Muscle Reflexes as Modulated Preparatory Neuromuscular Activation Levels / 31-40
Charles S. Layne
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Abstract--Mechanical stimulation of the soles can result in lower limb muscle contraction. This suggests that controlled stimulation to the soles may be used to "drive" muscle activation that can assist in maintaining the functional integrity of lower limb muscles during extended-duration space flight. A Dynamic Foot Stimulus device, (DFS) composed of multiple solenoids, was used to stimulate the right sole of seated subjects. To modify muscle spindle input, in advance of the stimulus, ankle angle was varied across stimulation conditions while other another condition involved vibration of the Achilles tendon. Surface electromyography (EMG) revealed that stimulation led to significant neuromuscular responses in the ankle musculature that were influenced by the amount of muscle spindle input related to ankle muscle length and tendon vibration. These results provide important information that can be used to guide the development of a "passive" countermeasure that relies on sole stimulation and can supplement existing exercise protocols during space flight.