Kapala means skull and bhati means ‘shine’. Kapalabhathi thus implies ‘that which makes the skull shine’. The skull or head also stands for intelligence, and hence the term is also referring to ‘that which makes our intellect sharper, brighter’.

Kapalabhati is normally done before other pranayamas. It is very helpful in long meditations, too. During those sessions when one may face dullness, it quickly counters the fuzziness and brings about a certain resplendent quality to consciousness.

In the ancient texts of yoga such as the Gheranda samhita and Hatha yoga pradipika, the kapalabhathi is given as a cleansing, purifying technique.

Additionally, disorders caused by phlegm are supposedly kept at bay, and it also helps to clear the sinuses. Though not stated in the ancient texts as such, the strong exhalations lift the abdominal viscera and diaphragm up towards the lungs, which enhances the expelling action of the exhalations, thus helping to cleanse the lungs.

Alternate nostril breathing refers to a pranayama called nadi-shodhana in Sanskrit. Nadi stands for pathways of subtle energy. In yoga, other than the gross body in which energy and intelligence flow  primarily through nerves, great importance is given to the  subtle energy body or sukshma sharira. This subtle energy body too is suffused with innumerable energy channels through which subtle energy, termed prana, flows. These pathways are called nadis. Though the nadis are innumerable in number (72,000 to 3,50,000), the three most important nadis which yoga practitioners should be aware of are the (1)sushumna, (2)ida and (3)pingala.

Sushumna runs up from the base of the pelvis all the way up into the skull and it ends at the crown of the head. The ida and pingala originate  from a point called kanda, which is somewhere in the region of the root of spine. The ida nadi spirals around the sushumna and ends at the left nostril. It corresponds to moon energy, relating to reflection, withdrawing, calmness, coolness, etc. Its gross body counterpart could be the para sympathetic nervous system.

The pingala nadi spirals around sushumna and ends at the right nostril. It corresponds to sun energy, relating to qualities of action, engaging, effort, radiance etc. Pingala nadi of the subtle body can correspond to the sympathetic nervous system of the gross body.

These energy channels tend to be impure or blocked, which prevents a free flow of prana or vital energy through them, leading to effects in the gross body, such as diseases, fatigue, etc. The nadi shodhana pranayama is the principal pranayama meant to clear this channel of  blocks, which will lend itself to greater health and vitality.

Through its connection to the brain, the alternate nostril breathing also balances the two hemispheres of the brain, apart from the aforementioned effects on balancing any excesses in the drives of sympathetic and para sympathetic nervous system.