The Valsalva maneuver is not holding ones breath but forcing air through through a closed airway. I can hold my breath with out forcing. Valsalva maneuver - Wikipedia, the free encyclopedia
I use the Valsalva Maneuver to help correct my SVT events.
Not the same dynamics as holding ones breath. A horse will not hold his nostrils and blow out forcefully. Tightening the muscles while performing a forcefull movement (quick stop and turn and etc) can create a grunt or a valsalvic type reaction but its reactionary (involuntary) and mommentary and caused by sudden tightening of muscles that cause one to blow against a closing or restricted ariway. Its not the same as voluntarily holding a breath to create a reaction of lung/chest expansion to keep a girth or strap from being tightened. It is not the same as holding a breath before going under water. It is not the same as being self actualized to voluntarily hold a breath to get a reward. You cannot teach a horse to do this no more than I can teach it not to poop.