ABSTRACT

　The purpose of this study was to examine reproducibility of recruitment propertiesof the spinal reflexes evoked by a transcutaneous spinal cord stimulation （tSCS）between days. Twenty males（ 25.8 ± 3.4 years） participated in this study. Experimentswere conducted while the subjects were in the supine position. Recruitment curveswere obtained from the spinal reflexes evoked by tSCS in two consecutive days. Apaired-pulse stimulation with 50 ms inter-pulse interval was delivered to confirm thatresponses were caused by activation of the sensory fibers. Surface electromyography（EMG） of eight muscles in the lower-limbs（ i.e., foot, shank, and thigh muscles） wasrecorded. Peak-to-peak EMG amplitudes of the first response was calculated for each muscle when no response was observed in the second response. Threshold intensityof the responses was defined as the minimum stimulation intensity that producedthe responses, and maximal slope of the responses was determined by fitting sixorderpolynomial function to the recruitment curve. Inter-day reproducibility of therecruitment parameters was quantified using intraclass correlation coefficients（ ICC）.ICCs of threshold intensity for each muscle ranged between 0.487 and 0.874, and ICCsof maximal slope ranged between 0.474 and 0.964. These results suggest moderate tohigh reproducibility of the parameters of the recruitment curve of spinal reflexes inlower-limbs. Therefore, spinal reflexes evoked by tSCS could be useful in longitudinalneurophysiological studies.

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