The Efficacy of Two Methods of Ankle Immobilization in Reducing Gastrocnemius,Soleus,and Peroneal Muscle Activity during Stance Phase of Gait

Abstract

Background:

Immobilization to limit muscle activity is a common therapeutic and posttreatment event. There are potential time and resource savings if a prefabricated boot can replace a custom applied cast. The purpose of this study was to determine if muscle activity reduction is similar using a fiberglass cast versus a prefabricated (Aircast FoamWalker) boot.

Methods:

Surface EMG data were recorded from the gastrocnemius, soleus, and peroneals of 12 normal adults while walking barefoot, in a fiberglass cast with a cast shoe (cast), and while wearing an Aircast FoamWalker (boot). Subjects walked at their self-selected speed for 10 trials in each condition, and the order of barefoot, cast, and boot was randomly assigned. The data were rectified, integrated across stance phase and normalized to a percent of each subject's barefoot mean integrated EMG (iEMG) value. For each muscle, a linear mixed-effects statistical model (subject by trial by condition) was utilized to determine if iEMG activity levels were reduced by immobilization compared to barefoot walking.

Results:

Activity for all muscles was significantly lower in the boot compared with barefoot (p <.05). The cast iEMG levels were significantly different from barefoot for the soleus and peroneals (p <.05). Gastrocnemius activity was significantly decreased in the boot when compared with the cast (p <.0001). The greater reduction in iEMG levels for the boot indicates that it is superior to a fiberglass cast in reducing gastrocnemius muscle activity during the stance phase of gait.

Conclusions:

The data show that a prefabricated boot is as effective as a custom applied cast in reducing soleus and peroneal muscle iEMG during stance phase. The boot was more effective in reducing gastrocnemius activity when compared to the cast.

Clinical Relevance:

This study suggests that a prefabricated boot may be used in place of a custom cast when the goal of treatment is to limit muscle activity of the leg.