Either Stepping or Standing


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People with motor complete spinal cord injury are unable to stand, walk or move their lower limbs voluntarily. In most subjects, natural recovery of those functions is most likely impossible. In the last few years there are been successful attempts at boosting the effect of rehabilitation by combining it with treatments such as epidural stimulation. Epidural stimulation somehow mimics the signals that the brain normally transmits to initiate movement. It is achieved by electrically stimulating the lower spinal cord to activate the neural circuits.

This boosting effect is in fact so powerful that properly trained individuals with their stimulator activated are able to voluntary control their legs and even stand unassisted. The next step of the study was to explore the possibility to achieve standing without the boosting effect of the stimulator and eventually to train the subjects to take steps.

What are the results of the study?
Doctor Susan Harkema, from University of Louisville (USA), was extensively training and testing the four subjects that were originally implanted with the stimulator. After undergoing an intense stand training, the ability to stand improved to different extents in the four participants. This improvement corresponds to a more constant contraction of the leg muscles.

The team went on performing the step training right afterwards and the result was that three of the four individuals saw their standing ability substantially impaired. This impairment was in fact so strong that it brought the individuals to perform as poorly as before they started their initial standing training. The step training somehow “erased” the progress made with the standing training. These results suggest that subjects can train to perform better in either one or the other task but not both at the same time.

Finally, both stand and step training with epidural stimulation were not sufficient to improve movements for standing when spinal stimulation was switched off.

What will happen next?
Since the stand and step training happened in a sequential manner (first one then the other) Doctor Harkema is suggesting to test new training protocols. One of the ideas is for example to interleave them. Both training will happen almost at the same time and in short alternating periods. Although unsuccessful in this first attempt, the goal of the team remains to improve both standing and stepping.

 

Source: Rejc E, Angeli CA, Bryant N, Harkema S. Effects of stand and step training with epidural stimulation on motor function for standing in chronic complete paraplegics. Journal of Neurotrauma. 2016 Aug 26.