The second point seems intuitive but there is a surprising lack of evidence showing that the increase in muscle size contributes to an increase in voluntary strength. If individuals increased both muscle size and strength, the conclusion is often that muscle growth played a role.
Your spinal cord is protected by the vertebral column (also known as the spinal column or backbone). The human spinal column is made up of 33 bones - 7 vertebrae in the cervical region, 12 in the thoracic region, 5 in the lumbar region, 5 in the sacral region and 4 in the coccygeal region.
