title: The relationship between dynamic balancing ability and posture-related modulation of the soleus H-reflex.
abstract: Soleus H-reflex reveals down modulation with increased postural difficulty. Role of this posture-related reflex modulation is thought to shift movement control toward higher motor centers in order to facilitate more precise postural control. Present study hypothesized that the ability to modulate H-reflex is related to one's ability to dynamically balance while in an unstable posture. This study examined the relationship between dynamic balancing ability and soleus H-reflex posture-related modulation. Thirty healthy adults participated. The soleus maximal H-reflex (Hmax), motor response (Mmax), and background EMG activity (bEMG) were obtained during three postural conditions: prone, open-legged standing, and closed-legged standing. Hmax/Mmax ratios were normalized via the corresponding bEMG in order to remove the effects of background muscle activity from the obtained H-reflex. Reflex modulation was calculated as the ratio of the normalized Hmax/Mmax ratios in one postural condition to another posture in a more difficult condition. Dynamic balancing ability was assessed by testing stability while standing on a wobble board. A significant negative correlation was observed between balancing scores and reflex modulation from open-legged standing to closed-legged standing. This suggests that the ability to modulate monosynaptic stretch reflex excitability in response to a changing posture is a significant factor for dynamic balancing.
authors.affiliation: Department of Rehabilitation, Kobe Rehabilitation Hospital, Japan; Department of Rehabilitation Medicine, The Hyogo College of Medicine, Japan. Electronic address: yuyakedomo@yahoo.co.jp.
authors.forename: Yu
authors.initials: Y
authors.lastname: Kawaishi
authors.affiliation: Department of Rehabilitation Medicine, The Hyogo College of Medicine, Japan.
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Domen
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology; D016684:Prone Position / Q000502:physiology; D055815:Young Adult
keywords: Balancing; H-reflex; Modulation; Posture