Running Martingale: The English running martingale is similar in form and function to the training fork popular with western riding. The running martingale attaches to the girth and then runs up between the horse’s front legs, where it splits into two narrow straps, each ending in a large metal ring. A neck strap holds the forked leather in place so the horse can’t become tangled in the apparatus. The reins run through the rings. When adjusted properly, the running martingale exerts downward pressure on the reins only when the horse raises its head above the pre-set level. Then, in response, the horse lowers its head back to the desired position, and the pressure is released.
Make sure the horse understands the basics of flexing at the poll and yielding to bit and rein pressure before introducing a running martingale.
Leather or rubber rein stops are vital. They are slid onto the reins and prevent the martingale rings from snagging on the hardware that buckles the reins to the bit.
A small rubber doughnut is also worked onto the neck strap so the forks of the martingale cannot slide too low between the horse’s front legs.
If the horse tosses its head or otherwise fights against the running martingale’s intended purpose, then it’s probably adjusted too short.