title: Velocity-dependent suppression of the soleus H-reflex during robot-assisted passive stepping.
abstract: The amplitude of the Hoffmann (H)-reflex in the soleus (Sol) muscle is known to be suppressed during passive stepping compared with during passive standing. The reduction of the H-reflex is not due to load-related afferent inputs, but rather to movement-related afferent inputs from the lower limbs. To elucidate the underlying neural mechanisms of this inhibition, we investigated the effects of the stepping velocity on the Sol H-reflex during robot-assisted passive stepping in 11 healthy subjects. The Sol H-reflexes were recorded during passive standing and stepping at five stepping velocities (stride frequencies: 14, 21, 28, 35, and 42 min(-1)) in the air. The Sol H-reflexes were significantly inhibited during passive stepping as compared with during passive standing, and reduced in size as the stepping velocity increased. These results indicate that the extent of H-reflex suppression increases with increasing movement-related afferent inputs from the lower limbs during passive stepping. The velocity dependence suggests that the Ia afferent inputs from lower-limb muscles around the hip and knee joints are most probably related to this inhibition.
authors.affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan. Electronic address: yohei.masugi@gmail.com.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Masugi
authors.affiliation: Division of Functional Control Systems, Graduate School of Engineering and Science, Shibaura Institute of Technology, 307, Fukasaku, Minuma-ku, Saitama-shi, Saitama 337-8570, Japan; Department of Motor Dysfunction, Research Institute of National Rehabilitation Center for the Disabled, 4-1 Namiki, Tokorozawa-shi, Saitama 359-8555, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Kitamura
authors.affiliation: Faculty of Health and Sports Science, Doshisha University, 1-3 Tatara Miyakodani, Kyotanabe-shi, Kyoto 610-0394, Japan.
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Kamibayashi
authors.affiliation: Faculty of Sport Sciences, Graduate School of Sport Sciences, Waseda University, 2-579-15, Mikajima, Tokorozawa-shi, Saitama 359-1192, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ogawa
authors.affiliation: Department of Motor Dysfunction, Research Institute of National Rehabilitation Center for the Disabled, 4-1 Namiki, Tokorozawa-shi, Saitama 359-8555, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Ogata
authors.affiliation: Department of Motor Dysfunction, Research Institute of National Rehabilitation Center for the Disabled, 4-1 Namiki, Tokorozawa-shi, Saitama 359-8555, Japan.
authors.forename: Noritaka
authors.initials: N
authors.lastname: Kawashima
authors.affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan.
authors.forename: Kimitaka
authors.initials: K
authors.lastname: Nakazawa
mesh_terms: D000328:Adult; D006181:H-Reflex; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D007866:Leg / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture / Q000502:physiology; D012371:Robotics; D016138:Walking / Q000502:physiology*
keywords: Afferent input; Hoffmann reflex; Locomotion; Passive stepping; Velocity