First off: I am no fan of these bits - at least not in inexperienced hands. (No knowing how experienced you are! Just my two cents here.)
Secondly, it's not so much in the equipment as in the hands that uses them.
.
Originally, this bit was used for driving, until Nelson Pessoa (famous rider) started using them. Their "real name" is "Dutch gag", which says more about it IMHO.
.
It is not a "leverage bit", like the Pelham, since it has no chain. Consequently, there is nothing to stop the rider from pulling back "too much" at the reins. If you do put a chain on it, it won't be sitting in the right position, and cause pinching instead.
When you take the reins on a Pessoa, the bit will press up against the corners of the mouth as well as the palate - causing the horse to raise its head - while the shanks will rotate and create a pressure on the horse's poll = conflicting messages, and probably painful too.
.
The horse will most likely bend his neck to escape both pressures (pain) and will "end up with a prettily curved neck (behind the bit) but his hind feet left in the barn". (As an old instructor once described it to me ;) ) Which is why I am a bit boggled as to why your masseur would want you to use it to get the hind leg more active.
The only use I can think off is on a very obedient, but "hot", horse that already works well from behind, but where the rider wants to be able to be very light in hand, yet extremely precise, to cause less distractions/confusion.
.
Furthermore, giving the rein is not really possible since the bit is over-mobile and therefor you have to release them completely to get the desired contact with the mouth.
At least in English riding, that is useless since you want to be able to ask with the reins - give and take - to maintain an honest contact where the horse moves forward from behind "into your hand".
.
The Pessoa is often used on horses that gets strong and want to rush off, since it gives the rider a (false) sense of lightness in hand and less energy to rein back the horse.
Since the bit lacks any form of lever, you feel as if you have a lot less in your hand, while in truth the horse has gone off the bit because the effect is too sharp.
If you then pull back more on the rein to "feel" some contact, the effect will be at least the double in the horse's mouth/poll, and he will just drop off the bit even more.
.
I do agree on the idea that your horse needs to get that right hind leg working, but I don't see how a gag will have that effect.
Regardless of style (English/Western) I'd say you need to ride him forward for both legs/seat, and do lots of half halts and transitions to get him to work from behind and create that "sit-ups" effect that will muscle him and help him balance himself. Pole work - in hand or ridden - on circles or other patterns is helpful too.
.
Sorry this was so long!
Good luck!

Around my barn, for lunging, people use a pessoa. This equipment has a surcingle with a rope thing that goes behind the hind legs and comes with side reins. I am assuming that this would achieve the same goals that Monty would get with his double line lunging. I too would like to know if this assumption is correct and is favourable lunging equipment, assumming again if this is what mickydavies86 wasasking about.

Beautifully stated Kicki. The art is NOT to torture the animal but to learn how to let the horse be a horse but willingly wanting to be in partnership with the rider. It amazes me whow we humans think if we dont see it, the problem is gone. Gaging a horse into obedience is just wrong. To get the hind legs involved requires first ruling out there is/are not any physical reasons (let the Chiropractor check it out), then making sure you are not giving mix signals and finally coming up with SAFE, exercises and manuvers that strengthen the muscles needed to get the correct move. If you want to teach a child to avoid touching a hot stove, you would not stab them in the leg would you? I hope to hear a LOUD no!! Keep that in mind when wishing your horse comply with your REASONABLE wishes!!

Hmmm...
EvyG, you make me think I have misunderstood the original question.
There is indeed a type of lunging device with ropes behind the horse's shins that Pessoa has developed. It makes a lot more sense to me if that's what the masseur suggested.
It is intended to get horses' hind legs more active and underneath them, plus making them stretch their necks/back, BUT, as the line around the hind legs attach to the bit, the horse will get yanked in his mouth at every step.
.
May I suggest that you take a look at this informative site: http://www.sustainabledressage.net/tack/gadgets.php
Especially this part:
http://www.sustainabledressage.net/tack/gadgets.php#pessoa
.
May I suggest that if you need a gadget to help your horse, that you follow the suggestion on that very site about using a chambon and a simple rubber neck extender behind the horse and attached to the surcingle. :)
http://www.sustainabledressage.net/tack/gadgets.php#2part_chambon

Thanks kicki. I did not realize that this lunging device with the ropes attaches to the bit. I will have to ask to see it more closely when one of my barn "buddie" uses it to lunge. I have never lunged my horse as I ride him most every day. I will take a look at the site - because everyone raves about this device at my barn - I just assumed it was because it achieved the same results are double line lunging.

