[1] Northwestern Univ, Dept Phys Therapy & Human Movement Sci, Chicago, IL 60611 USA
[2] Univ Illinois, Dept Phys Therapy, Chicago, IL USA
[3] Rush Univ, Med Ctr, Dept Neurol Sci, Chicago, IL 60612 USA
[4] Rush Univ, Med Ctr, Dept Prevent Med, Chicago, IL 60612 USA
[5] Univ Colorado, Sch Med, Div Geriatr Med, Aurora, CO USA
[6] Rush Univ, Med Ctr, Sect Parkinson Dis & Movement Disorders, Dept Neurol Sci, Chicago, IL 60612 USA
[7] Univ Florida, Dept Appl Physiol & Kinesiol, Gainesville, FL USA
[8] Univ Florida, Dept Biomed Engn, Gainesville, FL USA
[9] Univ Florida, Dept Neurol, Gainesville, FL USA