they can be very helpful when used correctly. you mostly see them in the equitation to help make a horse round and keep them in a nice frame. i like them but only if the horse needs it
pelhams are great w the right horse and the right rider. i ride in one w my somewhat stronger horse (@ the shows) & he goes so well! he goes in a snaffle @ home, & we show in the equitation so w two reins on the pelham, it is easier for me to get him round (he's part thoroughbred lol). however, used in the wrong ways, pelhams can be detrimental to a horse's health.
Can be harsh in the wrong hands but heard that when ridden with 2 reins they can be helpful for strong horses because you can use the top rein as a normal rein and then if your horse runs through that rein you can pack it up with the 2nd rein (I haven't used one personally but I have friends who have told me this)☺️