It has been shown in side impact automobile accidents that the shoulder is the point of first contact with the intruding door, causing large forces to be carried by the shoulder complex and, upon failure, into the thorax of the occupant. Shoulder kinematics and the distribution of load through the shoulder girdle are well documented for every day functions;​ however, the response of the shoulder to impact and the transmission of load to the thorax under high-energy impact are not well understood. The mechanical response, or stiffness properties, of the shoulder that would be helpful in future dummy development is also not known. The shoulder response under the oblique loading that occurs when the intruding door does not strike in a purely lateral manner is unknown. The response of the shoulder to impact and the protective relationship between the shoulder girdle and the thorax is critical to understanding human response to lateral impact and to developing countermeasures to prevent and mitigate thoracic, as well as shoulder, trauma. The purpose of this study was to define injury criteria for the shoulder, define the stiffness of the shoulder in response to both lateral and oblique loading, and investigate the protective relationship between the shoulder girdle and the thorax. This study was conducted in two separate phases. Phase I of the research was comprised of 24 lateral shoulder impacts. Phase 11 included 14 lateral and oblique shoulder impacts. Of the 14 tests, four of them were conducted lateral to the shoulder along the subject's y-axis, four of them were conducted 15° anterior to this axis, and six were conducted 30° anterior to the subject's y-axis. All of the testing utilized a pneumatic ram to impact the shoulders of post-mortem human subjects (PMHSs) at the level of the glenohumeral joint. The first thoracic vertebrae and both shoulders of the subject were instrumented with tri-axial linear accelerometers on the sternum, clavicle, acromion process, and inferior angle of the scapula. The impacting mass was instrumented with an accelerometer and displacement transducer. In addition to this instrumentation, the tests were documented by high-speed digital imagery. Radiographs (x-rays), magnetic resonance images (MRls), and autopsies were used to document injury to the subjects. The results from the two phases of testing revealed differences between the stiffness of the shoulder when loaded laterally to that when it is loaded obliquely. The shoulder was found to deflect more medially when loaded obliquely then when it is loaded laterally. This can be attributed to the ability of the scapula to slide posteriorly around the thoracic cage. The ability of the shoulder to displace medially while simultaneously deflecting posteriorly in oblique impact is important to replicate in the ATDs because it results in the load being transmitted to the upper thoracic cage.