Athletes competing in the unarmed combat sport of mixed martial arts (MMA) are at an increased risk for long-term neurological consequences due to repetitive head trauma. Mass differentials as well as reported differences in fight styles between Lightweight and Heavyweight fighters in MMA may affect head impact kinematics creating different levels of head injury risk. Factors that influence the risk for head injury include the frequency, magnitude and interval of head impacts. The purpose of this study was to compare differences in frequency, frequency distribution of impact magnitudes, and time interval between head impacts per match between Lightweight and Heavyweight fighters in the Ultimate Fighting Championship (UFC).

Head impacts of 60 fighters were documented from 15 Lightweight and 15 Heavyweight MMA fight videos. Impact type, frequency, and interval were recorded for each fighter, followed by the reconstruction of 345 exemplar impacts in the laboratory using a Hybrid III headform and finite element modeling to determine impact magnitudes. Next, head impacts (punches, kicks, knees and elbows) from fight videos were visually estimated to determine their corresponding magnitude range and establish the frequency distribution of impact magnitudes. The study revealed no significant differences in overall impact frequency and interval between Lightweight and Heavyweight fighters. The frequency distribution of different impact magnitudes was significantly different, with Lightweights sustaining significantly more Very Low, and High magnitude impacts. Overall, both Lightweight and Heavyweight MMA fighters sustain similar impact characteristics as other high-risk athletes including professional boxers and football players. Understanding the different factors that create brain trauma allows for the monitoring, identification, and protection of higher-risk athletes within these two weight classes.