Abstract
Interventions for strengthening intrinsic foot muscles may be beneficial for rehabilitation
from overuse injuries. In this study the acute effects of high-frequency, low-intensity
wide-pulse electrical stimulation (WPS) over an intrinsic muscle on subsequent foot
function during walking was assessed in healthy participants. WPS was delivered to
the m. abductor hallucis (m.AH) of the non-dominant foot during relaxed standing. 3-dimensional forefoot (FF)
– rearfoot (RF) coordination was quantified with a vector coding technique within
separate periods of the stance phase to study WPS functional effects on foot motion.
4 types of coordinative strategies between the FF and RF were interpreted and compared
PRE-to-POST-WPS for both the experimental and control feet. Bilateral electromyography
(EMG) from m.AH was analysed during the intervention period for evidence of acute neuromuscular
adaptation. The results showed that WPS significantly modulated FF-RF coordination
during mid-stance, indicative of a more stable foot. Specifically, a statistically
significant increase in FF eversion with concomitant RF inversion in the frontal plane
and RF-dominated adduction in the transverse plane was observed. Subject-specific
increases in post-stimulus m.AH EMG activation were observed but this was not reflected in an overall group effect.
It is concluded that the structural integrity of the foot during walking is enhanced
following an acute session of WPS and that this mechanical effect is most likely due
to stimulation induced post-tetanic potentiation of synaptic transmission.
Key words
rehabilitation - wide-pulse electrical stimulation - foot - kinematic coupling - post-tetanic
potentiation
