A very good review of recent yoga research findings

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From

JOY: The Journal of Yoga October 2003, Volume 2, Number 10

 

 

YOGA: A SCIENTIFIC LIFESTYLE

Aaarti Sood Mahajan and R. Babbar

Department of Physiology, Maulana Azad Medical College, New Delhi

 

 

Abstract

Yoga is an ancient science established in India. Those practicing

this lifestyle lead a disciplined life. There is tremendous control

on food habits, exercise, rest, breathing style and the mind. In

recent years, there has been a commercialization of yoga. Some teach

and practice it without understanding the fundamental precepts.

Scientists in India and abroad are working on different aspects and

finding scientific explanations for yogic phenomena. This review is

an attempt to consolidate and pay a tribute to their efforts. It

brings out the way yoga influences physiological functions and its'

usefulness in disease. This and other attempts in the future may

ultimately rationalize and add objectivity to the science of Yoga.

Key words: Yoga, physiology, fitness, disease, healthy lifestyle

 

Introduction

Yoga originates from the word Yuj or union. It symbolizes the union

of one's spirit with that of the divine. The process of achieving

this is methodically simple, but requires determination and self-

control. It also requires a healthy body, not only a physically fit

body. To establish this harmonious balance in physiological

processes, the yogis follow the eight progressive steps of Yama,

Niyama, Asana, Pranayama, Pratyahara, Dharana, Dhyana and Samadhi.

These techniques are ideal for the preventative, promotive, curative

and the rehabilitative aspects of health (Baride et al 1994). In this

review we look into the physiological basis of the effects of yogic

practices. This is an attempt to consolidate the effort of various

scientists to rediscover an ancient science called yoga.

 

The Disciplines of Yoga

Yoga is not a religion; it is a philosophy of life. The intellectual

follows Jnana Yoga, the way of wisdom and discernment. Karma Yoga

emphasizes selfless action and service, while Bhakti Yoga is for

those who seek god through love and devotion. Raja Yoga is for those

contemplating individuals who control the mind by concentration. It

lays emphasis on Hatha Yoga, the practice of Asanas (posture) and

Pranayama (breath control). Asanas stretch the muscles and increase

their tone. The stretching massages the organs in the local vicinity,

stimulates blood circulation and increases their secretion. Pranayama

or yogic breathing involves the use of abdominal, upper and lower

thoracic muscles in a rhythmic and coordinated manner. Breath holding

may accompany inhalation and exhalation. The idea of deep breathing

is to accumulate prana-the source of energy known to maintain the

body. Scientifically, deep slow breathing may strengthen the

respiratory muscles, increase their compliance, increase the oxygen

intake and its diffusion into the lungs, and ultimately lead to an

increase in the ventilation perfusion ratio. Increase in the oxygen

uptake may also increase metabolism. However, different types of

pranayama exist like Ujjayi, Bhastrika, Nadi Shoddhana, Sitali etc.

In Ujjayi, inhalation is via the nostrils and exhalation is through a

half closed glottis producing a low continuous sound. Nadi Shoddhana

involves alternate nostril breathing generally accompanied by breath

holding in a rhythm. In surya Bhedana the person inhales through the

right nostril and exhales through the left nostril. In sitali

inhalation is through the mouth with the tongue rolled to produce

a " sss " sound and exhalation is through the nose. Bhastrika involves

the rapid movements of abdominal muscles.

Additional Yogas include Kundalini Yoga, Dhyana Yoga, Mantra Yoga,

Laya Yoga, Shanti Yoga, Mudra Yoga and Yantra Yoga (Iyengar, 1995).

However, the complete description of yogic practices is beyond the

scope of this review.

 

 

The Physiological Concept

Yogic procedures maintain normal body functions. They affect higher

functions of the central nervous system (C.N.S) like perception,

planning, execution of tasks, learning and memory. Yoga with breath

control techniques increases the cerebral blood flow (Reader 1993).

