Adho Mukh Svanasana or the downward dog pose circulates the blood towards the head and as a result boosts the oxygen in the scalp region and promotes hair growth.
Balasana or the child pose indirectly helps in increasing hair growth as it fights the two main issues for hair fall - stress & poor digestive system.
Vajrasana or the thunderbolt pose helps in improving digestive system of the body and prevents the hair from thinning because poor digestive issues causes hair loss so this asana helps in function in the body better.
Matsyasana or the fish pose stimulates the hair growth and making the hair long, strong and shinier. The blood flows towards scalp and making it perform better.