Spinal interneuronal networks linking the forelimbs and hindlimbs

Do the intimate relationships of the upper limbs and lower limbs suggest that quadrupedal skill sets, if not true quadrupedal gait, were a piece of our past locomotion strategies ?  Or is it just representative of the close linkages for gait efficiency? Or maybe both?

In this study below the researchers pondered whether lower limb motor function can be improved after a spinal cord lesion by re-engaging functional activity of the upper limbs. Although this study looked at spinal cord hemisections in adult rats we know there is likely human correlation. This study showed improved hindlimb function when the forelimbs were engaged simultaneously with the hindlimbs during treadmill step-training as opposed to training only the hindlimbs.
As we have proposed here on the gait guys blog many times previously, this study’s results provide strong evidence that actively engaging the forelimbs improves hindlimb function and that one likely mechanism underlying these effects is the reorganization and re-engagement of rostrocaudal spinal interneuronal networks.
“For the first time, we provide evidence that the spinal interneuronal networks linking the forelimbs and hindlimbs are amenable to a rehabilitation training paradigm. Identification of this phenomenon provides a strong rationale for proceeding toward preclinical studies for determining whether training paradigms involving upper arm training in concert with lower extremity training can enhance locomotor recovery after neurological damage.”

This likely has huge implications in rehab measures and gait retraining for those who are not spinal cord impaired as well.  We have discussed many times that making a single limb change merely because the observer/clinician does not like the functional appearance of a limb is a  mistake most of the time. That what we see is a compensation, not the problem.  Go back and review our many “arm swing” blog posts, you should recall that the arms can have a huge impact on the leg function and that many times the arms take their cues from the lower limbs during gait.  This is a topic we have hammered many times in many blog posts and in many courses we have taught.  It is nice to see the literature continue to support the close relationships of the 4 limbs on a neurologic level.

Brain. 2013 Nov;136(Pt 11):3362-77. doi: 10.1093/brain/awt265. Epub 2013 Oct 7.

Use of quadrupedal step training to re-engage spinal interneuronal networks and improve locomotor function after spinal cord injury.

Shah PK1, Garcia-Alias G, Choe J, Gad P, Gerasimenko Y, Tillakaratne N, Zhong H, Roy RR, Edgerton VR.