Estimation of musculotendon kinematics under controlled tendon indentation

Matthieu K. Chardon*, Yasin Y. Dhaher, Nina I. Suresh, Giselle Jaramillo, W. Zev Rymer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The effects of tendon indentation on musculotendon unit mechanics have been left largely unexplored. Tendon indentation is however routinely used in the tendon reflex exam to diagnose the state of reflex pathways. Because muscle mechanoreceptors are sensitive to mechanical changes of the musculotendon unit, this gap in knowledge could potentially impact our understanding of these neurological exams. Accordingly, we have used ultrasound (US) imaging to compare the effects of tendon indentation with the effects angular rotation of the elbow in six neurologically intact individuals. We used sagittal ultrasound movies of the biceps brachii to compare length changes induced by each of these perturbations. Length changes were quantified using a pixel-tracking protocol.Our results show that a 20. mm indentation of the distal tendon is broadly equivalent to a 15° elbow rotation. We also show that within the imaging window the strain differences between the two stretching protocols are statistically insignificant. Finally, we show that there exists a significant linear relationship between the two stretching techniques and that this relationship spans a large rotational angle to indentation depth. We have used a novel tendon probe to administer controlled tendon indentations as a way to characterize musculotendon kinematics. Using this probe, we confirm that tendon indentation can be physiologically equated with joint rotation, and can thus be used as an input for muscle stretching protocols. Furthermore, this is potentially a simpler and more practical alternative to externally imposed angular joint motion.

Original languageEnglish (US)
Pages (from-to)3568-3576
Number of pages9
JournalJournal of Biomechanics
Issue number13
StatePublished - Oct 15 2015


  • Joint rotation
  • Kinematics
  • Musculotendon unit
  • Skeletal muscle stretch
  • Tendon indentation

ASJC Scopus subject areas

  • Biophysics
  • Rehabilitation
  • Biomedical Engineering
  • Orthopedics and Sports Medicine


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