Biomechanical characterization of firefighters running under different rescue tasks

The biomechanical characteristics of runs in firefighters with different rescue tasks are unclear. This study aimed to explore the biomechanical characteristics of firefighters running in different rescue tasks and provide theoretical and practical references for firefighter training and occupational injury prevention. Eighteen professional healthy male firefighters were randomly selected as participants and tested running on different rescue tasks: wearing firefighting protective clothing (FPC), FPC+carrying a gas can (20 kg, FPC+ C), and FPC+carrying a mannequin (60 kg, FPC+M). Eight Qualisys infrared cameras and an AMTI 3D force measurement platform were used for the participant's acquisition of lower limb kinematic/kinetic data. The results showed that gait velocity and stride length of the FPC+GC and FPC+ M rescue tasks were significantly decreased compared to the FPC rescue task, while the support time was significantly increased. Compared to the FPC rescue task, the FPC+GC rescue task showed significant decreases in vertical ground reaction force (vGRF), minimum ankle dorsiflexion angle, and the maximum ankle plantarflexion power. In contrast, the FPC+M rescue task demonstrated significant increases in ankle range of motion, maximum hip extension angle, minimum knee flexion angle, maximum ankle dorsiflexion angle, maximum hip extension moment, maximum knee flexion moment, maximum hip flexion power, and hip and knee stiffness while exhibiting significant decreases in minimum ankle dorsiflexion angle. Compared to the FPC+ GC rescue task, the FPC+M rescue task exhibited significant increases in the maximum hip extension angle, minimum knee flexion angle, maximum ankle dorsiflexion angle, maximum hip flexion moment, maximum hip extension moment, maximum knee flexion moment, maximum ankle plantarflexion moment, maximum hip flexion power, maximum ankle dorsiflexion power, hip stiffness, and vGRF. Conversely, it showed significant decreases in the maximum knee flexion power. In conclusion, compared to the FPC rescue task, the FPC+GC and FPC+M rescue tasks altered the firefighter's gait performance, as evidenced by decreased gait velocity and stride length and increased support time. FPC+M rescue task would increase firefighter's risk of hip and knee injuries. Therefore, we suggest firefighters increase their strength training of the trunk, hip, and knee joint muscles as part of their daily training programs under large weight load status (60 kg and above) to reduce injury risk during rescue tasks.