Beyond the Hit: Muscle and Vascular Tissue Responses to Contact Exposure in Collision Sports-A Narrative Review

Contact events in rugby codes such as tackling, running into contact, scrums, rucks, and contact with the playing surface may expose athletes to muscle damage known as impact-induced muscle damage. These repetitive impacts to muscle tissue have the potential to diminish muscle force production and delay recovery following contact-focused training and match-play. Repetitive exposure to contacts may also affect the surrounding vascular and neuronal tissues, an area that has received little attention in the collision sports. Depending on the severity and duration of tissue damage, repetitive contact exposure without sufficient recovery or noticeable adaptation may predispose collision sport athletes to impaired performance and long-term health complications. The aim of this narrative review is to provide a conceptual framework for understanding the physiological implications of contact exposure in collision sports. We examine the current understanding of impact-induced muscle damage (IIMD), how it differs from exercise-induced muscle damage (EIMD), and its relationship with contact exposure in collision sports. Drawing on both experimental animal models of contusion injury and limited human observational research, we explore the effects of repeated contact exposure on the microvasculature and its implications for both athletic performance and player welfare. To account for all tissues that may be affected by impacts, including muscle, nerve, vascular, connective tissue, skin, other organs and bones, we recommend impact-induced tissue damage (IITD) as the preferred descriptor rather than IIMD. Finally, we discuss the concept of contact adaptation and provide recommendations for future research on IITD in collision sports.