title: Arm sway holds sway: locomotor-like modulation of leg reflexes when arms swing in alternation.
abstract: It has been argued that arm movements are important during human gait because they affect leg activity due to neural coupling between arms and legs. Consequently, one would expect that locomotor-like alternating arm swing is more effective than in-phase swing in affecting the legs' motor output. Other alternating movements such as trunk rotation associated to arm swing could also affect leg reflexes. Here, we assessed how locomotor-like movement patterns would affect soleus H-reflexes in 13 subjects performing arm swing in the sagittal plane (ipsilateral, contralateral and bilateral in-phase versus locomotor-like anti-phase arm movements) and trunk rotation with the legs stationary, and leg stepping with the arms stationary. Findings revealed that soleus H-reflexes were suppressed for all arm, trunk or leg movements. However, a marked reflex modulation occurred during locomotor-like anti-phase arm swing, as was also the case during leg stepping, and this modulation flattened out during in-phase arm swing. This modulation had a peculiar bell shape and showed maximum suppression at a moment where the heel-strike would occur during a normal walking cycle. Furthermore, this modulation was independent from electromyographic activity, suggesting a spinal processing at premotoneuronal level. Therefore, trunk movement can affect legs' output, and a special neural coupling occurs between arms and legs when arms move in alternation. This may have implications for gait rehabilitation.
authors.affiliation: Research Center for Movement Control and Neuroplasticity, Department of Kinesiology, Faculty of Kinesiology and Rehabilitation Sciences, K.U. Leuven, Heverlee, Belgium. Electronic address: firas.massaad@gmail.com.
authors.forename: F
authors.initials: F
authors.lastname: Massaad
authors.affiliation: Research Center for Movement Control and Neuroplasticity, Department of Kinesiology, Faculty of Kinesiology and Rehabilitation Sciences, K.U. Leuven, Heverlee, Belgium.
authors.forename: O
authors.initials: O
authors.lastname: Levin
authors.affiliation: Research Center for Movement Control and Neuroplasticity, Department of Kinesiology, Faculty of Kinesiology and Rehabilitation Sciences, K.U. Leuven, Heverlee, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Meyns
authors.affiliation: Research Center for Movement Control and Neuroplasticity, Department of Kinesiology, Faculty of Kinesiology and Rehabilitation Sciences, K.U. Leuven, Heverlee, Belgium.
authors.forename: D
authors.initials: D
authors.lastname: Drijkoningen
authors.affiliation: Research Center for Movement Control and Neuroplasticity, Department of Kinesiology, Faculty of Kinesiology and Rehabilitation Sciences, K.U. Leuven, Heverlee, Belgium.
authors.forename: S P
authors.initials: SP
authors.lastname: Swinnen
authors.affiliation: Research Center for Movement Control and Neuroplasticity, Department of Kinesiology, Faculty of Kinesiology and Rehabilitation Sciences, K.U. Leuven, Heverlee, Belgium; Department of Research, Development and Education, Sint Maartenskliniek, Nijmegen, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Duysens
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology*; D001696:Biomechanical Phenomena; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D007866:Leg / Q000502:physiology*; D008124:Locomotion / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D060726:Torso / Q000502:physiology
keywords: CPG; EMG; H-reflex; M-max; RMS; arm movement; central pattern generators; central-pattern-generator; electromyography; locomotion; maximal M-wave; root mean square