Meditation or Dhyana trains the mind to concentrate on an inner or

outer object, channelises the thoughts in an attempt to get beyond

mental distractions. It improves coherence between the two cerebral

hemispheres signifying synchronization of logical and intuitive

function. It increases alertness, along with relaxation. Alertness

decreases the reaction time of the brain. Twelve weeks of yoga is

known to decrease the visual and auditory reaction times (Telles et

al 1995; Uma et al 1989). Pranayama alone and Mukh bhastrika have

shown similar effects (Borkar and Pednekar 2003; Ananda Balayogi

Bhavanani et al 2003). Similarly, planning and execution of any task,

thought to be a frontal lobe function is enhanced. Yoga accompanied

with meditation for a month has shown decreases in time required to

perform certain tasks (Manjunath and Telles 2001). Spatial tasks are

enhanced during left nostril breathing and verbal tasks during right

nostril breathing. Breathing through a particular nostril also

improves spatial memory scores (Naveen et al 1997). Perception of any

geometrical illusion is influenced by retinal, cortical and cognitive

judgmental factors. A decrease was observed following practice of

focusing and defocusing (Telles et al 1997; Vani et al 1997).

Similarly, the process of learning involves selection, choosing,

decision-making and other higher brain functions. However, maze

learning may improve due to repeated performance rather than yoga

alone (Telles et al 2000a). The ability to perform rapid fractionated

movements depends upon monosynaptic connections between the cortex

and the ventral horn cells of the spinal cord. Dexterous or skilled

actions depend upon speed of gross movement of the hand and arms

steadiness, rhythm, coordination of eyes and motor control. This was

seen to improve after yoga. Presumably, a reduction in anxiety can

account for these benefits (Telles et al 1994; Manjunath and Telles

1999). Nevertheless, higher functions of the CNS are augmented by a

yogic lifestyle.

The body is ultimately controlled by the CNS through its relationship

with the autonomic nervous system (ANS) and the neuroendocrine

processes. Yogic processes have a tremendous influence on the central

nervous system. It helps an individual to gain control over the ANS

resulting in homeostatic functioning of the body. However, there is

no definite model of sympathetic activation or relaxation during

practice of meditation and there can be individual variations (Telles

and Desiraju 1993a). Selvamurthy et al found that six months of yoga

resulted in an autonomic shift towards the parasympathetic nervous

system. Sirsasana is associated with increased sympathetic activity

while Shavasana brings about a reduction in the sympathetic response

(Manjunath and Telles 2003; Madanmohan et al 2002). Yogic breathing

exercises include right and left nostril breathing. These breathing

techniques stimulate different divisions of the ANS, thus having

useful implications in treating psycho physiological disorders

associated with hemispheric and autonomic imbalance (Jella 1993;

Shannahoff 1991). Right nostril breathing correlates with the

activity phase of the basic rest activity cycle, it activates the

sympathetic nervous system as shown by an increase in the oxygen

consumption and left nostril breathing decreased the sympathetic

activity as manifested by an increase in the level of volar galvanic

skin resistance (Werntz et al 1983; Telles et al 1996).

Studies of EEG and evoked potential have indicated that there is

increase in cortical activity along with synchronization. Marked

uniformity of frequency, amplitude and electrical activity was

observed in all areas of the brain (Khare and Nigam 2000). Nostril

rhythm increases the theta rhythm, the mean alpha (a) and beta (b)

power followed by reduction in the asymmetry in b band in the EEG

(Stancak and Kuna 1994; Stancak et al 1996; Wallace et al 1971).

Practice of Santhi kriya has shown to increase the a activity in both

the occipital and prefrontal area (Satyanarayana et al 1992), while

an increase in b activity is reported in those practicing Sudarshan

Kriya for a long time (Bhatia et al 2003). Six months of Sahaj Yoga

decreases the seizure frequency in patients of epilepsy. Stress

reduction is suggested as a probable cause of benefit (Panjwani et al

1995, 1996).

