When looking at the human body holistically, we tend to respect the fact that the different systems work together to allow what is possible. This is what makes this study quite interesting (https://www.ncbi.nlm.nih.gov/pubmed/24103912).
Researchers wanted to know if it was possible to improve the function of the lower limbs after sectioning the spinal cord, by activating the upper limbs.
This study performed on rats is promising. Once the spinal cord sectioned, they conditioned the upper limb in order to increase function of the lower limb. It worked. We saw an improvement in spinal circuits. They were more excitable.
What’s more, electrophysiological studies demonstrated the improvement of the lower limbs on a treadmill when the upper limbs were utilized simultaneously. We did not see the same improvement when the upper limbs were not utilized.
If it’s true that this realization can have an impact on rehabilitation strategies for certain extreme conditions, one can think that if we want to improve performance in sports, where running, for example, is an important component, we could possibly assess and improve how we crawl, walk on all four and walk!