Lower extremity kinematic and kinetic characteristicsof firefighters' rescue for different tasks

To investigate the lower-extremity kinematic and kinetic features of firefighters under different rescue loads and provide evidence for injury prevention in firefighting training and field rescue.

Eleven healthy male firefighters from Guilin Fire and Rescue Department completed four experimental protocols: baseline wearing 12.5 kg firefighting protective equipment (FPE), FPE plus 15 kg gas canister (FPE+GC), FPE plus 30 kg fire ladder (FPE+FL), and FPE plus 60 kg rescue dummy (FPE+D). The Qualisys infrared motion capture system and AMTI force platform were adopted to acquire kinematic and kinetic data.

Relative to the FPE condition, FPE + FL and FPE + D significantly shortened step length, support duration and stride speed (p < 0.05); these indicators were also significantly lower than FPE + GC, and FPE + D further decreased support time and stride speed (p < 0.05). Compared with FPE, FPE + FL and FPE + D induced significantly larger peak hip extension and ankle dorsiflexion angles as well as elevated hip/knee joint moment, power, joint work and peak vertical ground reaction force (vGRF) (p < 0.05), whereas only ankle dorsiflexion angle significantly increased in FPE + GC (p < 0.05). All three loaded groups displayed elevated total hip work and higher hip work proportion accompanied by reduced ankle work contribution (p < 0.05). FPE + D produced remarkably greater joint work metrics than FPE and FPE + GC (p < 0.05); meanwhile, FPE + FL and FPE + D had higher hip extension moment, ankle dorsiflexion moment, knee work and peak vGRF than FPE + GC (p < 0.05).\ CONCLUSION: Firefighters shorten step length and rely on compensatory hip and knee movements to accommodate increasing external load. The ultra-heavy dummy load in FPE + D substantially increases hip and knee injury risk; targeted hip-knee strength training is recommended to reduce injury occurrence during heavy-load rescue operations.