Meditation with the thought focused on the syllable " OM " showed an

increase in amplitude with a reduction in latency of middle latency

auditory evoked potentials (AEP) (Telles and Desiraju 1993b, Telles

et al 1994). Pranayama exercise of Ujjayi and Bhastrika also

increased the amplitude and decreased the latency of Na wave of

middle latency AEP, indicating facilitation of processes of sensory

signal transmission. These practices involve the use of various

cortical mechanisms and corticofugal control processes that may alter

the process of information processing at the level of the brain stem

(Telles et al 1992). Similarly in epileptics, improvement in AEP,

visual contrast sensitivity has also been observed (Panjwani et al

2000). Yoga thus increases CNS activity, synchronization, improves

sensory processing and balances the ANS.

 

Yoga and Physical Fitness

Yoga is not restricted to any particular age group. It is therapeutic

for patients but it is also practiced in normal individuals to keep

physically fit. A study reporting increased physical fitness in

school children practicing yoga has been reported (Gharote 2000). It

is thus advisable to start early. Yoga also slows down ageing as

shown by a decrease in the reduction of baroreflex sensitivity with

age in subjects who were practicing yoga for five years (Bharshankar

et al 2003). Yogic asanas are isometric exercises that involve a

coordinated action of synergic and antagonist muscles in bringing

about steadiness, flexibility and accuracy of movement. Improvement

is seen in static motor performance, hand-eye coordination, grip

strength, cardiovascular endurance, anaerobic power, thermoregulatory

efficiency, and orthostatic tolerance. The practice of Yoga for six

months to one year improves performance by increasing stretch

duration, endurance and decreasing the onset of fatigue (Telles et al

1993a,1994; Dash and Telles 2001; Raghuraj et al 1997).

The mechanisms of yogic breathing may involve improvement in oxygen

consumption with better oxygen delivery, utilization and minimal

energy expenditure as seen in subjects who practiced pranayama. A

higher work rate with reduced oxygen consumption per unit of work

without increase in blood lactate levels is reported (Raju et al

1994). There is an accompanied increase in peripheral blood flow,

along with a decrease in body weight (Selvamurthy et al 1983;

Satyanarayana et al 1992; Telles and Desiraju 1992a; Bera and

Rajapurkar 1993; Ray et al 1986). Regular and continuous use of any

muscle prevents fat deposition, increases flexibility and heightens

performance. Ujjayi with long and short kumbhak (breath holding) may

exert their effects by alterations in the skeletal muscle activity,

ANS discharge, and cerebral blood flow. Breath holding with a short

kumbhak increases oxygen consumption, while a long kumbhak during

Ujjayi decreases oxygen consumption, and metabolic rate (Telles and

Desiraju 1991). Siddhasana is also known to increase oxygen

consumption, and metabolic rate compared to shavasana (Rai et al

1994). Virasana likewise induces a hyper metabolic state temporarily

characterized by increased ventilation, and enhanced sympathetic

activity. This gets neutralized on assuming a shavasana posture (Rai

and Ram 1993a). Yoga can improve exercise performance by increasing

flexibility, psychological motivation and decreasing heart rate,

minute ventilation, oxygen consumption/unit work and respiratory

quotient (Ray et al 2001; Raju et al 1997). Above all, yoga increases

the subjective well-being in subjects (Malathi et al 2000).

 

Yoga and Biochemical Changes

The benefits of yoga are accompanied by biochemical changes. After

three months of yoga, a significant increase in the level of

creatinine phosphokinase and decrease in pyruvate to lactate ratio

indicating increased muscular activity with anaerobic metabolism was

noted (Sahay et al 1982). A decrease in lactate, catecholamine,

dopamine beta hydroxylase, cholinesterase, monoamine oxidase, and

cholesterol has been reported. A similar reduction in blood glucose,

cholesterol, dopamine beta hydroxylase, monoamine oxidase, and

increase in urinary ketoteriods has been reported in sports teachers

after three months of training (Telles et al 1993b; Delmonte1985;

Udupa et al 1975). Three months of Kriyas, yoga and a vegetarian diet

decreases urinary excretion of adrenaline, nor adrenaline, dopamine,

aldosterone, and serum testosterone and leutenising hormone. Cortisol

levels decrease in blood along with increased excretion (Kamei et al

2000; Schmidt et al 1997). The biochemical changes indicate a hypo

metabolic state (Selvamurthy et al 1983; Wallace et al 1971; Rai and

Ram 1993b). Regional glucose metabolism in the CNS is altered during

meditative relaxation (Herzog et al 1990). Improvement in glucose

homeostasis, with reduction in fasting blood sugar, hyperglycemia,

glycosylated hemoglobin, and dose of oral hypoglycemic drugs required

after 6, and 12 weeks of yoga in Non Insulin Dependant Diabetes

patients (NIDDM) has been observed (Monro et al 1992; Jain et al

1993). The changes are suggestive of decrease in stress, sympathetic

activity, better glucose utilization and exercise tolerance.

