I was told as a kid that my horse would hold his breath to expand his ribs and make it difficult to tighten the cinch. That is why it was so important to recheck the cinch before mounting. The adults around me made sure I knew how to raise my knee and make hard contact with the underside of my horse’s chest. It was supposed to force the expulsion of air and make it easier for me to tighten. Although encouraged to repeat this exercise over and over, I do not have any memories of my horse suddenly exhaling a wad of hot air like a gasp gone backwards from previously stubborn lips. Instead, it seemed to just annoy him the more I did it.
Then, I became wiser (not older), and rode many young, old, tall, thin, round and short horses. All of them seemed to do best while tacking up as long as they were relaxed. I learned to walk my horse, check the cinch, walk my horse and check it again before mounting. Technically the ribs are immobile and do not expand. A horse cannot bloat ribs by holding its breath. They can, however, tighten their abdominal muscles and brace the tissue. The chest area becomes hard and unyielding. When the horse relaxes, the tissue softens and thus loosens the cinch. So, all those times I used my knee to bang my horse in the chest, I was actually making the problem worse. the resulting pain was giving my horse a reason to protect himself and brace the muscles.
When cinching up your horse, encourage relaxation. Avoid giving a reason for the horse to brace up in the first place. Put your saddle on your horses back and tighten the girth enough to just hold the saddle on. Walk your horse a few steps and then tighten again. Walking a horse helps to disperse anxiety and bracing. The movement helps them to breathe and relax their abdominal muscles. You can repeat the tighten, walk and check again process as many times as necessary to secure the saddle so that it will not slip sideways or back while riding. I repeat this process 3 to 5 times. You should be able to slip a finger at the cinch between the horse’s legs. That is where the most pressure will be. If you cannot slip one or two fingers between the cinch and the skin, you have tightened too much. This can cause other behavior and performance issues that you want to avoid. And make sure to check you cinch just before mounting. That last check is part of good safety habits and is more for you than the horse.
Whether tightening a western cinch or an English girth, the rules and processes are the same. A good fitting saddle does not need to be excessively tightened. I rode my Arab out on a trail riding event a few years ago for several hours. When I got back to the trailer to unsaddle, I was surprised to see daylight between my horse and my girth. I don’t mean just a little itty bit. The girth was hanging a good inch from his chest. His well fitted saddle and my balanced seat had saved us from slippage. Make sure to check that cinch/girth after riding for a while also.
So, to summarize, check your cinch often and help your horse stay relaxed. Every horse wants the cinch to be like Baby Bear’s porridge – juuuuuust riiiiiight. The largest advantage to keeping your horse relaxed in the tacking up process is that it raises the chances of you having an awesome ride!