Isometric Force Pillow: Using Air Pressure to Quantify Involuntary Finger Flexion in the Presence of Hypertonia

Caitlyn E. Seim*, Chuzhang Han, Alexis J. Lowber, Claire Brooks, Marie Payne, Maarten G. Lansberg, Kara E. Flavin, Julius P.A. Dewald, Allison M. Okamura

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapter


Survivors of central nervous system injury commonly present with spastic hypertonia. The affected muscles are hyperexcitable and can display involuntary static muscle tone and an exaggerated stretch reflex. These symptoms affect posture and disrupt activities of daily living. Symptoms are typically measured using subjective manual tests such as the Modified Ashworth Scale; however, more quantitative measures are necessary to evaluate potential treatments. The hands are one of the most common targets for intervention, but few investigators attempt to quantify symptoms of spastic hypertonia affecting the fingers. We present the isometric force pillow (IFP) to quantify involuntary grip force. This lightweight, computerized tool provides a holistic measure of finger flexion force and can be used in various orientations for clinical testing and to measure the impact of assistive devices.

Original languageEnglish (US)
Title of host publicationBiosystems and Biorobotics
PublisherSpringer Science and Business Media Deutschland GmbH
Number of pages6
StatePublished - 2022

Publication series

NameBiosystems and Biorobotics
ISSN (Print)2195-3562
ISSN (Electronic)2195-3570


  • Hypertonia
  • Measurement
  • Quantify
  • Spasticity
  • Stroke
  • Tool

ASJC Scopus subject areas

  • Biomedical Engineering
  • Mechanical Engineering
  • Artificial Intelligence


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