Leg stiffness adjustment for a range of hopping frequencies in humans

Hiroaki Hobara, Koh Inoue, Tetsuro Muraoka, Kohei Omuro, Masanori Sakamoto, Kazuyuki Kanosue

Research output: Contribution to journalArticle

77 Citations (Scopus)

Abstract

The purpose of the present study was to determine how humans adjust leg stiffness over a range of hopping frequencies. Ten male subjects performed in place hopping on two legs, at three frequencies (1.5, 2.2, and 3.0 Hz). Leg stiffness, joint stiffness and touchdown joint angles were calculated from kinetic and/or kinematics data. Electromyographic activity (EMG) was recorded from six leg muscles. Leg stiffness increased with an increase in hopping frequency. Hip and knee stiffnesses were significantly greater at 3.0 Hz than at 1.5 Hz. There was no significant difference in ankle stiffness among the three hopping frequencies. Although there were significant differences in EMG activity among the three hopping frequencies, the largest was the 1.5 Hz, followed by the 2.2 Hz and then 3.0 Hz. The subjects landed with a straighter leg (both hip and knee were extended more) with increased hopping frequency. These results suggest that over the range of hopping frequencies we evaluated, humans adjust leg stiffness by altering hip and knee stiffness. This is accomplished by extending the touchdown joint angles rather than by altering neural activity.

Original languageEnglish
Pages (from-to)506-511
Number of pages6
JournalJournal of Biomechanics
Volume43
Issue number3
DOIs
Publication statusPublished - 2010 Feb 10

Keywords

  • Ground reaction force
  • Joint stiffness
  • Leg spring
  • Lower extremity

ASJC Scopus subject areas

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

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