The thorax is frequently involved in side impact accidents; in such accidents, injuries to the thorax are related to the intrusion. The position of the impacted side arm can affect the occuring of thoracic injuries in side impact. This study describes the results of 15 side impact thoracic tests performed on 8 cadavers; most of these tests are conducted with arm involvement (the upper arm is places along the thorax and the impact is transmitted to the thorax through the arm). The results of these tests are compared to the results of 6 tests previously published, conducted without arm involvement (the impact was applied directly to the thorax). From these results, it appears that the arm offers a limited protection when it is placed along the thorax, by distributing impact forces on the chest, and that the BLUR criterion is not well correlated with the thoracic injuries severity.