A new study is available from America discussing the effects of Power lung.

This clinical evidence evaluates if the practice of exercising respiratory and extra-respiratory muscle would make a signifant change in both VO2max and performance in collegiate cross-country runners. From previous studies on pulmonary function, it is known that the diaphragm fatigues after 10 minutes of exercise.
Even though support from the extra-diaphgrmatic muscles are able to compensate, they will also fatigue after time and eventually decrease performance. PowerLung increased respiratory strength, but did not lead to an increase in VO2max, latate threshold or total perofrmance during maxmimal treadmill test.

However, it is suggested that pulmonary compromised individuals have a greater room for improvement and would most likely benefit from utilizing PulmoLife compared to seasoned collegiate athletes. You can read more about the clinical evidence here, The Effects on Pulmonary Function and Performance from Training Respiratory Muscles in Collegiate Cross Country Runners with PowerLung.

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