title: Assessment of the ankle muscle co-contraction during normal gait: a surface electromyography study.
abstract: The study was designed to assess the co-contractions of tibialis anterior (TA) and gastrocnemius lateralis (GL) in healthy young adults during gait at self-selected speed and cadence, in terms of variability of onset-offset muscular activation and occurrence frequency. Statistical gait analysis (SGA), a recent methodology performing a statistical characterization of gait by averaging spatio-temporal and EMG-based parameters over numerous strides, was performed in twenty-four healthy young adults. Co-contractions were assessed as the period of overlap between activation intervals of TA and GL. Results showed that GL and TA act as pure agonist/antagonists for ankle plantar/dorsiflexion (no co-contractions) in only 21.3 ± 8.2% of strides. In the remaining strides, statistically significant (p < 0.05) co-contractions appear in early stance (29.2 ± 1.7%), mid-stance (32.1 ± 18.3%) and swing (62.2 ± 2.0%). This significantly increased complexity in muscle recruitment strategy beyond the activation as pure ankle plantar/dorsiflexors, suggests that co-contractions are likely functional to further physiological tasks as foot inversion, balance improvement, control of ankle stability and knee flexion. This study represents the first attempt for the development in healthy young adults of a "normality" reference frame for GL/TA co-contractions, able to include the physiological variability of the phenomenon and eliminate the confounding effect of age.
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, 60131 Ancona, Italy. Electronic address: f.dinardo@univpm.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Di Nardo
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, 60131 Ancona, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Mengarelli
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, 60131 Ancona, Italy; Posture and Movement Analysis Laboratory, Italian National Institute of Health and Science on Aging (INRCA), 60131 Ancona, Italy.
authors.forename: Elvira
authors.initials: E
authors.lastname: Maranesi
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, 60131 Ancona, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Burattini
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, 60131 Ancona, Italy.
authors.forename: Sandro
authors.initials: S
authors.lastname: Fioretti
mesh_terms: D000328:Adult; D000842:Ankle / Q000502:physiology*; D000843:Ankle Joint / Q000502:physiology; D004576:Electromyography / Q000379:methods*; D005260:Female; D005528:Foot / Q000502:physiology; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D055815:Young Adult
keywords: Ankle-flexor muscles; Antagonist muscles; Statistical gait analysis; sEMG