Yoga is a psycho–somatic–spiritual discipline for achieving harmony between the mind, body, and spirit, not only with each other but also with the surroundings. Yoga, means “union”, aims to develop the unity, unison, or harmony between the individual consciousness and the universal consciousness. ‘Prana’ refers to “life energy” and ‘pranayama’ means expansion and control of ‘life forces’. It’s been believed that every movement of body and breath alters the movement of thoughts and mind. Pranayama is an art of controlled breathing, which makes the respiration natural (abdominal or diaphragmatic type) and rhythmic (slow and deep) which slowly calms the mind.

Respiration is a unique visceral process. It is mostly under voluntary control, free from autonomic control, but, affects the autonomic nervous system on second to second basis. Fluctuations of autonomic tone during different phases of respiration result in phasic changes of the sinus discharge rate in the heart. During inspiration, para-sympathetic tone falls and the heart rate quickens, and on expiration, the heart rate falls with increased parasympathetic tone. Pranayama practices use the ability of voluntary regulation of breathing to create “voluntary” fluctuations in autonomic tone resulting in re-establishment of parasympathetic dominance, maintenance of autonomic balance leading to de-stress, deep relaxation, increased attention, and memory.

Kapalabhati (KB) involves forceful exhalation and effortless inspiration. During forceful exhalation, increased O2 and reduced CO2 in the blood revitalize and activate the brain cells concerned with memory and other intellectual functions. In addition, air passage opens up, sinuses get ventilated and, thus, chances of respiratory tract infections (sinusitis etc. ) are reduced. It also stimulates the abdominal organs and improves the autonomic balance.

Since ‘Yoga’ is being popularized as a therapeutic tool for various ailments, so it becomes very important to know whether there is any objective evidence of the progress achieved by ‘Yoga’, and if it is there, can it be reflected in terms of reproducible variables.

Yoga practices are found to improve the academic performance of practitioner by reducing the mental stress. Cardiopulmonary responses were found to be rapidly altered and simple problem solving was improved within 20 minutes of the practice of ‘Nadi-shodhana Pranayama’. Cognition is the mental act of acquiring knowledge and understanding via thought, experience, and sensation. Integrated yoga practice was shown to improve the verbal comprehension ability of mentally challenged persons.

A sequential practice of specific ujjayi, bhastrika and Sudarshan Kriya pranayamas alleviates anxiety, depression, stress, and stress-related medical illnesses. It promotes the elimination of CO2 through the lungs which “quiets” the respiratory centers. It probably also invigorates the entire brain and awakens the dormant centers responsible for subtle perception, and thus, signifies the meaning of “Kapalabhati”, i. e. “Shining Skull”. However, Frostell et al. in studying three highly trained yogis performing intense KB, observed that the arterial oxygen and carbon dioxide tension remained normal.

It is also reported that respiration can induce oscillation in various autonomic drives, which lose their concordance under extremes of physiological conditions. Such changes in physiological limits may be forming potent stimuli to induce long-term changes in the autonomic set-up. It is found to reduce the anxiety and increase the sustained attention span leading to improvement in both verbal and spatial memory.

KB shifted the sympathovagal balance by enhancing the sympathetic drive and decreasing the vagal tone. Keeping all the above work in the background, it is hypothesized that 15 minutes of the practice of KB must alter the stress and cognitive parameters in each participant.