Modeling and analysis of firefighter musculoskeletal biomechanics for lower-extremity exoskeletons

Firefighters face arduous tasks and extreme physical demands as part of their regular work.

This paper analyzes biomechanical data from four firefighting activities to identify critical areas requiring support and evaluates the effectiveness of integrating spring-based passive assistance and active assistance during these selected activities. Crucial areas demanding support were identified by analyzing joint torque profiles, joint reaction forces, and muscle group activation levels during the chosen firefighting activities. The impact of incorporating spring-based passive assistance and active assistance was examined through muscle activation data generated from full-body subject-specific musculoskeletal simulations and motion capture.

The simulation results were rigorously assessed for potential lower-body exoskeleton solutions through statistical analysis employing the Wilcoxon signed-rank test. Passive hip assistance proved effective for rescue operations (body drag) based on the results where hip flexor muscles demonstrated a large decrease in muscle activity (P<0.05 and d>0.8). The active hip assistance demonstrated efficacy across all four firefighting activities, showcasing a decrease in average hip muscle activation levels (P<0.05 and d>0 for all activities). Additionally, employing simultaneous active assistance at the hip, knee, and ankle joints resulted in a substantial reduction in the overall leg muscle profile, with a significant impact during stair climb (P<0.05 and d>0.8) and a moderate effect during equipment carry, hose drag, and rescue (body drag).