It is well known in modern physiology that in our human system large number of cells get formed continuously and equal number of cells get destroyed. Medical researchers have found that in about seven years almost all the cells in our body get replaced.
Prana refers to the life-force or the vital energy, which is responsible for all the functions, physical and mental, in the human being. Ayama refers to the ability to control your body by stretching, expanding, and elaborating. Hence, pranayama refers to the control of prana by stretching it. Breathing is the means through which control of prana is brought about. While in Patanjali’s Yoga Sutras, breathing is emphasized in pranayama practices; in Hatha Yoga, retention or kumbhak is emphasized. In fact, Swatmarama in Hatha Pradipika refers to eight varieties of kumbhak, instead of pranayama. These eight varieties are as follows: