The findings of this recent study from the University of Alberta in Canada correlate with our observations at Kinetic Konnections. When the feet function well, the reflexes triggered by ground contact with walking or sitting end up triggering muscles further up in the body to stabilize.
Another interesting insight from the research matches one of our key assessment points—the heel. We see poorly stabilizing heels do not enable initiation of stabilizing reactions up through the knee, hip, pelvis, core, etc. And a well stabilizing heel is efficient at initiating this chain reaction. The study showed that a tap applied at the heel (calcaneus) was 75-94% more efficient at triggering a response in the lower back muscles.
One of my colleagues, Physical Therapist, Theresa Eiden (CARE Physical Therapy in Chicago, IL) preaches the virtues of foot function to help back function. Her personal pick for footwear is the Vibram® five finger foot gloves. She finds they keep her back from becoming fatigued during a long day in the clinic. The minimalist footwear is a growing trend with runners as it encourages natural foot mechanics.
Below is the abstract and citation for the study. It is pretty hard core so approach with caution. Enjoy!
Exp Brain Res. 2009 Jun;196(2):217-27. Epub 2009 May 30.
Reflex pathways connect receptors in the human lower leg to the erector spinae muscles of the lower back. Clair JM, Okuma Y, Misiaszek JE, Collins DF. Human Neurophysiology Laboratory, Faculty of Physical Education and Recreation, Centre for Neuroscience, University of Alberta, E-488 Van Vliet Centre, AB, Canada.
Reflex pathways connect all four limbs in humans. Presently, we tested the hypothesis that reflexes also link sensory receptors in the lower leg with muscles of the lower back (erector spinae; ES). Taps were applied to the right Achilles’ tendon and electromyographic activity was recorded from the right soleus and bilaterally from ES. Reflexes were compared between sitting and standing and between standing with the eyes open versus closed. Reflexes were evoked bilaterally in ES and consisted of an early latency excitation, a medium latency inhibition, and a longer latency excitation. During sitting but not standing, the early excitation was larger in the ES muscle ipsilateral to the stimulation (iES) than in the contralateral ES (cES). During standing but not sitting, the longer latency excitation in cES was larger than in iES. This response in cES was also larger during standing compared to sitting. Responses were not significantly different between the eyes open and eyes closed conditions. Taps applied to the lateral calcaneus (heel taps) evoked responses in ES that were not significantly different in amplitude or latency than those evoked by tendon taps, despite a 75-94% reduction in the amplitude of the soleus stretch reflex evoked by the heel taps. Electrical stimulation of the sural nerve, a purely cutaneous nerve at the ankle, evoked ES reflexes that were not significantly different in amplitude but had significantly longer latencies than those evoked by the tendon and heel taps. These results support the hypothesis that reflex pathways connect receptors in the lower leg with muscles of the lower back and show that that the amplitude of these reflexes is modulated by task. Responses evoked by stimulation of the sural nerve establish that reflex pathways connect the ES muscles with cutaneous receptors of the foot. In contrast, the large volley in muscle spindle afferents induced by the tendon taps compared to the heel taps did not alter the ES responses, suggesting that the reflex connection between triceps surae muscle spindles and the ES muscles may be relatively weak. These heteronymous reflexes may play a role in stabilizing the trunk for maintaining posture and balance.