Thankyou for all your comments advice,I have had my mare checked for all back,teeth muscle,tack ect problems.I dont ride her in a bit only a dually or dr cooks bitless, as when she first came she freeked at the bit. Although now she will accept it, i prefer not to use it,as she is very sensative.
So if i do use the pessoa it would be on a dually on long reins.We think she has an old injury on her right hind which i would like to make stronger

MICKY

I know nothing about this bit but from reading the comments it sounds horrible,especially since you ride with a dually or a bitless.If I was you I would forget the gadgets and do
the excercises because building muscle and strengh takes some time.You want to help the problem not just have it look corrected.

I seriously doubt that you are being told to use a pessoa bit. the device your masseur was telling you to use is a pessoa training system. It works on bungee ropes and has a section running above the hocks.
The pessoa can be a usefull training aid in the right circumstances, teaching the horse to engage his hind quarters, however it will encourage the horse to lean on the bit or even worse carry himself behind the bit. I have used all sorts of training devices and honestly! a dually halter and a set of long lines is the best way to go. These used correctly can encourange your horse to carry himself, stretch through his back and move forward. I hope this helps.x

Oh dear, such conflicting advice! The Pessoa training aid which I believe is what was suggested, does indeed encourage the horse to lower his head and engage his hind quarters. If the instructions that come with it are followed it does not encourage the horse to lean on the bit,quite the reverse in fact. The padded area of the pessoa that passes around the horses hindquarters is indeed a bungy and it is the line connected to this that passes through a pulley-wheel attached to the bit or Dually before attaching to one of three positions on the roller. The first of these positions being between the horses forelegs.
The horse is able to raise or lower his head as he pleases and will find the most comfotable position to work in, it is suggested that in the first instance the lines are fitted with minimal contact. As the animal gets fitter it is easy to see if and when the lines need adjusting or moving to a higher position.
If the horse is to be longed it allows/encourages him to keep his spine bent on the circle (as does long lining) but is a lot easier to manage for anyone who is less adept with long lines (and more beneficial to the horse if a bit is being used).
Smaller children and less skillful riders are often unable to "ride the horse on" so that the hindquarters are engaged, appropriate use of a pessoa encourages the horse to adopt this way of going, as he will find for himself that it is the most comfortable,effecient and natural way to proceed.
Some years ago whilst attending one of Monty's demos in Scotland, I watched him looking at a horse being worked in a Pessoa. Later during his demo he praised the device and its method of working.
Not infrequently I work with Highland ponies, some of them are not at all forward going and are very heavy on the forehand, in such cases i do not hesitate to 'loose school' them in my roundpen using a pessoa. I hasten to add some highland ponies can be very light and athletic!
Right that's my rant over, I hope I haven't offended anyone and may possibly even have helped.

Thanks Val. Your comments are very informative.

Thanks from me too, Val!
Very interesting and informative to be able to read a POV from someone who is using a device correctly.
It's always in the hands of the user - seldom in the device itself!

Val,
Bravo for your post, I found it factual & informative. I too was begining to read the previous posts thinking "folks are getting their wires crossed here!" I have experienced vets/back specialist`s recommending the Pessoa Training System. I strongly agree with Kicki - It`s always the hands that hold the reins, bit or device. Lightness is key!
I also agree that it is important to read & follow the instructions given with it. In the wrong hands or used incorrectly, as with any "artificial training aid" you can do more damage than good.