As per Yoga, Sveda is a natural phenomenon associated with the human body through which the body sheds extra water, along with some inorganic salts and organic products, to maintain its normal temperature. Sveda is a watery secretion of the sweat glands which produces a cooling effect on the surface of the body.
In Yoga, the phenomenon of production of sveda is associated with the practice of pranayama. According to intensity of practice, pranayama is classified into three categories, such as
- Kanistha (the lowest or moderate)
- Madhyama (the middle type)
- Uttama (the highest or best)
This is based on the duration of each holding of breath (kumbhaka) and the number of kumkhakas in a sitting. Pranayama of the highest intensity, as mentioned in Hatha Yoga Pradipika (II.11), consists of four sittings every day, of eighty kumbhaka each, with each kumbhaka taking forty-eight second. The lowest type has one-fourth measure of the best one, and the middle has half the measure.
The lowest type is said (II.12) to give rise to sweating (sveda), the middle one to vibrations (kampana), and the highest one to self-realization (paramapada). It is said further (II.13) that when there is sweating, the student should do massage of the body with the watery fluid. This is said to make the body parts firm (drdha) and light (laghu). The fact of production of sveda by doing the lowest type of pranayama is also mentioned in Trisikhi Brahmana Upanishad (104).