Yoga and Hormonal Balance

The glandular activity is increased and hormonal profile is balanced.

There is a decrease in cortisol, growth hormone, and thyroxin. On the

other hand, prolactin levels increased with no change/ decrease in

catecholamine. There may be notable difference in the effect of

different types of asanas and exercises. Suryanamaskar influences the

skeletal muscle with less influence on the vital organs. Yogic

practices increase the protein bound iodine (PBI); improve the

thyroid and adrenocorticoid functions. Sarvangasana rehabitates the

thyroid gland (Delmonte 1985; Udupa et al 1975). Ujjayi with long and

short kumbhak effects adrenomedullary secretions (Telles and Desiraju

1991). Melatonin production believed to be psycho-sensitive, may

bring about the psychological benefits of yoga therapy in stress

management (Massion et al 1995).

 

Yoga and Psychiatric Disorders

The ability of yoga to bring about a reduction in sympathetic

activity is the basis of its use in stress management. Sahaj Yoga

practiced for six months was able to increase galvanic skin

resistance (GSR), indicating a reduction in sympathetic activity.

There was a reduction in blood lactate and VMA activity (Panjwani et

al 1995). A range of conditions where yoga is beneficial in

psychiatric problems has been identified (Vahia et al 1996). Subjects

of obsessive compulsive disorder have shown improvement in Yale/Brown

obsessive-compulsive scale and perceived stress scale (Shannahoff

1996). Sudarshan Kriya yoga has been used in depression and

melancholia (Janakiramaiah et al 2000). A thirty minute session of

yogic stretching and breathing exercises produced marked augmentation

in perception of physical and mental energy. It increases the feeling

of alertness and enthusiasm. It is more invigorating than relaxation

or visualization techniques especially when practiced in a group

setting (Wood 1993). Reduction in symptoms of perceived stress in

psychosomatic disorders like peptic ulcer and hypertension is noted

with immediate improvement, while patients with anxiety had a delayed

response. The response improved with the duration of treatment (Sethi

et al 1982). Similarly, in normal male volunteers a decreased

neurotism index, lowered mental fatigability, lowered incidence of

subjective complains, and increased performance quotient was observed

by scientists. Practice of yoga makes a person psychologically stable

and mentally more composed. A decreased neuro humoral responsiveness

and decreased neuroticism may be responsible for curtailing the

incidence of complaints (Udupa et al 1973). Yoga relaxation

techniques involving disengement enhances coping skills (Khasky and

Smith 1999). However, coping with specific health problems may

require specialized training (Kroner-Herwig et al 1995).

In addition to psychological and psychiatric disorders, yoga has

shown beneficial effects as a therapeutic tool for mentally retarded

children with an improvement in intelligent quotient (IQ) and social

adaptation parameters after one year of integrated therapy (Uma et al

1989). An optimal level of stress is beneficial because it can

improve performance. Yogic practices reduce anxiety and may help the

individual to cope with different types of stressors. A sense of well-

being, a relaxed mind, improved concentration, attention, memory, and

mental efficiency is seen following the practice of yoga. The results

indicate a tranquil state of mind during routine activities,

accompanied by increased attention during stressful situations

(Malathi and Damodaran 1999). It also improves the general well-being

of an individual and strengthens mental resolve. This forms the

rationale of its use in prisoners and children of broken homes

(Telles and Naveen 1997). However, it has not proven to be of more

value than psychotherapy in drug addicts (Shaffer et al 1997).

