We tested the acute effect of exercises targeted simultaneously at cortical and brainstem circuits on neural transmission through corticobulbar connections. Corticobulbar pathways represent a potential target for rehabilitation after spinal cord injury (SCI), which tends to spare brainstem circuits to a greater degree than cortical circuits. To explore this concept, able-bodied volunteers (n=20) underwent one session each of three exercises targeted at different nervous system components: treadmill walking (spinal locomotor circuits), isolated balance exercise (brainstem and other pathways), and multimodal balance plus skilled hand exercise (hand motor cortex and corticospinal tract). We found that short-interval soleus H-reflex facilitation increased after one session of balance and multimodal exercise by 13.2±4.0% and 8.3±4.7%, and slightly decreased by 1.9±4.4% after treadmill exercise (p=0.042 on ANOVA across exercise type). Increases in long-interval H-reflex facilitation were not significantly different between exercises. Both balance and multimodal exercise increased central motor conduction velocity by 4.3±2.6% and 4.5±2.8%, whereas velocity decreased by 4.3±2.7% after treadmill exercise (p=0.045 on ANOVA across exercise type). In conclusion, electrophysiological transmission between the motor cortex and spinal motor neurons in able-bodied subjects increased more following one session of balance exercise than treadmill exercise.
Keywords: Balance exercise; Corticospinal; H-reflex facilitation; Reticulospinal; Transcranial magnetic stimulation.
Published by Elsevier Ltd.