Reflexive muscular bracing of the lower extremities can play a significant role in occupant kinematics and kinetics. It is known that the muscles of the legs can generate substantial resisting forces that could be used to help the occupant ride down the crash. The consequences of muscular bracing on injury are investigated with numerical simulations and laboratory studies. The tests suggest that muscular bracing acts to increase the peak axial load in the tibia and the impulse absorbed by the leg; however, these values were not injurious when intrusion was not present. Numerical simulation of intrusion suggested that loading of the tensed leg could exceed the published injury threshold.