How Fit Are Your Breathing Muscles?

Respiratory muscle training may help you run better.

Written by: Matt Fitzgerald

In the final miles of a long or hard run, your muscles become very tired.  Which muscles?  Why, your leg muscles, of course.  But your hamstrings, quadriceps and calves are not the only muscles that become fatigued during a hard run, nor are they necessarily the first muscles to bonk.  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.

Every runner is aware that he or she breathes hard when running hard.  But few pause to consider that hard breathing requires intense work by the respiratory muscles, which are just as susceptible to fatigue as other muscles.  There is scientific evidence that respiratory muscle fatigue is a limiting factor in endurance sports performance.  What’s interesting is that these muscles may be trained independently of the rest of the body.  You’re almost doing it right now, as you sit still and breathe.  Naturally, everyday breathing is too easy to have a conditioning effect on your respiratory muscles, but when you inhale and/or exhale against resistance with a respiratory muscle training device, these muscles may be taxed even more than they are when you swim, bike and run.  As a result, they become stronger and more fatigue-resistant and therefore less limiting in your running performance.

Some studies of respiratory muscle training have shown no performance benefit, but others have shown benefits in running, as well as in swimming and cycling.  Among the better studies showing a performance benefit resulting from respiratory muscle training was one conducted by exercise scientists from the University of Arizona.  Twenty cyclists with an average VO2max of 56.0 ml/kg/min participated in the experiment.  Half of them, representing an experimental group, performed 20, 45-minute respiratory muscle training sessions in addition to their regular bike training.  Four others, representing a placebo group, performed 20, five-minute “sham” respiratory muscle training sessions in addition to their regular bike training.  The remaining six riders, representing a control group, just did their regular bike training.

After completing the 20 sessions, members of the experimental group exhibited a 12-percent increase in their respiratory muscle endurance capacity. More importantly, their performance in a bicycle time trial designed to last approximately 40 minutes improved by 4.7 percent, with nine of the 10 subjects in this group showing some improvement. There were no improvements in either respiratory muscle endurance or time trial performance in the placebo group or the control group.

Experiments such as this one usually involve fancy and expensive respiratory muscle training devices normally used to treat chronic obstructive pulmonary disease.  But there are some relatively inexpensive devices that are marketed primarily to athletes.  The oldest and best known is PowerLung, which has been around since 1999 and currently sponsors the Slipstream professional cycling team.  The folks at PowerLung were kind enough to send me their Trainer device recently (MSRP: $109) so I could try respiratory muscle training for myself.

The PowerLung Trainer looks like an overbuilt plastic kazoo with a snorkel’s mouthpiece at the business end.  It is almost as easy to use as a kazoo.  One of two numbered adjustable twist knobs varies the amount of resistance the device imposes against inspiration (breathing in).  The other knob varies the amount of resistance your expiratory (exhaling) efforts meet.  In my first PowerLung session I just played around with these knobs and practiced breathing through the device until I felt I had found an appropriate starting level.  Thereafter, in obedience to the literature that came with the PowerLung, I did two brief respiratory muscle training sessions per day: the first during my morning commute and the second during my afternoon commute.  (Yes, I got more than a few strange looks from other drivers.)

Within a matter of days I began to notice a training effect.  It became easier and easier to complete the same number of repetitions with the same amount of resistance, so I incrementally increased first the number of repetitions and then the resistance.  It’s now been about eight weeks since I started using the PowerLung, and while the strength and endurance of my respiratory muscles are markedly improved, I still can’t say that I’ve noticed an obvious improvement in my running performance resulting directly from these changes.  There have been moments, however, in hard workouts when I have felt less limited by my capacity to draw air—when my lungs have seemed to be coasting along even as my legs have begged for mercy.  But it could be a placebo effect, for all I know.

When you’ve been an endurance athlete as long as I have, you have to start looking in out-of-the-way places for improvement.  And it can be difficult to judge whether or to what degree a particular new out-of-the-way measure has contributed to any improvement you do experience.  Sometimes you have to take a leap of faith based on the results of controlled scientific studies showing that a particular tool or method really works.  Such is the case with respiratory muscle training.  Several good studies have shown it enhances endurance performance when done properly.  So if you’ve been a runner for some time and are already training as hard as you’re ever going to train, you might want to try respiratory muscle training.

[sig:MattFitzgerald]