From the first texts, hatha yoga goal has been the extension of life and getting rid of diseases.
Including energy practices were aimed at improving health. Thus, Amaraugha-Prabodha writes:
“Hatha yoga is what is used to structure pranas (energies) ...
The body is made up of five elements and five chakras.
When the [element] of earth decreases, wrinkles appear in people. When the water decreases, the hair gradually turns gray, like dried grass. When the fire decreases, appetite disappears, when the wind dissipates, beauty disappears, trembling occurs, and effort is needed for life.
Many hatha yoga texts point to health benefits as an effect of asana practice −
“śarīrāntargatāḥ sarve rogā vinaśyanti । viṣāṇi jīryante ।
Then [after asana], diseases that have entered the body disappear, poisons grow old.“
In the 20th century, hatha yoga became close to European medicine through the works of yogis - Desikachara (Viniyoga of Yoga), Shri Yogendra (Personal Hygiene of Yogi) and Dhirenda Brahmachari (Yoga Sukshma Vyayama). In their books, they noticed the correspondence of exercises for the body and breathing to the treatment of various diseases.
For its part, medicine also stepped towards yoga, this step is yoga therapy — the treatment of diseases and their prevention by means of yoga.
Yoga therapists in their experiments measure how asanas and pranayamas change the state of health of a yoga practitioner.
From these studies, advice is born on applying asanas and pranayamas to the treatment of various diseases. And also about the nuances of practice in case of health defects.
Thus, we practice hatha yoga exercises based on both classical texts and modern knowledge.