Mechanisms contributing to reduced knee stiffness during movement

Daniel Ludvig*, Maciej Plocharski, Piotr Plocharski, Eric J. Perreault

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


The ability to modulate the mechanical properties of our limbs contributes to our ability to interact with the physical world in a consistent and predictable manner. An individual joint’s contributions to whole limb mechanics can be quantified by its joint impedance, which characterizes the torque generated about a joint in response to external perturbations of position. A number of studies have estimated joint impedance during movement and have shown that it can be much lower than it is during posture. However, the mechanisms contributing to these differences remain unknown partly because conditions known to affect impedance, including muscle activation and joint angles, have not been carefully controlled across studies. The goal of this study was to contrast knee impedance during continuous volitional movements with that during maintained postures spanning a similar range of joint angles and muscle activations and to explore physiological mechanisms likely to contribute to the observed differences. We found that knee impedance was substantially lower during movement than during matched postural tasks, even for matched muscle activations. At times, the impedance during movement was even lower than that measured during isometric tasks with no volitional muscle activity. These decreases in impedance could be attributed in part to reduced stretch reflexes during movement and to an effect of movement itself on reducing knee impedance.

Original languageEnglish (US)
Pages (from-to)2959-2970
Number of pages12
JournalExperimental Brain Research
Issue number10
StatePublished - Oct 1 2017


  • Knee impedance
  • Movement
  • Posture
  • Reflex
  • Stiffness

ASJC Scopus subject areas

  • Neuroscience(all)


Dive into the research topics of 'Mechanisms contributing to reduced knee stiffness during movement'. Together they form a unique fingerprint.

Cite this