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

• MASS and FCO orthoses are unable to control rearfoot or forefoot motion.
• The positioning of the first ray by the orthotics did not affect hallux motion.
• Orthotics did not have a significant effect on EMG activity during stance.

BackgroundPersons 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.Methods52 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.ResultsAn 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.ConclusionOrthoses 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.