 

Yoga and Cardiovascular Response

The cardiovascular system is controlled by the ANS. Yogic procedures

differentially affect the ANS. Those that decrease the sympathetic

activity are useful in controlling the diastolic blood pressure in

mild to moderate hypertensives. Improvement in risk factors may

benefit patients of coronary artery disease. Some of the asanas

routinely recommended for improvement in cardiovascular function

include Halasana, Paschimottanasana, Virasana, Siddhasana, Shavasana

and nadi shodana pranayama (without breath holding). Yoga accompanied

by breath control increases cardiac output, decreases the hepatic,

renal blood flow and increases cerebral blood flow in the peripheral

vessels (Reader 1993). Yoga is also associated with a decrease in the

heart rate and diastolic blood pressure (BP) (Baride et al 1994).

Heart rate alterations in various types of pranayama and in single

thought and thoughtless states have been described (Telles and

Desiraju 1992 a,b). Heart rate increases in Siddhasana and Virasana

are likely due to increased metabolism (Rai et al 1994; Rai and Ram

1993b). The effects of inspiratory and expiratory phases of normal

quiet breathing, deep breathing and savitri pranayama breathing on

heart rate and mean ventricular QRS axis was investigated in young

healthy untrained subjects. Pranayama breathing produced significant

cardio acceleration and an increase in the QRS axis during the

inspiratory phase compared to eupnoea. These changes were similar to

the changes observed during the corresponding phase of deep breathing

or savitri pranayama breathing (Madanmohan et al 1986). Marked heart

rate variability (HRV), increased amplitude of oscillations as seen

during meditation indicate that it is not a quiescent state as

generally believed (Peng et al 1999).

Yoga with other regimes like muscle relaxation produces lowering of

BP that has favored its use as a non-drug therapy (Andrews et al

1982). A study has shown that yoga may be more useful than drugs, but

this has been observed in mild and moderate hypertension only

(Murugesan et al 2000). Transcendental meditation likewise resulted

in lowering of BP in borderline hypertensives. The change is

attributed either to an integrated hypothalamic response associated

with a decreased sympathetic activity or a placebo effect (Benson et

al 1974). In a study after 6 months of yoga training, exercise was

found to increase the systolic but not the diastolic BP (Gopal et al

1973).

Yoga is not only an exercise, it is a lifestyle. In a classical

paper, Dean Ornish showed that by following a lifestyle of low

vegetarian diet, cessation of smoking, stress management training and

moderate exercise, a significant number of patients had regression of

coronary artery stenosis as analyzed by quantitative coronary

angiography. It was suggested that coronary arteriosclerosis was

reversed after 1 year with comprehensive lifestyle changes without

the use of lipid lowering drugs. (Ornish et al 1990; Manchanda et al

2000). The effect of yogic lifestyle on some modifiable risk factors

has been studied in angina patients and normal subjects with risk

factors. The subjects practicing yoga showed a regular decrease in

cholesterol, triglyceride, low density lipoprotein (LDL), while the

high density lipoprotein (HDL) increased. The effect began four weeks

after treatment and continued till 14 weeks thereafter (Mahajan et al

1999).Hypertension autonomic function tests indicate attenuation of

the sympatho-adrenal and rennin-angiotensin activity. Yogic asanas

can modulate cardiovascular responses. The different types of

breathing procedures affect the ANS. Right nostril breathing

activates the sympathetic nervous system and increases the heart

rate. Alternate nostril breathing brings about a balance in the ANS

(Shannahoff 1993). Kapalabhati practice showed an increase in the low

frequency band and decrease in the high frequency band of the heart

rate variability spectrum indicating increased sympathetic activity

(Raghuraj et al 1998). Nadi Shoddhana pranayama increased both

components of HRV. Yogic asanas were found to be effective as tilt

procedures in correcting the baroreflex sensitivity in patients,

represented by the a index at high frequency, and was seen to

increase after 6 weeks of yoga indicating enhancement of

parasympathetic activity (Selvamurthy et al 1998; Bowman et al 1997).

Sarvangasana is a posture with the body inverted. It is comparable to

a negative " g " position. Echocardiographic recordings showed a

reduction in heart rate and left ventricular end diastolic volume.

