Shoulder-to-helmet (STH) impacts have been shown to cause approximately twenty percent of concussions in football, yet little research has investigated shoulder pad design and STH impacts. While shoulder pads are designed to protect the player wearing them, they have the potential to better protect the struck player in STH collisions. This study aimed to characterize STH impacts and identify the effect of shoulder pad stiffness on the struck head kinematics. Additional padding was added to a shoulder pad as means to reduce the overall stiffness of the system, and an unmodified shoulder pad acted as the control. Participants performed a series of impact tests with two shoulder pad variations to identify if additional padding in the shoulder pads could reduce head kinematics. Participants struck a helmeted Hybrid III dummy with a National Operating Committee on Standards for Athletic Equipment (NOCSAE) on the side, replicating a lateral STH impact. Linear and rotational kinematics of the struck head were recorded for each impact, and impact speed was derived from high-speed video. Peak kinematics were compared between shoulder pad configurations to identify differences in pad performance. Impact response corridors were developed from this study that could be used to inform future controlled laboratory test setups that replicate STH impacts. A controlled test setup would allow for future testing at higher impacts speeds to evaluate concussive level impacts. Overall, this study aimed to identify if shoulder pad design can affect the struck head kinematics in STH impacts, which would open a new avenue of player safety research and development. / Master of Science / Shoulder-to-helmet (STH) impacts have been shown to cause approximately twenty percent of concussions in football, yet little research has investigated shoulder pad design and STH impacts. While shoulder pads are designed to protect the player wearing them, they have the potential to better protect the struck player in STH collisions. This study aimed to characterize STH impacts and identify the effect of shoulder pad stiffness on the struck head kinematics. Participants performed a series of impact tests with two shoulder pad variations to identify if additional padding in the shoulder pads could reduce head kinematics. Participants struck the side of a crash test dummy head with their shoulder to replicate a STH impact. Linear and rotational kinematics were recorded for each impact, and impact speed was derived from high-speed video. Values that are used to quantify head injury were compared between shoulder pad configurations to identify differences in pad performance. This study defined impact response corridors that could be used to inform future controlled lab test setups that replicate STH impacts. A controlled test setup would allow for future testing at higher impacts speeds to evaluate concussive level impacts. Overall, this study aimed to identify if shoulder pad design can affect the struck head kinematics in STH impacts, which would open a new avenue of player safety research and development.