 At this point, subjects will be taken to a quiet room located within the Department of Physical Therapy. This room is used as a lab and data collection room and has a physical therapy treatment table. The subject will be asked to lie prone on the table and an electrocardiographic recording sensory will be placed upon each wrist two total. This sensory will feed data regarding heart rate to a laptop computer that will be collected using the Biocomm HRV Live! Heart Rate Variability HRV Data Acquisition program. Once the strength and stability of the signal is verified, the subject will be instructed to rest quietly for five minutes in order to gather baseline heart rate data. Following this five-minute timeframe, the subject will receive one of three interventions based upon the previously mentioned randomization process. The three interventions utilized in the study will be a posterior to anterior spinal manipulation delivered to T4-5 spinal segment, posterior to anterior spinal mobilization applied to the T4-5 spinal segment for 30 seconds, or sham therapeutic ultrasound applied to the T4-5 spinal region bilaterally for 30 seconds the ultrasound machines will not be turned on. Between each of these interventions, subjects will be instructed to rest quietly for five minutes in order to stabilize the bodys cardiovagal responses. Following completion of these three interventions, subjects will allowed to ask additional questions and will be given the number of the principal investigator and the IRB office to contact if they have questions or concerns in the future. 