Findings of several studies showing beneficial effects of meditation in the reduction of mental stress and anxiety, improvement in pulmonary functions among patients of chronic obstructive pulmonary disease, and improved exercise tolerance among patients of coronary heart disease have been questioned on the grounds that there was often selection of favourably predisposed subjects.
Other weaknesses that have been pointed out are the use of multiple co-interventions, high attrition, and inadequate statistical analysis. It indicates that observed favourable effects of yoga on stress, anxiety, asthma, and coronary heart disease need to be substantiated by more rigorous scientific studies.
However, so far what we have discussed about yoga is not yoga in its true sense. “Yoga” means the union of our individual consciousness with the Universal Divine Consciousness in a superconscious state known as Samadhi. Archaeological evidence and other texts suggest that the methods described in the yoga sutras were being practised as early as 3000 before the common era (BCE).
Oral tradition states that the date may be even earlier. Yoga sutras were historically passed on orally by learned teachers to their pupils. Scholars estimate that Patanjali, who lived sometime between 400 BCE and 200 anno domini (AD), systematized and compiled these sutras.
According to Patanjali, yoga consists of eight steps or limbs, which are all equally important and are related as parts of a whole. The purpose of these eight limbs is discriminative enlightenment or self-realization. But here the emphasis will be on health benefits. The eight steps or limbs of yoga are as follows:
Yama: Codes of restraint, abstinence, self-regulation
Niyama: Observances, practices, self-training
Asana: Meditation posture
Pranayama: Expansion of breath and prana, regulation, control
Pratyahara: Withdrawal of the senses, bringing inward
Samadhi: Deep absorption, meditation in its higher state, the state of perfected concentration