title: Locomotor training improves premotoneuronal control after chronic spinal cord injury.
abstract: Spinal inhibition is significantly reduced after spinal cord injury (SCI) in humans. In this work, we examined if locomotor training can improve spinal inhibition exerted at a presynaptic level. Sixteen people with chronic SCI received an average of 45 training sessions, 5 days/wk, 1 h/day. The soleus H-reflex depression in response to low-frequency stimulation, presynaptic inhibition of soleus Ia afferent terminals following stimulation of the common peroneal nerve, and bilateral EMG recovery patterns were assessed before and after locomotor training. The soleus H reflexes evoked at 1.0, 0.33, 0.20, 0.14, and 0.11 Hz were normalized to the H reflex evoked at 0.09 Hz. Conditioned H reflexes were normalized to the associated unconditioned H reflex evoked with subjects seated, while during stepping both H reflexes were normalized to the maximal M wave evoked after the test H reflex at each bin of the step cycle. Locomotor training potentiated homosynaptic depression in all participants regardless the type of the SCI. Presynaptic facilitation of soleus Ia afferents remained unaltered in motor complete SCI patients. In motor incomplete SCIs, locomotor training either reduced presynaptic facilitation or replaced presynaptic facilitation with presynaptic inhibition at rest. During stepping, presynaptic inhibition was modulated in a phase-dependent manner. Locomotor training changed the amplitude of locomotor EMG excitability, promoted intralimb and interlimb coordination, and altered cocontraction between knee and ankle antagonistic muscles differently in the more impaired leg compared with the less impaired leg. The results provide strong evidence that locomotor training improves premotoneuronal control after SCI in humans at rest and during walking.
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois; Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg Medical School, Chicago, Illinois; Graduate Center/The City University of New York, New York, New York; and Department of Physical Therapy, College of Staten Island, Staten Island, New York Maria.Knikou@csi.cuny.edu m-knikou@northwestern.edu.
authors.forename: Maria
authors.initials: M
authors.lastname: Knikou
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois;
authors.forename: Chaithanya K
authors.initials: CK
authors.lastname: Mummidisetty
mesh_terms: D000328:Adult; D002908:Chronic Disease; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D020233:Gait Disorders, Neurologic / Q000209:etiology / Q000503:physiopathology* / Q000534:rehabilitation*; D006181:H-Reflex; D006801:Humans; D008297:Male; D008875:Middle Aged; D009048:Motor Skills; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology*; D009433:Neural Inhibition; D009469:Neuromuscular Junction; D011597:Psychomotor Performance; D013119:Spinal Cord Injuries / Q000150:complications / Q000503:physiopathology* / Q000534:rehabilitation*; D009435:Synaptic Transmission; D016896:Treatment Outcome; D016138:Walking; D055815:Young Adult
keywords: H reflex; interlimb coordination; neuromodulation; neuroplasticity; spinal reflexes and circuits