Physiological tremor reveals how thixotropy adapts skeletal muscle for posture and movement

Carlijn Vernooij, Raymond Reynolds, Martin Lakie

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)
247 Downloads (Pure)


People and animals can move freely, but they must also be able to stay still. How do skeletal muscles economically produce both movement and posture? Humans are well known to have motor units with relatively homogeneous
mechanical properties. Thixotropic muscle properties can provide a solution by providing a temporary stiffening of all skeletal muscles in postural conditions. This stiffening is alleviated almost instantly when muscles start to move. In
this paper, we probe this behaviour. We monitor both the neural input to a muscle, measured here as extensor muscle electromyography (EMG), and its output, measured as tremor (finger acceleration). Both signals were analysed continuously as the subject made smooth transitions between posture and
movement. The results showed that there were marked changes in tremor which systematically increased in size and decreased in frequency as the subject moved faster. By contrast, the EMG changed little and reflected muscle force requirement rather than movement speed. The altered tremor reflects naturally occurring thixotropic changes in muscle behaviour. Our results
suggest that physiological tremor provides useful and hitherto unrecognized insights into skeletal muscle’s role in posture and movement.
Original languageEnglish
Article number160065
JournalRoyal Society Open Science
Issue number5
Publication statusPublished - 1 May 2016


  • physiological tremor
  • mechanical resonance
  • thixotropy
  • posture
  • electromyography
  • muscle


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