.917
4.142
Yoga
3.859
.064
3.733
3.984
Aerobic
51.251
.990
49.305
53.198
Yoga
52.229
1.106
50.054
54.404
Aerobic
4.610
.085
4.443
4.777
Yoga
4.617
.095
4.430
4.803
Aerobic
4.969
.080
4.811
5.126
Mindfulness
Worry
Vitality
Happiness
39
Yoga
5.118
.090
4.941
5.294
Aerobic
1.858
.048
1.763
1.953
Yoga
1.886
.054
1.780
1.992
Stress
Table 1. Activity type differences between questionnaires.
60
Mindfulness
Worry
Vitality
Happiness
Stress
Figure 1. Exercise type versus survey differences. Mean ± Std. Error
Activity
Level
M indfulness
Worry
Vitality
H appiness
Stress
0.005
P = 0.928
-0.039
P = 0.458
0.096
P = 0.064
0.034
P = 0.518
-0.109*
P = 0.038
Table 2. Pearson correlation between increased participation in activity and questionnaire
scores; p-value < 0.05.
40
Dependent Variable
Gender
Mean
Std.
Error
95% Confidence
Interval
Lower
Bound
Mindfulness
Worry
Vitality
Happiness
Stress
Upper
Bound
female
3.900
.052
3.798
4.002
male
4.038
.085
3.871
4.205
female
54.558
.855
52.876
56.240
male
45.347
1.402
42.588
48.105
female
4.596
.077
4.445
4.747
male
4.702
.126
4.454
4.950
female
5.057
.073
4.914
5.200
male
5.074
.119
4.839
5.308
female
1.948
.043*
1.863
2.033
male
1.681
.071
1.542
1.820
Table 3. Sex differences versus surveys.
41
Stress
2.05
■Female
■Male
Female
Male
Figure 2. Difference between sex and stress levels.
Physiological Measures Results
In order to assess changes within the body associated with activity type
individual’s heart rate variability was analyzed. Table 4 shows the participants’
descriptive information obtained for physiological measures. There were a total of thirtytwo individuals (aerobic=18, yoga=14) included in the physiological testing, of those
twenty -one were female and eleven were male. There were no group differences
between groups within the descriptive information. Table 5 summarizes all the Heart
Rate Variability Indices between groups and is depicted within figures 3,4,5, and 6. There
were no significant differences found in heart rate variability between groups.
Physiological Measures Figures and Tables:
Group
Age
% Fat Free Mass
% Body Fat
42
Aerobic
22.83 ± 0 .9 7
76.84 ± 2 .4 0
23.16± 2.40
Yoga
22.00 ± 0 .9 3
73.88 ± 2 .4 5
8.45 ±0.64
Table 4. Descriptive information. Data are mean ±SD.
InLF
InHF
Aerobic
8.26 ±0.42
9.10 ±0.76
Yoga
8.45 ±0.64
8.97 ±1.06
Group
LF-HF
R-R
SDNN
9.96 ±
0.62
0.97 ±0.62
968.23 ±
47.62
94.22 ±
9.97
10.04
±0.88
2.57 ±0.98
901.84±
23.55
85.95 ±
13.98
InTP
Table 5. Heart Rate Variability Indices. Data are mean ± Standard Error.
10
9.5
Aerobic
Yoga
Figure 3. High Frequency (HF) power between exercise type.
10
9.5
(N
c /i
£
U«
J
c
7.5
7
Aerobic
Figure 4. Low Frequency (LF) power between exercise type.
Aerobic
Figure 5. Total power between exercise type.
44
10
-
8
Aerobic
Yoga
Figure 6. LF/HF ratio between exercise type.
DISCUSSION
Based off the questionnaires given, there were no differences found between type
o f physical activity and a heightened state o f well-being. However, there was a
significant correlation between increased participation in physical activity and decreased
levels of stress (20, 30). Prior research has stated that although both forms of exercise
improve psychological well-being, yoga has been found to have a significantly greater
decrease in stress levels (29, 55). Psychological research has shown that the minimum
period necessary for positive effects is between 10-12 weeks (69, 128). Interestingly, the
current research indicated that females had significantly higher stress levels than men. A
study looking at stress on first-year undergraduate students in Australia (112) found that
52.9% of students were suffering from some degree o f stress but with significantly more
45
female students than males which has similarly been observed on undergrads in Hong
Cong (154) and Turkey (8). Across nations and cultures, women of reproductive age are
approximately two times more likely to suffer from stress related symptoms than men
(105). Although the exact mechanism has yet to be determined, it is thought that there
may be sex differences associated in the HPA responses to stress effecting coping
behavior (142). It is also thought that social roles may play a part in increased levels o f
stress for females (88).
Overall the physiological measures that assessed heart rate variability had no
significant differences between groups within all indices, meaning there were no
differences between groups in autonomic control. The aerobic group had a slightly lower
LF/HF ratio when compared to the yoga group, indicating a heightened parasympathetic
activity, although this difference was not considered significant. Studies performed by
Khattab et al. (2007) and Bowman et al.(1997), found greater HRV in yoga individuals
particularly in measures associated with parasympathetic tone (16, 100). Both groups had
similar heart rates indicative of healthy individuals (Aerobic: 968.2 ms= 62 bpm; Yoga:
901.8 ms= 66.5 bpm) which is to be expected for individuals who are physically active.
In conclusion, individuals who have been participating in physical activity for
longer periods of time tend to have lower levels of stress. This may suggest that physical
activity acts as a protective mechanism for the prevention o f stress related disorders, such
as anxiety and depression that are highly prevalent in college students.
46
Study Limitations
The current study had a few limitations that could have affected the results. The
yoga class met once weekly while the aerobic class met twice weekly. This may have had
an effect on the lack of differences between groups. The data was collected after students
had been participating in the course for 8-10 weeks which could explain the lack of
changes in the physiological and psychological parameters. The study also included a
wide range of activity levels from low to high fit ranges based off how long they had
been performing that particular activity. Individuals may have also been participating in
other forms o f exercise throughout testing.
FUTURE RESEARCH
Future clinical trials are needed to further examine the distinctions between
aerobic exercise and yoga, particularly on how the two modalities may differ in the
effects on the HPA axis (123). There are several types/different styles of yoga, each with
distinctive challenges and varying levels o f difficulty. Each style differs in the emphasis
placed on the various components o f yoga. It has been suggested that future studies
analyze the relative effects o f these different types of yoga on the HPA axis with acute
and chronic stress (123). It has also been recommended that future research identify
which form of yoga-based intervention is most effective and what level o f severity of
depression or anxiety are likely to respond the best. There is also a need for more
47
comparisons studies on the effectiveness of aerobic and anaerobic exercise on short-term
and long-term psychological effects (117).
48
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