[RoyalWulff]

In just about any shooting I do teach to exhale before taking the shot as that way there are fewer muscles involved or tensed, thus making the shooter steadier when the trigger is squeezed. In thinking about how it would relate to golf the only thing I see possible is we all talk about how tension in the arms and uppper body is a swing killer. The exhale might just relax the body enough to help with less tension in the upper body thereby making it easier to swing.
Although this might be streatching things a bit.