There are anecdotal examples of activities that breathing interventions can support sports performance and have functional implications. Some competitors sleep with a weight on their chest to strengthen breathing muscles and increase their capacity to force air in to the lungs. For breathing enhancement, some individuals use straw breathing to restrict airflow to stimulate the impulse to inhale. Research has been done on pulmonary function and physical performance, where it may be presumed that participants have highly functional responses.

 

Physical performance is limited primarily by the muscular, cardiovascular, and respiratory systems. In healthy individuals, the systems limiting performance follow a hierarchical order from sedentary subjects being restricted by muscle function; then, generally fit individuals having cardiovascular constraints on physical efforts, with elite athletes many times reaching the ceiling effect because of pulmonary restrictions. Environmental factors may also contribute to exercise limitations, especially altitude.