Locomotor training improves reciprocal and nonreciprocal inhibitory control of soleus motoneurons in human spinal cord injury

Abstract

In this work, we examined changes of reciprocal Ia and nonreciprocal Ib inhibition after locomotor training in 16 people with chronic SCI. The soleus H-reflex depression following common peroneal nerve (CPN) and medial gastrocnemius (MG) nerve stimulation at short conditioning-test (C-T) intervals was assessed before and after training in the seated position and during stepping. The conditioned H reflexes were normalized to the unconditioned H reflex recorded during seated. During stepping, both H reflexes were normalized to the maximal M wave evoked at each bin of the step cycle. In the seated position, locomotor training replaced reciprocal facilitation with reciprocal inhibition in all subjects, and Ib facilitation was replaced by Ib inhibition in 13 out of 14 subjects. During stepping, reciprocal inhibition was decreased at early stance and increased at midswing in American Spinal Injury Association Impairment Scale C (AIS C) and was decreased at midstance and midswing phases in AIS D after training. Ib inhibition was decreased at early swing and increased at late swing in AIS C and was decreased at early stance phase in AIS D after training. The results of this study support that locomotor training alters postsynaptic actions of Ia and Ib inhibitory interneurons on soleus motoneurons at rest and during stepping and that such changes occur in cases with limited or absent supraspinal inputs.

Rehabilitation Strategies after Spinal Cord Injury: Inquiry into the Mechanisms of Success and Failure

“…Notably, the Ib facilitation of the soleus H-reflex obtained with medial gastrocnemius nerve stimulation in spinal cord-injured individuals returned to the normal Ib inhibition after training when evaluated in the sitting position. During stepping, the Ib inhibition was decreased at early swing and increased at late swing in AIS C, and decreased in early stance in AIS D. 165 This was similar to the reduction in Ib inhibition seen in ablebodied subjects during the stance phase, 166 but the reversal from inhibition to excitation seen in the intact cat 167,168 was absent. It is also interesting that the reflex modulation produced by locomotor training varied based on the amount of spared functions.…”

Supraspinal Control Predicts Locomotor Function and Forecasts Responsiveness to Training after Spinal Cord Injury

“…71 Persons with SCI who participate in locomotor training demonstrate more typical modulation of spinal reflex excitability after training compared with their pre-training levels. [72][73][74][75] The importance of changes in reflexes should be considered in conjunction with observable improvements in overground walking; for example, improvement in overground walking speed is correlated with reduction in clonus and H-reflex magnitude. 73,76 The observation that reflex modulation can change in the absence of measurable change in the walking outcome, 77 however, suggests either that the reflex modulation is an epiphenomenon unrelated to walking performance or that the walking measures are not sufficiently sensitive to the changes in gait that accompany improved reflex modulation.…”

Effect of Long-Term Electrical Spinal Cord Stimulation on Expression of Non-Reciprocal Inhibition α-Motoneurons of Human Skeletal Muscles

“…В наших ранних исследованиях показано, что длительная чрескожная электрическая стимуляция спинного мозга (ЧЭССМ) в области T 11 -T 12 грудных позвонков повышает силовые возможности мышц-агонистов голени [1,2]. Одним из механизмов моторной системы, предохраняющим скелетные мышцы от чрезмерного напряжения (силы) и обеспечивающим координированные сокращения различных мышечных групп, является нереципрокное (аутогенное) торможение, которое осуществляется по афферентным волокнам Ib от сухожильных органов Гольджи на спинальные мотонейроны собственной мышцы и мышцы-синергисты, и находится под супраспинальным контролем [3][4][5][6]. Тем не менее, сведения о влиянии длительной ЧЭССМ на функцио-нальную активность нереципрокного торможения α-мотонейронов скелетных мышц человека до сих пор не изучены.…”