Effects of Shoe Type and Walking Speed on Knee Joint Loads / 医用生物力学

Objective To investigate the effects of shoes type (barefoot, ordinary running shoes, minimalist shoes) and walking speed (jogging, walking at normal speed) on biomechanical parameters of knee joint, so as to provide theoretical reference for scientific fitness. Methods Vicon three-dimensional （3D） motion capture system and Kistler 3D force plate were used to collect biomechanical parameters of lower limbs from 10 subjects during walking at different speed with different shoes. Two-way (2 walking conditions × 3 shoe conditions) repeated measures analysis of variance was used to statistically analyze each dependent variable. Results Compared with jogging, the lateral excursion of plantar center of pressure (COP) was greater, the moment arm in frontal plane, the adduction moment and peak loading rate of knee joint were smaller, but the angular impulse of knee joint in frontal plane was greater. Compared with ordinary running shoes, the stride length was decreased, the lateral excursion of COP was greater, and the moment arm of knee joint in frontal plane, the knee adduction moment, the peak load rate and the angular impulse of knee joint in frontal plane were smaller. Conclusions In order to reduce the angular impulse and peak loading rate of knee joint in frontal plane, it is recommended to jog with small strides for ordinary people with minimalist footwear.

Effects of Gait Retraining on Impact Forces, Lower Limb Biomechanics and Leg Stiffness / 医用生物力学

Objective By establishing the intervention mode of 12-week gait retraining (GR) (with the specific aim of changing the habitual running gait), to determine the changes of vertical ground reaction force (vGRF), kinematics and dynamics of hip, knee, ankle joints, as well as stiffness of lower limbs in running before and after GR, and to explore the influence of running posture transformation on impact force and lower limb biomechanics. Methods Vicon motion capture system and Kistler 3D force measurement platform were used to collect the GRF and marker track of 30 runners (15 in experimental group and 15 in control group) before and after GR with the minimalist shoes at a speed of 12 km/h±5%. Results A total of 17 subjects (9 in experimental group and 8 in control group) completed the GR. After GR, the maximum loading rate of both groups decreased significantly, and the maximum loading rate of experimental group was lower than that of control group. The foot strike angle in experimental group decreased significantly after GR, and the plantarflexion angle and hip joint angular extension velocity increased in both groups. The force moment of ankle joint increased in experimental group, and the stiffness of lower limbs was significantly improved in both groups. Conclusions A 12-week GR exercise intervention model was successfully established, with 78% conversion rate (from rearfoot strike to forefoot strike). GR can effectively avoid the peak of impact force, reduce the maximum loading rate, increase the lower limb stiffness, and thus reduce or even avoid the risk of running injury caused by impact force and may provide a possibility for the improvement of running economy.