1. Breathing Research and Therapeutics Center, Department of Physical Therapy, University of Florida , Gainesville, 32603 , USA
2. Department of Physical Therapy, Thomas Jefferson University , Philadelphia, PA, 19107 , USA
3. School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham , Edgbaston, Birmingham, 3- B15 2TT , UK
4. Department of Biostatistics, University of Florida , Gainesville, 32603 , USA
5. Brooks Rehabilitation , Jacksonville, FL, 32216 , USA