Effect of foot orthotics on quadriceps and gluteus medius electromyographic activity during selected exercises

Hertel J, Sloss BR, Earl JE. Effect of foot orthotics on quadriceps and gluteus medius electromyographic activity during selected exercises. To compare electromyographic activity of the vastus medialis, vastus lateralis, and gluteus medius during functional activities in subjects with different foot types while wearing various off-the-shelf foot orthotics. Experimental, controlled; 3 foot-type groups (pes planus, pes cavus, pes rectus) each tested in 4 orthotic conditions while performing 3 different exercises. Laboratory. Thirty healthy young adults, 10 with each foot type. Four conditions: no orthotic, 7° medial rearfoot post, 4° lateral rearfoot post, and neutral rearfoot post. Surface electromyographic activity for the vastus medialis, vastus lateralis, and gluteus medius during single-leg squatting, lateral stepdown, and maximum vertical jump exercises. Greater vastus medialis and gluteus medius activity was found with all 3 orthotic conditions, regardless of subject foot type, during the single-leg squat and lateral stepdown. Less vastus lateralis activity was found with the vertical jump with all orthotic conditions, again regardless of foot type. During slow controlled exercises such as the single-leg squat and lateral stepdown, vastus medialis and gluteus medius activity may be enhanced with an off-the-shelf orthotic, regardless of posting or foot type. These same findings do not appear to carry over to a more explosive task such as the maximal vertical jump.