title: Speed, resistance, and unexpected accelerations modulate feed forward and feedback control during a novel weight bearing task.
abstract: We developed a method to investigate feed-forward and feedback movement control during a weight bearing visuomotor knee tracking task. We hypothesized that a systematic increase in speed and resistance would show a linear decrease in movement accuracy, while unexpected perturbations would induce a velocity-dependent decrease in movement accuracy. We determined the effects of manipulating the speed, resistance, and unexpected events on error during a functional weight bearing task. Our long term objective is to benchmark neuromuscular control performance across various groups based on age, injury, disease, rehabilitation status, and/or training. Twenty-six healthy adults between the ages of 19-45 participated in this study. The study involved a single session using a custom designed apparatus to perform a single limb weight bearing task under nine testing conditions: three movement speeds (0.2, 0.4, and 0.6Hz) in combination with three levels of brake resistance (5%, 10%, and 15% of individual's body weight). Individuals were to perform the task according to a target with a fixed trajectory across all speeds, corresponding to a∼0 (extension) to 30° (flexion) of knee motion. An increase in error occurred with speed (p<0.0001, effect size (eta2): η2=0.50) and resistance (p<0.0001, η2=0.01). Likewise, during unexpected perturbations, the ratio of perturbed/non-perturbed error increased with each increment in velocity (p<0.0014, η2=0.08), and resistance (p<0.0001, η2=0.11). The hierarchical framework of these measurements offers a standardized functional weight bearing strategy to assess impaired neuro-muscular control and/or test the efficacy of therapeutic rehabilitation interventions designed to influence neuromuscular control of the knee.
authors.affiliation: Department of Physical Therapy & Rehabilitation Science, University of Iowa Carver College of Medicine, 1-252 MEB, Iowa City, IA, 52242, United States.
authors.forename: Shih-Chiao
authors.initials: SC
authors.lastname: Tseng
authors.affiliation: Department of Physical Therapy & Rehabilitation Science, University of Iowa Carver College of Medicine, 1-252 MEB, Iowa City, IA, 52242, United States.
authors.forename: Keith R
authors.initials: KR
authors.lastname: Cole
authors.affiliation: Department of Physical Therapy & Rehabilitation Science, University of Iowa Carver College of Medicine, 1-252 MEB, Iowa City, IA, 52242, United States.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Shaffer
authors.affiliation: Department of Physical Therapy & Rehabilitation Science, University of Iowa Carver College of Medicine, 1-252 MEB, Iowa City, IA, 52242, United States.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Petrie
authors.affiliation: Department of Physical Therapy & Rehabilitation Science, University of Iowa Carver College of Medicine, 1-252 MEB, Iowa City, IA, 52242, United States.
authors.forename: Chu-Ling
authors.initials: CL
authors.lastname: Yen
authors.affiliation: Department of Physical Therapy & Rehabilitation Science, University of Iowa Carver College of Medicine, 1-252 MEB, Iowa City, IA, 52242, United States. Electronic address: richard-shields@uiowa.edu.
authors.forename: Richard K
authors.initials: RK
authors.lastname: Shields
mesh_terms: D000054:Acceleration; D000328:Adult; D004576:Electromyography; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009068:Movement; D016059:Range of Motion, Articular; D012016:Reference Values; D013647:Task Performance and Analysis; D016474:Weight-Bearing; D055815:Young Adult
keywords: Feedback; Force perturbation; Long-latency reflex; Neuromuscular control; Visuomotor