The success of intramuscular stimulation relies heavily on a thorough physical examination by a competent practitioner, trained to recognize the physical signs of segmental changes according to segmental innervations of the spinal nerve. These segmental changes are influenced by descending pathways from higher centers of the CNS and/or ascending pathways from peripherally innervated areas. These changes are actual phenomena but are frequently unrecognized by imaging studies such as X-rays, CT scans and MRI. To find abnormal segmental changes, a physical examination with exact palpation is essential. Therefore, in this chapter, we introduce the segmental changes in view of a physical examination and target areas according to dermatomes of the spinal nerve from the cervical and lumbosacral regions.