Effects of wrist flexion and extension on forearm supination force

DOI
  • OTAKI Ryoji
    Department of Occupational Therapy, Hatsudai Rehabilitation Hospital
  • SATO Toshiaki
    Department of Occupational Therapy, Faculty of Health Sciences, Yamagata Prefectural University of Health Sciences
  • NAGANUMA Makoto
    Department of Physical Therapy, Yamagata College of Medical Arts Sciences Department of Anatomy and Structural Science, Yamagata University Faculty of Medicine
  • SUZUKI Katsuhiko
    Department of Physical Therapy, Faculty of Health Sciences, Yamagata Prefectural University of Health Sciences
  • NARITA Aya
    Department of Orthopeadic Surgery, Yamagata University Faculty of Medicine Department of Anatomy and Structural Science, Yamagata University Faculty of Medicine
  • SATO Asato
    Department of Rehabilitation, Shonai Municipal Hospital
  • MIYASAKA Takuji
    Department of Acupancture & Moxa Cautery, Judo Therapy, Shinshu Institute of Altternative Medicine and Welfare
  • FUJII Hiromi
    Department of Occupational Therapy, Faculty of Health Sciences, Yamagata Prefectural University of Health Sciences
  • NAITO Akira
    Department of Anatomy and Structural Science, Yamagata University Faculty of Medicine

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Other Title
  • 手根の屈曲と伸展が前腕回外力に及ぼす効果

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Abstract

The musculus (m.) flexor carpi radialis (FCR) and m. extensor carpi radialis (ECR) act respectively as a forearm pronator and supinator in humans. This study examined effects of wrist flexion and extension on forearm supination force in eight normal human subjects. The forces produced by maximal supination with the wrist relaxed (R-Sup), maximally flexed (F-Sup), and maximally extended (E-Sup) were measured in forearm 90°(prone), 60° (P60°), 30° (P30°), and 0° pronated (neutral) positions. Electromyograms (EMG) of FCR, ECR, and m. biceps brachii (BB) were recorded. In the EMG study, FCR and ECR respectively showed activities during flexion and extension. The BB showed activities increasing concomitantly with increased force. Usually, E-Sup produced larger BB activities than R-sup and F-Sup; F-Sup decreased FCR activities and increased ECR activities. The force study showed that the respective forces of R-, F-, and E-Sup decreased with changing position from prone to neutral. Assuming the force of R-Sup in each position as 100%, those of E-Sup was 163±20% (mean ±S.D.), 142±17%, 134±15%, and 118±23%, and those of F-Sup was 81±7%, 90±14, 78±13%, and 80±10%, respectively, in the prone, P60°, P30°, and neutral positions. In every position, the force of E-Sup was larger and that of F-Sup was smaller than that of R-Sup. The increment of the force of E-Sup decreased with changing position from prone to neutral. The force study results suggest that the force is reinforced by extension and weakened by flexion, and that the reinforcement effect decreases with supination of the forearm. Spinal reflex arcs of facilitation from ECR to BB, inhibition between FCR and ECR, and inhibition from BB to FCR exist in humans. The EMG study results suggest that the effects result not only from muscle actions but also from reflex arc activation.

Journal

  • Structure and Function

    Structure and Function 8 (1), 13-18, 2009

    Co-medical Research Society of Structure and Function

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