Ashwini Mudra — also called the Horse Gesture Pose — is a Tantric Hatha Yoga technique that consists of repeatedly and briefly contracting the sphincter muscles of your anus, and then relaxing them. It can be performed in sitting, lying, inverted, or standing position, and in conjunction with a Bandha, and typically, each contraction and relaxation is done for a few seconds.
The exercise relaxes the entire region of the pelvis along with the perineum, pelvic floor, buttock and sphincter muscles. The actual Yogic goal is to move Prana Life Force upwards, through the Sushumna Nadi Energy Channel, for spiritual benefits. This includes being an exercise to activate the Muladhara Chakra and awaken Kundalini Energy aka Shakti Energy.
Other benefits are the improvement of blood circulation in the pelvic region, strengthening of the rectal, lower abdominal and pelvic floor muscles, and relief of digestion issues, constipation, excessive gas, and hemorrhoids.
Ashwini Mudra is also used to increase sexual health, improve sperm count, help against Premature Ejaculation (PE), to make sex more pleasurable, and for sexual energy retention and cultivation. It can be applied for Semen Retention purposes — in the moment or as a structural exercise — but it also brings more force, virility and sexual stamina.
Some precautions and contraindications with regard to Ashwini Mudra need to be taken into account though: those who are pregnant, have an anal fistula, uterine issues, slipped spinal discs, pelvic or abdominal organ prolapse, high blood pressure, or recent abdominal surgery should avoid practicing this exercise, or at least first seek professional healthcare advice.