The sympathetic inhibition is due to stimulation of high pressure

baroreceptors and low pressure cardiopulmonary receptors. In this

position there is sympathetic stimulation also due to isometric

contraction of upper limb and neck muscles to support the body (Konar

et al 2000). The net effect of the two will determine the autonomic

response. Orthostatic responses were altered such that the cardiac

output improved more than peripheral resistance to maintain the BP.

Shavasana also brings about a faster recovery after treadmill

exercise compared to sitting in a chair or lying supine (Bera et al

1998).

 

Yoga and the Respiratory System

The various practices use breathing exercises (pranayama),

suryanamaskar, dhyana, devotional sessions, asanas, kriyas, and yogic

chair breathing (Nagarathna and Nagendra 1985; Singh 1987a;

Nagarathna et al 1991). Yogic Kriyas like Kunjal and Vastra dhauti

use warm water and cloth for cleansing of nasopharynx, oropharynx

oesophaus and stomach. The osmolality of fluid may decrease

inflammation and thus reduce the sensitivity of receptors in the

bronchi thereby increasing the threshold of provocation. Sutra Neti

desensitizes nerve endings of the nasal passage making it resistant

to allergens. Kapalabhati removes the residual secretions by moving

the neck in all directions and forcing out secretions forcefully

through the nose. Hence, by this mechanism yoga and naturopathy may

be both useful in treating asthma (Satyaprabha et al 2001).

Pranayama techniques form an important component of yoga. The types

of pranayama generally used are surya bhedana, bhastrika, and nadi

shodana. The idea is to maintain a slow rhythmic pattern of breathing

using both nostrils alternately. This produces a balancing effect on

the ANS. Short kumbhak or breath holding increases O2 consumption

while long kumbhak decreases O2 consumption (Telles and Desiraju

1991). Prolongation of breath holding time with increase in Forced

Vital Capacity (FVC), Forced vital capacity in first second (FEV1),

maximum voluntary ventilation (MVV), peak expiratory flow rate (PEFR)

and lowered respiratory rate has been reported after six weeks of

training in pranayama (Joshi et al 1992). Techniques involving

focusing on a single thought resulted in regularity of respiration

while in the no thought state there was reduction in the rate and

regularity of respiration (Telles and Desiraju 1992a). Savitri type

breathing had a similar effect as deep breathing on cardiovascular

parameters (Madanmohan et al 1986). In a study of patients practicing

hatha yoga, long term manipulation of breathing by practicing slow

deep breathing likely results in overstretching of pulmonary stretch

receptors, chronic manipulation results in vagus blockage, thereby

vagal manipulation is decreased. This also leads to a conditioning or

learning of a pattern of breathing with ample tidal volume and a slow

rate (Stanescu et al 2001).

Various respiratory parameters improve after yoga. A significant

increase in FVC, FEV, FEV1, PEFR, increase in the vital capacity,

tidal volume increase in expiratory and inspiratory pressures, breath

holding time and decease in the respiratory rate is documented to

help symptoms of weekly attacks, and scores for drug treatment.

Improved exercise tolerance, faster recovery after exercise, decrease

in inhaler use, and improvements in bronchial provocation response

has also been documented (Gopal et al 1973; Nagarathna and Nagendra

1985; Yadav and Das 2001; Tandon 1978; Singh et al 1990). This effect

is not merely due to exercise as the sports teachers with training in

physical activity for 8-9 years have also shown improvement (Telles

et al 1993b).

Some asanas used for respiratory disease are Yogic chair breathing,

Vajrasana, Tadasana, Sasankasana, Shavasana, Naukasana, Bhujangasana,

Ustrasana, Urdh hastottanasana, Gomukasana, Ardha Matsyendrasana,

Matsyasana, and Makarasana. In specific yogic postures like

Siddhasana there is a larger tidal volume, O2 consumption, CO2

elimination and minute ventilation compared to shavasana and a

relaxed posture of sitting in a chair (Rai et al 1994). Virasana also

increased minute ventilation, respiratory rate, tidal volume, O2

consumption and CO2 elimination, O2 pulse with a lesser ventillatory

equivalent. The response gets eliminated when the subject retrieves

back to shavasana (Rai and Ram 1993). Shavasana is a calming

procedure while cyclic meditation involves yogic postures along with

periods of supine relaxation. It was found that the results in

decease in oxygen consumption, respiratory rate and increase in tidal

volume compared favorably to Shavasana alone (Telles et al 2000b).

