Abstract
Modifications in load-related sensory input during unloaded walking can lead to recalibration of the body schema and result in aftereffects. The main objective of this study was to identify the adaptive changes in gait and body-weight perception produced by unloaded walking. Gait performance during treadmill walking was assessed in 12 young participants before and after 30 min of unloaded walking (38% body weight) by measuring lower limb kinematics, temporal gait measures, and electromyography (EMG). A customized weight-perception scale was used to assess perception of body weight. Participants perceived their body weight to be significantly heavier than normal after unloading while walking. Angular displacement about ankle and knee was significantly reduced immediately after unloaded walking, while temporal gait parameters remained unchanged. The EMG activity in some muscles was significantly reduced after unloading. These findings indicate that walking at reduced body weight results in alterations in segmental kinematics, neuromuscular activity, and perception of body weight, which are the aftereffects of motor adaptation to altered load-related afferent information produced by unloading. Understanding the adaptive responses of gait to unloading and the time course of the aftereffects will be useful for practitioners who use body-weight unloading for rehabilitation.
Highlights
The sensorimotor system is comprised of sensory systems, motor systems, and the central integration processes that help in producing and controlling movements
Alterations in kinematics and neuromuscular activities observed during unloaded walking are a result of the adaptation of the neuromuscular system to the reduction in ground reaction forces, shear forces, foot sole pressure, and joint loads associated with unloading
These changes are caused due to somatosensory-mediated central changes in the body schema produced by new relationships between sensory and motor elements that are characteristic to an unloaded environment
Summary
The sensorimotor system is comprised of sensory systems, motor systems, and the central integration processes that help in producing and controlling movements. The vestibular, proprioceptive, and visual systems provide sensory information from the external environment as well as that related to body position and movement. The sensory inputs from these systems are integrated in the central nervous system (CNS) following which appropriate motor commands are generated and sent through the descending pathways to the various body segments. Any changes in the sensory information either due to changes in the environmental condition or body condition will affect movement control. The process that enables us to modify and maintain accurate movements as sensory condition changes is called motor adaptation [1]. Several studies have investigated motor adaptation using a variety of experimental paradigms
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