Jalandhara Bandha is also called as Chin-Tuck in English. Mechanical pressure is the main concept of this technique. Mechanical disturbance of carotid sinuses initiates the cardiac center at the brain stem. Initially there will be increased heart rate but later on, it will be reduced because of the Baro-reflex sensitivity. Hence the autonomic nervous system adjustability happens over a period of practice. Being at a small place, Yogi can modulate the blood pressure and heart function as per the environmental requirements. But this has to be learned and practiced under the supervision of an expert. Here is the briefing diagram for beginners.
Advance Yoga Teacher Training must know such sacred practices with dedication and experience under the guidance of experts. Then the Yoga teacher training will not be just a certification course but also the evidence-based practice.