Prevent Fatigue by Training Your Respiratory Muscles

In the final miles of a long run or triathlon run, your leg muscles become very tired. 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 triathlete is aware he or she breathes hard when running (or swimming or cycling) 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 suggests respiratory-muscle fatigue is a limiting factor in endurance sports performance. What's interesting is 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 triathlon performance.

Some studies of respiratory-muscle training have shown no performance benefit, but others have shown benefits in all three triathlon disciplines. I'm inclined to believe it may be most beneficial for running performance, as the body demands more oxygen during running than it does during swimming and cycling. Also, since the run is the last event in a triathlon, the respiratory muscles are most likely to become fatigued therein.

Testing a Theory

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 VO2 max 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 important, 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 marketed primarily to athletes.

Testing a Device

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.

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