Dr Bernard Auriol
The Western approach to yoga varies widely:
As for science, it consists mainly in finding the means to observe as much as possible, physiology, cerebral activity, and therapeutics linked to these experiences.
Hatha Yoga and meditation appear complementary rather than alternative therapies for the promotion and maintenance of a good health. They offer an excellent example of the existing connexion between the body and the mind.
With the use of postures or asanas, and in combination with breathing techniques or pranayama, Hatha Yoga brings a balance, on both physical and emotional levels.
Meditation and guided day-dream, not only reinforce physical and emotional activity of postures and breathing exercises, but open the doors to self realization, and enable the thoughts, the body and the mind to be unified. (Gimbel MA, 1998)
Malathi (2000) asked 41 subjects to answer SUBI questionnaire (Subjective Well Being Inventory) before and after a 4 months period during which they practiced yoga. He observed a significant improvement on nine of the eleven scales of the test.
The works of C. Wood (1993 - Department of Experimental psychology, University of Oxford) focused on the effects of three different procedures (stretching through postures, breathing exercises, and visualization during meditation. He assessed the changes obtained on the physical and mental energy perceptions as well as the positive and negative states of humour. The subjects were normal volunteers (N= 71, age range 21-76).
Within the tested protocol, Pranayama appeared to have the highest effects, producing an increase in mental and physical energy, more vigilance and a stronger feeling of enthusiasm. (P<0.05)
Relaxation and visualization made the subjects slightly more sleepy and slow than with pranayama (P<0.05).
The 30 minutes yogic programme including stretching and simple breathing exercises (which can even be done by elderly people), had a noticeable “strengthening” effect on the perception of mental and physical energy as well as the humour of the subjects.
Shell (1994) compared two groups of women (yoga – lecture in a comfortable position), and observed no difference with regards to endocrine parameters and blood pressure. However they observed a reduction of the heart frequency during yoga, more satisfaction, more extraversion, less excitability, agressivity, emotionality, opening and somatic complaints, a better stress and humour management.
Telles (2000) tested a group (n=31) practising yoga over a period of 30 days. (test group). He observed that the yoga group obtained better performances within the labyrinth in comparison to the results of the same test applied 30 days later. This could be due to the composition of the group (faster students), but also to the effects of yoga itself.
Telles (1993) observed the improvement of average static tremometric performance of yoga students.
She applied similar tests to a
group of adults before / after 10 days of asanas, pranayama, meditation, devotional
practice and tratakas (N=20;20). Tremometric task: inserting a stilet through
è contact = error; significant reduction of errors in the yoga group and nothing to report on Telles tests (1994)
Manjunath (1999) observed dexterity after yoga practice: with the standard manipulation of small objects with “tweezers”. The scores obtained by the “yoga” test group were significantly higher where as the standard test group remained stable.
The finger “tapping” task was used in order to assess the motric speed of both hands on 53 adults and 152 children (before and after yoga training), in comparison to 38 adults who did not practice yoga and served as reference. All test participants were right handed. Tapping was assessed after 10, 20 and 30 seconds. The results were improved after 10 days of yoga practice for children and 30 days for adults. However improvement concerned the first 10 seconds and not the following. This means that yoga improved speed but not endurance. (Dash M, Telles S. 1999)
Spontaneous tapping is meant to measure neurophysiological rhythm. This spontaneous rhythm reduces with age without become less stable (cf. Vanneste and coll., 2001)
Critical flicker fusion frequency or CFF) was measured by Vani (1997) on two matching groups (age, sex category, N=18: 18)
The yoga group practised asanas, kriyas, meditation, and attended devotional sessions and conferences. After 10 days no difference was observed on the CFF. However, after 20 to 30 days CFF increased (10 to 15%) in the yoga group and remained unchanged on the other standard test group.
A research conducted by Madanmohan and coll. (1992) shows that yoga practice during 3 months improves significantly auditory and visual reaction time.
Telles(1993) has proved that yoga practice (more than 3 months) on experienced physical education teachers (N=40; more than 8 years of training) had favourable effects on weight, blood pressure, and breathing functions. They also observed a reduction of autonomous excitation and psycho-physiological relaxation (reduced heart beat and breathing rhythms).
Kamei and co-workers (2000, Shimane Institute of Health Science, Izumo, Japan) highlighted during the exercises of 7 yoga teachers, an increase of alpha waves and a reduction of seric cortisol. These two phenomenon were highly correlated (r = -.83).
Hans C. Lou and co-workers (1999) at the Royal Hospital of Copenhagen, tried to examine which parts of the nervous system were modified in a reproducible way during Yoga Nidra meditation activities, and whether these modifications differed to those obtained during standard rest.
Evaluation of cerebral blood flow through position emission tomography PET (150-H20) was carried out on nine young adults, highly trained yoga teachers. In the same time, a spectral analysis EEG was carried out on two of them as well as the measurement of the cerebral blood flow (CBF).
In the state of standard rest, a differential activity was observed on the frontal cortex (dorso-lateral and orbital), the anterior cingular gyrus, left temporal gyrus, left inferior parietal lobe, striatum, thalamus, cerebellum, and other structures implied in the executive attentional network.
