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Effects of wrist position and contraction on wrist flexors H-reflex, and its functional implications.

Authors
  • Chen, Fen-Fen
  • Lo, Sui-Foon
  • Meng, Nai-Hsin
  • Lin, Chien-Lin
  • Chou, Li-Wei
Type
Published Article
Journal
Journal of Electromyography and Kinesiology
Publisher
Elsevier
Publication Date
Oct 01, 2006
Volume
16
Issue
5
Pages
440–447
Identifiers
PMID: 16289712
Source
Medline
License
Unknown

Abstract

In order to determine whether joint position exerts a powerful influence on length-tension regulation in multiarticulate wrist flexors, three wrist positions (neutral, flexion and extension) and four levels of flexor contraction [0%, 10%, 20% and 30% maximum voluntary contraction (MVC)] were manipulated. There were significant differences in H-reflex amplitudes according to wrist positions and levels of flexor contraction. H-reflex increased linearly as a function of contraction in all three wrist positions. H-reflex was consistently larger in the wrist flexion than in the wrist extension position. The strength of the relationship (omega2) indicated that wrist position had a greater effect on H-reflex than force of muscle contraction. The interaction between wrist flexors contraction and joint position was significant only in the wrist flexion position. Trend analysis showed that, in the wrist flexion position, a low level of contraction was sufficient to maximally facilitate the H-reflex; however, a quadratic component was seen at higher contraction levels. The above findings may reflect the length-tension relationship of the multiarticulate wrist flexors. Therefore, this paper will discuss the functional implications related to the larger H-reflex in flexion position and the depressed H-reflex in the wrist extension position.

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