The purpose of this study was to determine the tibialis posterior (TP), peroneus longus (PL) and flexor digitorum longus (FDL) muscle activity change resulting from orthotic insertion during the walking stance phase by using a fine-wire and a surface electromyography (EMG).
Sixteen healthy male students participated in this study; participants who had injuries or surgical intervention for the lower extremities in the past year or had a neurological problem were excluded.
Bipolar fine-wire intramuscular electrodes were employed for measurement of TP and FDL muscle activity.
Gait tasks were performed under three conditions – barefoot, with footwear and with footwear plus orthoses.
Prefabricated orthoses were employed in this study because the authors considered it more clinically meaningful to see if easy and low-cost prefabricated orthoses could change the muscle activity pattern of the calf muscles.
The orthoses had three arch supports for the medial longitudinal, lateral longitudinal and transverse arches; these arch supports functioned to prevent from lowering the arches.
The force plate and EMG system were synchronised for simultaneous data collection; in each condition, participants were instructed to walk at comfortable speed on the walkway and to step on the force plate with the right foot during gait trials.
The findings of the study revealed that the orthoses significantly reduced muscle activity level of TP in midstance and propulsion phases during gait.
In contrast, muscle activity level of the PL and FDL remained the same for all conditions in each phase.
Reduction of TP muscle activity might be beneficial for patients who have excessive TP contraction related injuries such as medial tibial stress syndrome.
Further research is required to clarify the clinical effect of orthoses in patients with medial tibial stress syndrome.
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