The effect of orthotics on intersegmental foot kinematics and the EMG activity of select lower leg muscles.

ABSTRACT

BACKGROUND: Persons with exertional related leg pain are managed using orthoses. This study aimed to determine the effectiveness of two orthoses in altering foot motion and muscle activity in symptomatic individuals. METHODS: 52 subjects with lower extremity pain complaints of a non-traumatic, mechanical origin received one of two orthoses. Foot kinematics and EMG activity were recorded while treadmill walking in 3 footwear conditions. The peak EMG activity of the sandal and sandal orthotic trials (normalized to peak barefoot values) and foot motion during 4 subphases of stance were obtained. Using a multivariate multilevel model via linear mixed models, the effect of orthoses within these phases on motion and EMG was determined. RESULTS: An effect of orthotic type was not present for any of the rearfoot or forefoot motions (p>.10). A significant effect of footwear and orthotic type on first ray motion (p<.05) during subphases 2 and 4 was seen. During subphase 4 an interaction effect between footwear condition and orthotic type on tibialis posterior EMG activity (p=.036) was present. CONCLUSION: Orthoses are unable to control rear or midfoot motion but appear to control first ray motion and during late stance, affect tibialis posterior muscle activity. Public trials registry number NCRT02143947.