title: Muscle co-contraction around the knee when walking with unstable shoes.
abstract: Walking with unstable shoes has been discussed to decrease joint loading. Typical estimates of joint loading using an inverse dynamic approach only account for net joint moments, not considering the potential role of muscular co-contraction. Therefore, the purpose of this study was to compare muscular co-contraction levels when walking with two different unstable shoe constructions (rocker-bottom and toning shoes) compared to walking with regular shoes. For each shoe condition, 12 healthy subjects walked with both, a regular shoe and with an unstable shoe at self-selected walking speed at a 10-m walkway. Surface EMG data of selected muscles were recorded and time normalized for calculating co-contraction indices (CCI) for opposing muscle groups. Results showed an increase of co-contraction primarily for vastii and gastrocnemius muscles for the first and second half of stance when walking with an unstable shoe construction. Therefore, when using an inverse dynamic approach to analyze joint loading differences between regular shoes and unstable shoes, one should be cautious in interpreting the data, as these methods base their estimates of joint moments upon the net joint torque.
authors.affiliation: Department of Physiotherapy, St. Poelten University of Applied Sciences, St. Poelten, Austria; Institute for Sciences and Services in Health, St. Poelten University of Applied Sciences, St. Poelten, Austria. Electronic address: brian.horsak@fhstp.ac.at.
authors.forename: Brian
authors.initials: B
authors.lastname: Horsak
authors.affiliation: Department of Biomechanics, Kinesiology and Applied Computer Science, University of Vienna, Vienna, Austria.
authors.forename: Mario
authors.initials: M
authors.lastname: Heller
authors.affiliation: Department of Biomechanics, Kinesiology and Applied Computer Science, University of Vienna, Vienna, Austria.
authors.forename: Arnold
authors.initials: A
authors.lastname: Baca
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D005684:Gait; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology; D012775:Shoes; D016138:Walking / Q000502:physiology*
keywords: Biomechanics; Co-contraction index; Electromyography; Gait analysis; Toning shoes; Unstable shoes