Plantar feedback contributes to the regulation of leg stiffness.
BACKGROUND
Running and hopping involve moving in a bouncing fashion during which the limbs behave as springs. The ability to alter the stiffness of these leg springs is essential to maintaining an efficient gait. Since the plantar surface of the foot is the only part of the body to encounter the ground during bipedal locomotion, it would seem logical that some aspect of the neurological functioning of the foot is responsible for transmission of information about the surface characteristics to the central nervous system, resulting in changes in leg stiffness.


METHODS
Ten subjects (9 males, 1 female) participated in this experiment. Lidocaine was injected inferior and posterior to the lateral malleolus in order to achieve tibial nerve block at the level of the ankle. Subjects hopped at 2.2 Hz on a force plate while data were collected at 1000 Hz. Data were analyzed for peak force and leg stiffness and compared using a repeated measures ANOVA.


RESULTS
Tactile sensation, deep pressure sensation, and abductor hallucis activity displayed significant decreases following the injection, as did postural stability. Subjects demonstrated a significantly decreased leg stiffness after the nerve block (P<.01).


CONCLUSIONS
Plantar sensation has an effect on regulating leg mechanics in hopping. A loss of sensation in this region can exert a significant impact on the properties of the leg in gait, and future research should determine the specific pathways by which plantar feedback exerts this effect.
Fiolkowski
Paul
P
Gemini Research Consulting, 499 Granite Terrace, Springfield, PA 19064, United States. pfiolkowski@yahoo.com
Bishop
Mark
M
Brunt
Denis
D
Williams
Blaise
B
D000328:Adult; D000704:Analysis of Variance; D000779:Anesthetics, Local / Q000008:administration & dosage; D001696:Biomechanical Phenomena; D005246:Feedback; D005260:Female; D005528:Foot / Q000502:physiology*; D006801:Humans; D007866:Leg / Q000502:physiology*; D008012:Lidocaine / Q000008:administration & dosage; D008297:Male; D009068:Movement / Q000502:physiology*; D009407:Nerve Block / Q000379:methods; D013979:Tibial Nerve
D000779:Anesthetics, Local; D008012:Lidocaine