The history of foot ulceration does not change lower leg EMG activity during shod gait in diabetic neuropathy

Paula Marie Hanai Akashi
Dep. Physical Therapy, University of Sao Paulo

Isabel de Camargo Neves Sacco
Dep. Physical Therapy, University of Sao Paulo

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     Last modified: February 26, 2007

Abstract
The purpose of this study was to investigate the influence of diabetic neuropathy and history of plantar ulcers in electromyography activity of thigh and calf muscles during shod gait using habitual shoes. This study involved 45 adults divided into three groups: control group (CG;n=16), diabetic neuropathic group (DG;n=19) and diabetic neuropathic group with previous history of plantar ulceration (UDG;n=10). All neuropathic subjects were diagnosed by physicians. The electrical activity of the right vastus lateralis (VL), gastrocnemius lateralis (GL) and tibialis anterior (TA) were studied during stance phase of a self selected cadence gait. The bipolar surface electrodes were placed according to SENIAM recommendations. Electromyography was collected simultaneously with the ground reaction force (GRF), which was used to synchronize and to determine the stance phase of each subject. The EMG variables calculated from the linear envelopes curves were: the maximum peaks and time of peak occurrence for TA, VL and GL muscles, and a co-activation index calculated by the ratio between TA and GL IEMG. Inter-groups comparisons of electromyographic variables were made using two MANOVAs (peaks and times) and one ANOVA-one way for the co-activation index between the TA and GL. An <0.05 was adopted. UDG presented the time of GL peak occurance delayed in comparison to CG (CG=65,56?3,95;DG= 67,32?3,33;UDG=70,20?4,87; p=0,02). The co-activation index was significantly higher in CG in comparison to both diabetic groups (CG=0,97?0,04;DG=0,94?0,03;UDG=0,93?0,04; p=0,02). There were no other statistical differences. The delayed activity of GL on the UDG could be an indicative of a propulsion inefficacy in diabetic neuropathic subjects with worse clinical history represented by the plantar ulcers occurrence. This alteration could be responsible to the lower ankle extensor moments on push-off phase in neuropathic subjects, which is already described in the literature. The higher co-activation index in the CG subjects indicates a better ankle stability of healthy subjects when compared to diabetic neuropathic subjects. Although they showed smaller co-activation mechanisms and a probable deficit of the propulsion mechanisms, which could compromise their ability to walk, the diabetic subjects didn?t present any changes in the activity of the muscles responsible for load attenuation during the initial contact of the foot with the floor (TA and VL), which is described in the literature as one of the mechanisms to avoid foot ulceration. Muscle activity mechanisms to load attenuation did not occur when diabetic neuropathic subjects walk with their habitual shoes, once its use attenuates loads in diabetic foot.