Spatial factors and muscle spindle input influence the generation of  neuromuscular responses to stimulation of the human foot.
Removal of the mechanical pressure gradient on the soles leads to physiological adaptations that ultimately result in neuromotor degradation during spaceflight. We propose that mechanical stimulation of the soles serves to partially restore the afference associated with bipedal loading and assists in attenuating the negative neuromotor consequences of spaceflight. A dynamic foot stimulus device was used to stimulate the soles in a variety of conditions with different stimulation locations, stimulation patterns and muscle spindle input. Surface electromyography revealed the lateral side of the sole elicited the greatest neuromuscular response in ankle musculature, followed by the medial side, then the heel. These responses were modified by preceding stimulation. Neuromuscular responses were also influenced by the level of muscle spindle input. 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 spaceflight.
Layne
Charles S
CS
Laboratory of Integrated Physiology, Department of Health and Human Performance, University of Houston, TX 77024-6015, USA. clayne2@uh.edu
Forth
Katharine E
KE
Abercromby
Andrew F J
AF
D000293:Adolescent; D000328:Adult; D000842:Ankle / Q000502:physiology; D004576:Electromyography; D005081:Exercise Therapy; D005260:Female; D005528:Foot / Q000294:innervation / Q000502:physiology*; D007839:Functional Laterality; D006365:Heel; D006801:Humans; D008297:Male; D009470:Muscle Spindles / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010812:Physical Stimulation; D001405:Reflex, Babinski; D013026:Space Flight; D014732:Vibration; D014893:Weightlessness / Q000009:adverse effects; D018544:Weightlessness Countermeasures