During transcendental meditation there is an increase in respiratory

rate, minute ventilation, oxygen consumption, and co2 elimination,

with no change in the respiratory quotient. There was reduction in

arterial blood pH, lactate levels, and arterial PO2, while PCO2

remained unchanged indicating a wakeful metabolic state (Wallace et

al 1971).

An eight-stepped yoga chair breathing procedure consists of neck

muscle relaxation, and asanas with breathing exercises. This may

reduce the panic anxiety element contributing to aggravation of

bronchial obstruction. The effect seems to be acute, but patients

have been followed for 54 months with beneficial effects. Similar

results to yoga asanas and breathing exercises may be observed by

techniques like progressive muscle relaxation, postural drainage, and

pink city exerciser (Nagendra and Nagarathna 1986; Singh 1987b;

Freedberg et al 1987; Lorin et l 1971). Resistive breathing training

requires the person to breathe against a resistive load. These

respiratory maneuvers may lead to better tolerance of hyperemia,

improve the strength and endurance of respiratory muscles and

decrease the onset of fatigue. Exercise using a bicycle ergometer and

breathing exercises may cause subjective improvement, increase

exercise tolerance without lung volume and ventilation in severe

obstructive disease by improving neuromuscular coordination (Brundin

1974). Yogic exercises and asanas may benefit individuals by similar

mechanisms.

The various mechanisms responsible for the improvement include

reduction of psychological over activity, emotional instability,

vagal efferent discharge and evacuation of sputum. Slow breathing

with and without humidified air had a bronchoprotective and

bronchorelaxing effect, increased autonomic control, and a positive

endogenous corticosteroid release (Nagarathna and Nagendra 1985;

Singh 1987a; Tandon 1978; Singh 1987 b; Jain et al 1991). Yogic

breathing is also known to decrease the chemoreflex sensitivity to

hypoxia and hypercapnia (Spicuzza et al 2000). Pranayama is believed

to decrease the anxiety element as well. Since asthma is a

psychosomatic and chronic disease, a psychosomatic imbalance with an

increased vagal tone is one of its various etiopathogenesis. Yoga

therapy may first bring internal awareness, correct autonomic

imbalance, control the breathing, improve the immune status and alter

physiological variables. Even one week after yoga therapy,

improvements in ventillatory functions in asthmatics have been

observed. This could be due to reductions in sympathetic reactivity

and relaxation of voluntary inspiratory and expiratory muscles. Both

transcendental meditation and yoga have proven to be effective

alternative medicines for controlling symptoms of asthma (Lane 1991;

Wilson 1975). Yoga is also valuable in the treatment of COPD (Behera

1998).

 

Conclusion

The practice of yoga is a tremendous gift from our Indian culture.

Only recently have we begun to understand the vast potentials and

health benefits. However, it has also become fashionable to talk

about yoga rather indiscriminately and yoga is assuming a significant

commercial potential. It can be argued that the benefits of yoga may

be due to the dynamics of group activity and the mere fact that the

person is engaged in any exercise. This psychological aspect can

influence the physiological state. In this context, it is important

to find scientific explanations for the perceived benefits of yoga.

This can also help us to select specific items and individualize

therapies. However, much more needs to be done and it is only a

matter of time when scientific objectivity will be well established.

Presently, it is well known that yoga has become internationally

accepted.

 

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------------------

 

 

Dr. Aaarti Sood Mahajan is Associate Professor of Physiology at

Maulana Azad Medical College in New Delhi, India. She can be reached

at rajeevm

 

Dr. R. Babbar is Professor and Head of the Department of Physiology

at Maulana Azad Medical College.

 

Please address correspondence to:

Department of Physiology, Maulana Azad Medical College, Bahadur Shah

Zafar Marg,

New Delhi. 110002, India