LOCOMOTION AFTER STROKE

David A. Brown, PT, PhD

Assistant Professor

PhD, University of Iowa

MS, Duke University

BSPT, University of Rochester

Contact Information

Phone#: (312) 908-0976

Fax#: (312) 908-0741

Email: d-brown1@northwestern.edu

Dr. Brown joined the faculty of the Department of Physical Therapy & Human Movement Sciences in June of 1998. Since then he has received an appointment with the Department of Physical Medicine & Rehabilitation, and in February 2000, an appointment with Northwestern University Institute for Neuroscience. 

The focus of his work is directed towards the understanding of neuromusculoskeletal control during active movement in persons with brain injury.  In particular, his studies seek to understand the control mechanisms underlying locomotor behavior in persons with post-stroke hemiplegia.  Related to this objective, his work is attempting to understand underlying mechanisms of poor control and to develop quantitative evaluation and intervention tools for the amelioration of locomotor deficits post-stroke.  The experimental approach includes measurement of electrical muscle activity, lower limb force and movement trajectories, and electro-physiological reflex testing during cyclical locomotor movements such as walking, rising from a chair, and pedaling.

   Current projects with post-stroke populations involve examination of spinal reflex modulation during locomotion, the study of motor adaptation to specific biomechanical constraints, and the development of a new framework for identifying specific locomotor impairments that result in walking dysfunction.  Past and current funding sources include NIH, NIDRR, VA, and Foundation for Physical Therapy.

   Dr. Brown's research investigates the mechanisms that underly walking difficulties in persons with post-stroke hemiplegia. 

   He has developed a laboratory apparatus, based on a bicycle ergometer, that allows the systematic study of functional impairments post-stroke.

Figure.  Schematic of pedaling apparatus used to study mechanisms underlying locomotor deficits in persons with neurological insult.  Apparatus consists of a tiltable backboard that is attached to rollers so that a person, attached by a harness to the backboard, can slide up and down during standing pedaling.  As a result, the pedaler must generate lower limb muscle forces to control the rotation of the crank while simultaneously supporting a specified percentage of their body weight.  With individuals, post-stroke, only low levels of body weight can be supported during this task.  As these individuals recover locomotor ability, they are able to maintain greater amounts of body load while pedaling.

FUNDING

National Institutes of Health; National Institute of Disability Rehabilitation Research; Dept of Veterans Affairs, Division of Rehabilitation & Development; Foundation of Physical Therapy

Selected Publications

Brown, D.A. and Kukulka, C.G.: Human flexor reflex modulation during cycling.  Journal of Neurophysiology,  69:1181-1191, 1993.

Brown, DA, Kautz, SA, and Dairaghi, CA:  Muscle activity patterns are altered during pedaling at different body orientations. Journal of Biomechanics, 29:1349-1356, 1996.

Brown, DA, Kautz, SA, and Dairaghi, CA:  Muscle activity adapts to anti-gravity posture during pedaling in persons with post-stroke hemiplegia. Brain, 120: 825-837, 1997.

Kautz, S.A. and Brown, D.A.:  Relationships between timing of muscle excitation and impaired motor performance during cyclical lower extremity movement in post-stroke hemiplegia. Brain, 121:515-526, 1998.

Brown, D.A. and Kautz, S.A.:  Increased workload enhances force output during pedaling exercise in persons with poststroke hemiplegia. Stroke, 29:598-606, 1998.

Ting, L.H., Raasch, C.C., Brown, D.A., Kautz, S.A. and Zajac, F.E.:  Sensorimotor state of the contralateral leg affects ipsilateral muscle coordination of pedaling. Journal of Neurophysiology,  80:1341-1351, 1998.

Ting, L.H., Kautz, S.A., Brown, D.A. and Zajac, F.E.:  Phase reversal of biomechanical function pairs and muscle activity in backward human locomotion. Journal of Neurophysiology,  81:544-551, 1999.

Brown, D.A. and Kautz, S.A.:  Speed-dependent alterations in force output during pedaling in persons with hemiparesis. Physical Therapy, 79:919-930, 1999.