Co-activation of diaphragm and bicep in response to trans-spinal magnetic stimulation in healthy males

Abstract

Magnetic stimulation is a non-invasive approach to activate the neural tissue and induce the motor evoked potential. Diaphragm and bicep are innervating by motoneurons located within the mid-cervical spine cord; thus, the present study was designed to evaluate whether trans-spinal magnetic stimulation can co-activate the diaphragm and bicep in healthy male subjects (n=12) (KMUHIRB-F(I)-20210039). The two wings of the figure-of-eight magnetic coil (MCF-B65, inner diameter: 35 mm; out diameter: 75 mm) were placed on the dorsal vertebrae from the fifth cervical to the second thoracic vertebral column and its handle was vertical to the spine. The surface electromyogram of the bilateral diaphragm and bicep was recorded in response to trans-spinal magnetic stimulation with 20-100% maximum output of the stimulatory device. The results showed that trans-spinal magnetic stimulation can co-activate both muscles when the stimulatory intensity reached 60%. Notably, the intensity-response curve of motor evoked potential was significantly different between diaphragm and bicep. Specifically, the normalized response curve of the bicep was generally greater than that of the diaphragm, suggesting the excitability and responsiveness of bicep were greater than that of the diaphragm during trans-spinal magnetic stimulation. In addition, the motor evoked potential of the right diaphragm and bicep was greater than the left side during low stimulatory intensity, indicating there are anatomical and/or physiological differences between left and right muscles. In conclusion, trans-spinal magnetic stimulation with two coil wings along the vertebrae can co-activate the diaphragm and bicep. This trans-spinal magnetic stimulatory configuration can be considered as a feasible and efficient neuro-rehabilitative strategy to activate muscles innervating by the cervical spinal cord in subjects with impaired respiratory and forelimb motor function. The Ministry of Science and Technology (MOST 110-2636-B-110-001 & 111-2636-B-110-001). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.