Abstract
High plantar flexor moment during the stance phase is known to cause high plantar pressure under the forefoot; however, the effects on plantar pressure due to a change of gastrocnemius medialis (GM) activity during gait, have not been investigated to date. Reciprocal inhibition is one of the effects of electrical stimulation (ES), and is the automatic antagonist alpha motor neuron inhibition which is evoked by excitation of the agonist muscle. The aim of this study was to investigate the influences of ES of the tibialis anterior (TA) on plantar pressure and the GM activity during gait in healthy adults. ES was applied to the TAs of twenty healthy male adults for 30 minutes at the level of intensity that causes a full range of dorsiflexion in the ankle (frequency; 50 Hz, on-time; 10 sec, off-time; 10 sec). Subjects walked 10 meters before and after ES, and we measured the peak plantar pressure (PP), pressure time integral (PTI), and gait parameters by using an F-scan system. The percentage of integrated electromyogram (%IEMG), active time, onset time, peak time, and cessation time of TA and GM were calculated. PP and PTI under the forefoot, rear foot, and total plantar surface significantly decreased after the application of ES. Meanwhile, changes of gait parameters were not observed. %IEMG and the active time of both muscles did not change; however, onset time and peak time of GM became significantly delayed. ES application to the TA delayed the timing of onset and peak in the GM, and caused the decrease of plantar pressure during gait. The present results suggest that ES to the TA could become a new method for the control of plantar pressure via modulation of GM activity during gait.
Highlights
IntroductionHigh plantar pressure caused by foot deformities (e.g. hammer or claw toe, hallux valgus, bony prominences and/or Charcot arthropathy) and limited ankle dorsiflexion range of motion (ROM) are risk factors for the formation of callosities on the plantar surface [1,2]
High plantar pressure caused by foot deformities and limited ankle dorsiflexion range of motion (ROM) are risk factors for the formation of callosities on the plantar surface [1,2]
We found that the regulation of gastrocnemius medialis (GM) activity occurred by application of electrical stimulation (ES) to the tibialis anterior (TA), in addition to the appearance of a suppressive effect on plantar pressure during gait, in healthy male adults
Summary
High plantar pressure caused by foot deformities (e.g. hammer or claw toe, hallux valgus, bony prominences and/or Charcot arthropathy) and limited ankle dorsiflexion range of motion (ROM) are risk factors for the formation of callosities on the plantar surface [1,2]. In patients with peripheral neuropathy, the lack of a protective sensation that results from this condition leads to unattended minor injuries caused by repetitive excess plantar pressure via callosities [4]. The presentation of patients with diabetic peripheral neuropathy (DPN) is characterized by an increase of plantar pressure caused by several structural alterations, autonomic, sensory, and motor deficits [8,9]. Footwear is effective in the prevention of a recurrent foot ulcer [11], and the combination of a low peak pressure with footwear (< 200 kPa) and high adherence (> 80%) can reduce risk of ulcer recurrence by more than 50% [11]. A new intervention combined with therapeutic footwear can relieve plantar pressure despite low adherence of footwear, resulting in the decrease of risk for recurrence
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