1 The Department of Physical Medicine and Rehabilitation, UAB Heersink School of Medicine, The University of Alabama at Birmingham, 1717 6th Avenue South, Room R156, Birmingham, AL 35249, USA. Electronic address: xzhou@uabmc.edu.
2 The Department of Physical Medicine and Rehabilitation, UAB Heersink School of Medicine, The University of Alabama at Birmingham, 1717 6th Avenue South, Room R156, Birmingham, AL 35249, USA. Electronic address: cmrenfro@uabmc.edu.