Touch a hot plate and your arm immediately withdraws before you feel the pain. This withdrawal reflex is protective and faster than the brain issuing a pain response and then moving which would be a much more damaging scenario.
The withdrawal reflex occurs through the spine and does not need to get the interpreting complexities of the brain involved. The brain can however override the reflex – have you ever held onto a hot cup of coffee for just a little longer while you got it to the table to avoid spilling it. That was you overriding the reflex momentarily.
So what does this have to do with the previous post on balance?
When balancing in a standing position the ankle is the primary stabilising joint, closely followed by the hip. It is just not feasible for the brain to control the ankle with a barrage of micro-motor commands. It would be too slow and you would probably fall over too often.
Instead there are strong connections or reflex couplings between the force sensors of the feet and the muscles of the ankle that travel via the spinal cord and serve to modulate the contractions of the muscles around the ankle. This short-loop feedback mechanism emphasises the importance of not blocking the sensory inflow from the feet and how doing so could affect balance and gait performance. We are heading for barefoot territory here!
This post was not intended to promote going barefoot – but it has inadvertently done so. My initial aim was to just put down some thoughts on this study by Fallon et al (2005) and to highlight the fact that it’s not all about the brain when it comes to movement.
It seems any sensory ‘wake and shake’ for our sole is good for keeping us balanced.
When we consider the dysfunctional muscle firing patterns that occur alongside so many ankle region pathologies it is plausible to consider the foot-ankle reflexes as influential to successful rehabilitation.
How would you apply this in clinic?
Reference: McNulty, P. A., Türker, K. S., & Macefield, V. G. (1999). Evidence for strong synaptic coupling between single tactile afferents and motoneurones supplying the human hand. The Journal of physiology, 518 ( Pt 3)(Pt 3), 883–893. https://doi.org/10.1111/j.1469-7793.1999.0883p.x