title: Slipping during side-step cutting: anticipatory effects and familiarization.
abstract: The aim of the present study was to verify whether the expectation of perturbations while performing side-step cutting manoeuvres influences lower limb EMG activity, heel kinematics and ground reaction forces. Eighteen healthy men performed two sets of 90° side-step cutting manoeuvres. In the first set, 10 unperturbed trials (Base) were performed while stepping over a moveable force platform. In the second set, subjects were informed about the random possibility of perturbations to balance throughout 32 trials, of which eight were perturbed (Pert, 10cm translation triggered at initial contact), and the others were "catch" trials (Catch). Center of mass velocity (CoMVEL), heel acceleration (HAC), ground reaction forces (GRF) and surface electromyography (EMG) from lower limb and trunk muscles were recorded for each trial. Surface EMG was analyzed prior to initial contact (PRE), during load acceptance (LA) and propulsion (PRP) periods of the stance phase. In addition, hamstrings-quadriceps co-contraction ratios (CCR) were calculated for these time-windows. The results showed no changes in CoMVEL, HAC, peak GRF and surface EMG PRE among conditions. However, during LA, there were increases in tibialis anterior EMG (30-50%) concomitant to reduced EMG for quadriceps muscles, gluteus and rectus abdominis for Catch and Pert conditions (15-40%). In addition, quadriceps EMG was still reduced during PRP (p<.05). Consequently, CCR was greater for Catch and Pert in comparison to Base (p<.05). These results suggest that there is modulation of muscle activity towards anticipating potential instability in the lower limb joints and assure safety to complete the task.
authors.affiliation: Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Anderson Souza Castelo
authors.initials: AS
authors.lastname: Oliveira
authors.affiliation: Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Priscila Brito
authors.initials: PB
authors.lastname: Silva
authors.affiliation: Department of Mechanical and Manufacturing Engineering, Aalborg University, Aalborg, Denmark.
authors.forename: Morten Enemark
authors.initials: ME
authors.lastname: Lund
authors.affiliation: Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany.
authors.forename: Dario
authors.initials: D
authors.lastname: Farina
authors.affiliation: Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark. Electronic address: uwek@hst.aau.dk.
authors.forename: Uwe Gustav
authors.initials: UG
authors.lastname: Kersting
mesh_terms: D000328:Adult; D059031:Anticipation, Psychological / Q000502:physiology*; D001696:Biomechanical Phenomena / Q000502:physiology; D004576:Electromyography; D006801:Humans; D007596:Joints / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D009949:Orientation / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D021641:Recognition, Psychology / Q000502:physiology*; D012420:Running / Q000502:physiology*
keywords: Anticipation; EMG; Kinematics; Side-step cutting; Slips