| Purpose:In recent years,urban cross-country running has gradually become popular and well known among the public,but running can cause some common sports injuries,including knee joint injuries,which are particularly common.The most common occurrence is Patellofemoral Pain(PFP)in the knee joint.Without early prevention,it may eventually develop into patellofemoral arthritis that is difficult to treat.More and more scholars have found that factors such as changing the way of landing during running,adjusting posture,selecting a running environment,and improving sports equipment can effectively reduce joint injury.The purpose of this study was to compare the effects of different slopes and angles on patellofemoral joint force,patellofemoral joint stress,and related parameters of lower limb kinematics and dynamics in healthy runners,in order to provide data basis for preventing knee and patellofemoral joint injury.Methods:Sixteen healthy,athletic boys were recruited to participate in the study.Using a three-dimensional dynamometer and Vicon analysis,runners were running at a speed of 2.78m/s at 0 °,up slope 3 °,6 °,9 °,and down slope 3 °,6 °,and 9 ° to sample three-dimensional running mechanics.Using a skeletal muscle model,biomechanical parameter data such as patellofemoral joint stress,patellofemoral joint force under peak patellofemoral joint stress,torso inclination angle,knee joint flexion angle,knee joint torque,and ground reaction force were obtained.A two-factor repeated measurement analysis of variance was used to analyze the relationship between different parameters under 2 slopes and 4 angles.Results:Slope and angle have significant interactions with the following indicators(p<0.001).(1)Patellofemoral Joint Stress(PFJS): Under the same slope,the patellofemoral joint stress has a significant difference(p<0.001).As the angle increases,the overall trend of increase is upward.The patellofemoral joint stress during downhill is always greater than the patellofemoral joint stress during upward slope at the same angle(p<0.001).The patellofemoral joint stress during the uphill process presents a U-shaped trend as the angle increases.The patellofemoral joint stress reached the minimum value at 3 ° uphill(p<0.001)and the maximum value at 9 ° downhill(p<0.001).(2)Patellofemoral Joint Force(PFJF): Under the same slope,there is a significant difference in patellofemoral joint force(p<0.001).The patellofemoral joint force during the downhill process is always greater than the patellofemoral joint force during the same angle uphill process.The patellofemoral joint force during the uphill process presents a U-shaped trend as the angle increases,and the patellofemoral joint force reaches the minimum value at 6 ° uphill(P=0.001),and reaches the maximum patellofemoral joint force at 9 ° downhill(p<0.001).(3)Trunk anteversion angle at peak stress of patellofemoral joint: Under the same slope,there are significant differences in trunk anteversion angles under four different angles(p<0.001).When going uphill,the torso forward tilt angle gradually increases as the angle increases.At the same angle,there is a significant difference in torso forward inclination between the two different slopes(p<0.001),and it is the torso forward inclination angle that is always greater on the uphill than on the downhill.Compared to 0 °,they experienced the maximum torso anteversion angle at 9 ° uphill(p=0.019)and the minimum torso anteversion angle at 9 ° downhill(p<0.001).(4)Knee flexion angle at peak patellofemoral joint stress: Under the same slope,there is a significant difference in knee flexion angle at peak patellofemoral joint stress(p<0.001).At the same angle,when climbing up,there is a greater knee flexion angle than when climbing down(p<0.001).At the same slope,the knee flexion angle increases as the angle increases.(5)Hip flexion angle at peak patellofemoral joint stress: Under the same slope,there is a significant difference in hip flexion angle at peak patellofemoral joint stress(p<0.001).At the same angle,there is a greater hip joint flexion angle when going uphill than when going downhill(p<0.001).During ascent,the hip joint flexion angle increases as the angle increases compared to 0 °,and during descent,the hip joint flexion angle decreases as the angle increases compared to 0 °.(6)Knee joint torque at peak patellofemoral joint stress: Under the same slope,there is a significant difference in knee joint torque at peak patellofemoral joint stress(p<0.001).The knee joint torque during downhill is always greater than the knee joint torque during uphill.During the uphill process,the knee joint torque gradually changes from extension torque to flexion torque(p<0.001).(7)Vertical ground reaction force at peak stress of patellofemoral joint: Under the same slope,there is significant difference in vertical ground reaction force(p<0.001).When going uphill,the vertical ground reaction force at other angles decreases as the angle increases compared to 0 °;When ascending a slope,the vertical ground reaction force at other angles increases as the angle increases compared to 0 °.Conclusion:During uphill and downhill running,as the angle increases,the Patellofemoral Joint Force and the Patellofemoral Joint Stress are the result of the joint action of the knee flexion angle,the torso forward inclination angle,and the vertical ground reaction force.During uphill running at 0 ° to 3 °,the torso forward inclination angle plays a major role in causing the patellofemoral joint stress to decrease.After 3 °,as the angle increases,the knee flexion angle plays a major role in causing the patellofemoral joint force,The increase of patellofemoral joint stress;During downhill running,as the slope angle increases,the knee flexion angle increases,the torso forward inclination angle decreases,and the vertical ground reaction force increases,resulting in an increase in patellofemoral joint force and patellofemoral joint stress.The results of this study also suggest that moderately increasing the torso forward tilt angle can reduce the stress of the patellofemoral joint of the knee joint and reduce the risk of knee injury during slope running and uphill running with small slope angles. |
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