During meditation, a differential activity was observed on sensorial and associative posterior cortex , known for their participation to imagery activities, with a notable exception in the primary visual area ( streaked area close to the calcarine sulcus, or Brodman area 17 ).
Herzog and his co-workers (1990) have found that during yoga meditation, regional cerebral metabolic rate of glucose or rCMRGlc) is significantly higher on the frontal pole than on the occipital pole of the brain (p<0.05). These indicators show that the cerebral metabolism is more homogeneous during yoga meditation. Vyas and his co-workers (2002) have studies the effects of meditation on the respiratory system, cardiovascular system and the lipidic profile.
In this study, respiratory functions, cardiovascular parameters and lipidic profile of meditation and Raja Yoga practicants (short and long-term meditation practicants) were compared to those of non practicants. Practicants had a significant higher vital capacity, current volume and air retention level.
Long term practicants have higher vital capacity and expiratory pressure than others.
Diastolic blood pressure was markedly lower on meditation practicants. Cardio frequency was markedly lower on long term meditation practicants that on others. Lipidic profile has shown a significant reduction of cholesterol level in the serum of meditation practicant, with similar physical activity. This proves that yoga meditation provides significant improvement of respiratory functions, cardiovascular parameters and the lipidic profile.
Different meditation methods
Bernardi and his coworkers (2001) have shown that rosary or mantra recitation with reduced breathing rhythm to six inhalation per minute, inducts favourable psychological effects as well as physiological effects (increase of pre-existing cardiovascular rhythms, increase of “baro-reflex sensitivity “ which regulates blood pressure).
Telles (2000) has compared cyclic combination of stimulating and calming exercises (cycles) after shavasana. On both methods, she observed a significant reduction of respiratory rhythm, an increase of the respiratory volumes and a reduction of oxygen consumption. However the difference was significantly higher on cyclic meditation.
Corby (1978) has shown that experienced tantric meditation practicants have a increase in alpha and theta on the EEG, no sign of sleep, little reaction to the autonomous system to the external stimuli. However approaching ecstasy was manifesting through a sudden activation of the sympathetic system.
Kundalini yoga / relaxation
Narayan (1990) has tried to assess (EMG) the degree of muscular relaxation obtained during kundalini yoga. He observed (N=8, 4 men, 4 women) a 58% reduction in comparison to the reference (base line) on men and women.
Telles (1993) studied 25 adult men with 5 to 25 years of brahmakumaris meditation practice (Raja Yoga). This technique requires high implication and concentration. Observations showed that cardiac frequency increases during this form of meditation.
However there was no crucial change during meditation, on the entire group, with regards to Galvanic skin response (GSR), finger plethysmogramme PPG amplitude and respiratory rhythm.
RESEARCH ON RESPIRATORY PHENOMENON AND PRANAYAMA
Improvement of respiratory physiology
Makwana’s work and coworkers (1988) carried out research activities on 25 men’s respiratory functions after 10 weeks of yoga practice. Ventilatory functions were improved: reduced respiratory rhythm, increased vital capacity, maximum respiratory capacity and breath retention, though current volume and Tiffeneau’s report did not show any evident changes.
Research carried out by Madanmohan and co-workers (1992) showed that a three months yoga practice increases significantly classic ventilatory indexes, breath retention with empty and full lungs, and the Hand Grip Strength.
Birkel (2000) confirmed (287 cases) that yoga increases vital capacity.
Telles and co-workers (India) devised 28 anxious girls into two groups, and had them into pairs of same age and same length of attendance in the centre. Within each pair, one was assigned for yoga (relaxation) and the other for active game for a period of 6 months.
Both groups presented a lower cardiac frequency at the end of the period (Wilcoxon Test), additionally the yoga group had also a reduced breathing rhythm, which indicated a stable reduction in the level of stress and anxiety.
Yoga and breathing at altitude
Bernardi and co-workers (2001) studied the effects of altitude simulation on yogis in comparison to a test group.
The breathing rhythm per minute increased on the test case, but remained unchanged for the yogi.
In all cases oxygen saturation decreases, however it decreases less for the yogis than the other standard cases, whether it is during spontaneous breathing, controlled breathing or slow yogic breathing.
Altitude generates sympathicotonia (cardiac acceleration, variable pulse and systolic pressure on the test group, whereas yogis are far less affected by the effects of altitude. The effect can be reduced by voluntary slowing-down of the breathing on both cases (yogis and test group).
This indicates that slow yogic breathing is more efficient, since it maintains a better blood oxygenation without any increase of ventilation per minute. It reduces sympathicotonia, resulting from hypoxia, altitude simulation.
Lateral Breathing (nostril breathing)
The “Svara” concept considers correlation between lateral dominance of the nostril breathing (nostril dominance), and stages of rest (ida), activity (pingala) and turbulence (sushumna). Mohan (1996) has measured nostril dominance and galvanic skin resistance (GSR) as an indicator of the ortho-sympathetic stimulation.
The ortho-sympathetic activity was low in Ida Svara, strong on Pingala Svara, and at its peak on Sushumna Svara (assessed according to traditional criterias).
Conference in Lisbon – Portugal, (European Convention Yoga, Yoga therapy and Ayurveda), 21 October 2006
And in Foix, France (Grep-Mp, March 2005)
5 April 2007