METHODS: The experimental design was a prospective physiologic evaluation of the effects of SM on corticospinal excitability in asymptomatic subjects. The TMS-induced MEPs were recorded from relaxed lumbar erector spinae muscles of 72 asymptomatic subjects. The MEP amplitudes were evaluated pre-SM and post-SM or conditions involving prethrust positioning and joint loading or control.
RESULTS: There was a transient increase in MEP amplitudes from the paraspinal muscles as a consequence of lumbar SM (F([6,414]) = 8.49; P < .05) without concomitant changes after prethrust positioning and joint loading or in control subjects (P > .05). These data findings were substantiated by a significant condition x time interaction term (F([12,414]) = 2.28; P < .05).
CONCLUSIONS: These data suggest that there is a postsynaptic facilitation of alpha motoneurons and/or corticomotoneurons innervating paraspinal muscles as a consequence of SM. It appears that SM may offer unique sensory input to the excitability of the motor system as compared to prethrust positioning and joint loading and control conditions.
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