Speed, resistance, and unexpected accelerations modulate feed forward and feedback control during a novel weight bearing task

Shih Chiao Tseng, Keith R. Cole, Michael A. Shaffer, Michael A. Petrie, Chu Ling Yen, Richard K. Shields

Research output: Contribution to journalArticlepeer-review


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 0.6 Hz) 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.

Original languageEnglish (US)
Pages (from-to)345-353
Number of pages9
JournalGait and Posture
StatePublished - Feb 1 2017
Externally publishedYes


  • Feedback
  • Force perturbation
  • Long-latency reflex
  • Neuromuscular control
  • Visuomotor

ASJC Scopus subject areas

  • Biophysics
  • Orthopedics and Sports Medicine
  • Rehabilitation


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