The thing about leaning over to reach the bars and easier breathing is that in that position the chest cavity automatically opens up simply due to graityup without as much need of chest muscles contracting for the inhalation part of the breathing cycle. I have book on yoga anatomy which explains in detail how the whole breathing apparatus works. We have all likely seen competitive runners at the end of their event bent over, hands on knees catching their breadth. Furthermore, as a life long asthmatic, I found long ago that the only way to get to sleep during asthma episodes was on hands and knees which expanded the chest. The yoga book made clear why this was so. Being a mechanically minded individiual, I like knowing how things work.
Now, if I could only figure out what that light in my car means that reads "CHECK YOUR ENGINE". The auto dealer doesn't know what it means either.