Try this for me, take a deep breath in, what happened? Did your belly button move in or move out? If it moved in then you are a golfer that has an inverted breathing pattern, this prevents the spine from being pumped nauturally with cerebral spinal fluid, lubricating each individual spinal segment.
Try this at home lie in a supine position, on your back in what I call the animalistic position, when on the horizontal plane the brain shuts down and is much quieter, hence why sleep is activated in this position, with a bottle of water filled one third of the way, resting it on the belly button area, breath in through the nose allowing the bottle to raise towards the sky and out through the nose allowing the bottle to lower, the supine position allows gravity to work against the bottle thus making this a weight bearing exercise.
This exercises allows for a deeper more diaphragmatic breath, mobilising the rib cage, lengthening the spine and aiding a more aligned posture which is only a good thing for the golf swing.
Happy Practicing.