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Ankle load modulates hip kinetics and EMG during human locomotion. J Neurophysiol 2009 Apr;101(4):2062-76

Date

02/06/2009

Pubmed ID

19193774

Pubmed Central ID

PMC2695632

DOI

10.1152/jn.90949.2008

Abstract

The purpose of this research was to examine the role of isolated ankle-foot load in regulating locomotor patterns in humans with and without spinal cord injury (SCI). We used a powered ankle-foot orthosis to unilaterally load the ankle and foot during robotically assisted airstepping. The load perturbation consisted of an applied dorsiflexion torque designed to stimulate physiological load sensors originating from the ankle plantar flexor muscles and pressure receptors on the sole of the foot. We hypothesized that 1) the response to load would be phase specific with enhanced ipsilateral extensor muscle activity and joint torque occurring when unilateral ankle-foot load was provided during the stance phase of walking and 2) that the phasing of subject produced hip moments would be modulated by varying the timing of the applied ankle-foot load within the gait cycle. As expected, both SCI and nondisabled subjects demonstrated a significant increase (P < 0.05) in peak hip extension moments (142 and 43% increase, respectively) when given ankle-foot load during the stance phase compared with no ankle-foot load. In SCI subjects, this enhanced hip extension response was accompanied by significant increases (P < 0.05) in stance phase gluteus maximus activity (27% increase). In addition, when ankle-foot load was applied either 200 ms earlier or later within the gait cycle, SCI subjects demonstrated significant phase shifts ( approximately 100 ms) in hip moment profile (P < 0.05; i.e., the onset of hip extension moments occurred earlier when ankle-foot load was applied earlier). This study provides new insights into how individuals with spinal cord injury use sensory feedback from ankle-foot load afferents to regulate hip joint moments and muscle activity during gait.

Author List

Gordon KE, Wu M, Kahn JH, Dhaher YY, Schmit BD

Author

Brian Schmit PhD Professor in the Biomedical Engineering department at Marquette University




MESH terms used to index this publication - Major topics in bold

Adult
Analysis of Variance
Ankle
Ankle Joint
Biomechanical Phenomena
Case-Control Studies
Electromyography
Female
Functional Laterality
Gait Disorders, Neurologic
Hip
Humans
Locomotion
Male
Movement
Muscle, Skeletal
Orthotic Devices
Posture
Range of Motion, Articular
Spinal Cord Injuries
Torque
Weight-Bearing
Young Adult