Experimental study on the half-squat parachute landing for driving and validating the inverse dynamic simulation / 医用生物力学

Objective To provide data for establishing, driving and validating the inverse dynamics model of AnyBody Modeling System, the simulated half squat parachute landing experiment was designed and relevant data were collected. Method The subject was required to jump from a 0.32 m high platform to simulate the half squat parachute landing. The kinematic parameter of lower extremity joint, the ground reaction force and the surface electromyogram (SEMG) of four main muscles in the lower extremity joint were measured simultaneously. Results The angle changes of hip, knee and ankle along with time in three anatomical planes, the ground reaction force of right foot and the trajectory of the center of pressure were collected within 1 second just before and after the subject landing. These data would be used to drive the muscleskeletal model, while the data for measuring electromyogram activity would be used to validate the model. Conclusions The experiment meets the requirement of muscleskeletal model analysis, which can be used for further study of half squat parachute landing.

Finite element study on knee injuries in the parachute landing / 医用生物力学

Objective To numerically simulate the half squat parachute landing and analyze the mechanism of knee injuries with the finite element method based on the data of the simulated parachute landing experiment. Method The half squat parachuting experiment was performed by 16 healthy volunteers. The heights of simulated landing were 0.32 m, 0.52 m and 0.72 m respectively. A three dimensional finite element model of human knee joint was developed based on magnetic resonance images. The kinematical data of the knee and the data of the reaction force obtained by experiments were used to make a numerical simulation of the parachute landing process. Results The stress level of the knee increased with the increase of the height. The lateral meniscus and cartilage suffered greater loads than the medial ones. Obvious stress concentrations occurred in the anterior cruciate ligament and the medial collateral ligament when the knee flexion degree reached the peak value. Conclusions The severe impact in parachute landing is the direct cause of injuries in parachute landing. The lateral cartilage and meniscus are more likely to be injured, and the anterior cruciate ligament and the medial collateral ligament are easier to tear when the knee flexion degree reaches the peak value.

Effects of ankle stabilizers on electromyographic activities of lower extremity muscles during simulated half-squat parachute landing / 医用生物力学

Objective To study effects of ankle stabilizer on electromyographic activities of lower extremity muscles during the simulated half squat parachute landing and its gender differences. Method Eight male and eight female healthy adults were required to jump from a platform of 0.72 m high to simulate half squat parachute landing. The experiment was divided into 3 groups: the barefoot one as control group, the group wearing tapes and braces respectively. The electromyogram (EMG) of each subject’s tibial anterior, lateral gastrocnemius, biceps femoralis and rectus femoralis was measured. Two way ANOVA was used to analyze and evaluate the effect of the stabilizers and genders on EMG variables. Results The use of brace significantly increased the pre landing EMG amplitude of the tibialis anterior for male (Control: 266 μV; Tape: 368 μV; Brace: 552 μV). The stabilizers had no significant effects on the other EMG parameters. Conclusions Semi rigid ankle braces are capable of arousing more active EMG of male’s ankle flexor during half squat parachute landing, but female does not share this predominance. Ankle stabilizers have no significant effects on EMG activities for knee joints.