Enhanced stretch reflex excitability in the soleus muscle during passive standing posture in humans

Shimba, Sachio; Kawashima, Noritaka; Ohta, Yuji; Yamamoto, Shin-Ichiroh; Nakazawa, Kimitaka

doi:10.1016/j.jelekin.2009.04.003

« Previous Next »Journal of Electromyography and Kinesiology
Volume 20, Issue 3 , Pages 406-412, June 2010

Enhanced stretch reflex excitability in the soleus muscle during passive standing posture in humans

Sachio Shimba
- Graduate School of Engineering, Shibaura Institute of Technology, 307 Fukasaku, Minuma, Saitama 337-8570, Japan
Noritaka Kawashima
- Department of Rehabilitation for Movement Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, 4-1 Namiki, Tokorozawa, Saitama 359-8555, Japan
- Lyndhurst Center, Toronto Rehabilitation Institute, 520 Sutherland Dr., Toronto, Ontario M4G 3V9, Canada
- Japanese Society for Promotion of Science, 1-8 Chiyoda, Tokyo 102-8472, Japan
- Corresponding author. Address: Department of Rehabilitation for Movement Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, 4-1 Namiki, Tokorozawa, Saitama 359-8555, Japan. Tel.: +81 42 995 3100; fax: +81 42 995 3132.
Yuji Ohta
- Faculty of Human Life and Environmental Science, Ochanomizu University, 2-1-1 Otsuka, Bunkyo, Tokyo 112-8610, Japan
Shin-Ichiroh Yamamoto
- Graduate School of Engineering, Shibaura Institute of Technology, 307 Fukasaku, Minuma, Saitama 337-8570, Japan
Kimitaka Nakazawa
- Department of Rehabilitation for Movement Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, 4-1 Namiki, Tokorozawa, Saitama 359-8555, Japan

Received 31 July 2008; received in revised form 10 February 2009; accepted 4 April 2009. published online 08 May 2009.

Abstract

The purpose of this study was to test whether the spinal reflex excitability of the soleus muscle is modulated as posture changes from a supine to a passive upright position. Eight healthy subjects (29.6±5.4 yrs) participated in this study. Stretch and H-reflex responses were elicited while the subjects maintained passive standing (ST) and supine (SP) postures. The passive standing posture was accomplished by using a gait orthosis to which a custom-made device was mounted to elicit stretch reflex in the soleus muscle. This orthosis makes it possible to elicit stretch and H-reflexes without background muscle activity in the soleus muscle. The results revealed that the H-reflex amplitude in the ST was smaller than that in the SP condition, which is in good agreement with previous reports. On the other hand, the stretch reflex was significantly larger in the ST than in the SP condition. Since the experimental conditions of both the stretch and H-reflex measurements were exactly the same, the results were attributed to differences in the underlying neural mechanisms of the two reflex systems: different sensitivity of the presynaptic inhibition onto the spinal motoneuron pool and/or a change in the muscle spindle sensitivity.