title: Tibialis Anterior and Soleus Withdrawal Reflexes Elicited by Electrical Stimulation of the Sole of the Foot during Gait.
abstract: The aim of the present study was to investigate the modulation and functional importance of nociceptive withdrawal reflexes elicited from the sole of the foot and recorded from the soleus (SOL) and tibialis anterior (TA) muscles during gait. Cutaneous electrical stimulation delivered at four locations of the sole of the foot was used to elicit the withdrawal reflex. Reflexes were recorded from eight healthy subjects during treadmill walking. The reflexes were elicited at heel-contact, during foot-flat, at heel-off, and during mid-swing. The reflexes evoked in TA were largest when the arch of the foot was stimulated, and smallest following stimulation of the heel (significant difference during stance, p ≤ 0.002). The largest soleus responses were elicited when the arch of the foot was stimulated (significant difference compared with the fifth metatarsophalangeal joint, stimulation after heel-contact, p < 0.05). The TA reflex, expressed as a proportion of the electromyogram during unperturbed gait, was smallest during swing (p < 0.05, compared with stance) whereas the SOL reflex was maximal during swing (p < 0.05, compared with stance). The results suggest that the modulation of the reflex promotes an appropriate withdrawal while preserving balance and continuity of motion. These results may have applications in assisting gait of hemiplegics.
authors.affiliation: Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark.
authors.forename: Erika G
authors.initials: EG
authors.lastname: Spaich
authors.forename: Ole K
authors.initials: OK
authors.lastname: Andersen
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen