Exercise Your Breathing Muscles to Run Faster?

According to Matt Fitzgerald, "Your respiratory muscles may also become tired. And to the degree that these muscles fatigue first, it is their fatigue—not that of your legs—that limits your performance. In fact, as your respiratory muscles begin to fatigue, your nervous system will redirect oxygen from the muscles of your limbs to those of your diaphragm to keep them going. Thus, during running your legs may fatigue because your respiratory muscles have begun to fatigue first—and to prevent these muscles from fatiguing to a dangerous extent."   -How Fit Are Your Breathing Muscles

Power-
Lung is probably the industry leader, although I did find a few less expensive options.  I believe there may be something to this- purely subjective but I believe swim intervals helped my breathing- of course those also involve high heart rate, anaerobic metabolism, exhausted muscles, and the rest. 

Can Stronger Breathing Muscles Help Your Running?

An Indiana University study found that strengthening inspiratory muscles by performing daily breathing exercises for six weeks significantly reduced the amount of oxygen these same breathing muscles required during exercise, possibly making more oxygen available for other muscles.-ScienceDaily

Inspiratory Muscle Training (IMT) in this particular study involved forceful inhaling through a hand held device 30 times, twice a day, for 6 weeks. While researchers did not actually demonstrate an improvement in athletic performance, "when the study participants mimicked the breathing required for low, moderate and maximum intensity activities, the inspiratory muscles required around 1 percent less oxygen during the low intensity exercise and required 3 to 4 percent less during the high intensity exercise."

This study Training Breathing Muscles Improves Swimming Muscles' Performance reported "improved respiratory endurance and surface and underwater swimming times by 38 percent and 26 percent, respectively" in subjects who underwent 30 minutes of IMT five times weekly for 4 weeks.

That makes me think I could benefit from this training because try as I might, I seem to use up air faster than most when scuba diving.

So other than maybe sucking hard through a straw a copule times a day, what else can you do to strengthen your breathing muscles? How about playing the harmonica?