| Objective: Side-cutting is a rapid change of direction in sports.Among the many factors that affect the biomechanics of side-cutting,different foot strike patterns and angles will produce different loads on the knee joint,which are potential risk factors for anterior cruciate ligament injury.However,there is still a lack of consistent conclusions about the kinematics and kinetics of different foot strike patterns and angles.Therefore,the purpose of this study was to explore the basic regular characteristics of the biomechanical parameters relate to human lower limbs when performing side-cutting with different foot strike patterns and angles.Methods: 20 male ball sports enthusiasts who adopted rearfoot strike pattern were recruited(mean age is 22.4±2.5 years,height is 1.74±0.8m,and weight is75.2±10.5kg).First,the participants were asked to use rearfoot strike pattern to perform 45°,90°,and 135° side-cutting at the maximum speed,and then switch to the forefoot strike pattern to perform 45°,90°,and 135° side-cutting again.Eight Vicon infrared cameras and a kistler force plate were used to synchronously collect the kinematics and kinetics data of the subject during side-cutting.The sampling frequency was 200 HZ and 1000 HZ,respectively.Visual 3D software was used to further process the data,and all data were expressed as mean±standard deviation.All statistical analyses were conducted using statistical software(SPSS.20.0).Analysis of variance was conducted to examine the influence of average speed under different conditions.The paired-sample T test was used to analyze the kinematics and kinetics data of different foot strike patterns.A one-way analysis of covariance was used to compare the kinematics and kinetics data of different side-cutting angles.Bonferroni method was used for multiple comparisons.The significance level was set at p<0.05.Results:1.There was no significant difference in the average speed of different foot strike patterns.The average speed was lower when cutting to shaper angles(p<0.05).2.Peak joint angles: The rearfoot strike pattern had significantly higher maximum hip flexion,knee varus,and knee external rotation angles than the forefoot for all 45°,90° and 135° side-cutting(p<0.05),while the maximum ankle valgus and external rotation angles were lower than the forefoot strike pattern(p<0.05).For the45° or 90° side-cutting task,paticipants had decreased maximum hip extension and ankle plantarflexion angles with the rearfoot strike pattern(p<0.05),whereas they had decreased maximum knee flexion angle with the forefoot strike pattern(p=0.035).When performing 90° or 135° side-cutting,the rearfoot strike technique showed greater maximum hip adduction,hip abduction,and hip external rotation angles than the forefoot(p<0.05),while the maximum hip internal rotation,knee extension,knee valgus,ankle dorsiflexion,ankle inversion,and ankle internal rotation angles were lower than the forefoot strike pattern(p<0.05).The maximum hip abduction,knee flexion,and ankle varus angles decreased for both landing technique when cutting at 45° compared to 90° or 135°(p<0.05).3.Intial contact angles: When cutting at 45°,90° and 135°,the rearfoot strike showed greater hip flexion angle at intial contact(p<0.05),whereas the forefoot strike had higher ankle varus angle at intial contact(p<0.001).The ankle dorsi/plantar flexion angle at intial contact showed different motion states for both foot strke patterns(p<0.001).The rearfoot landing technique had decreased hip internal/external rotation contact angle(p=0.015),whereas the forefoot landing technique showed lower knee internal/external rotation angle at intial contact(p<0.001)when cutting at45°.The knee inversion/exversion,ankle internal/external rotation contact angles showed different motion states for both landing patterns(p<0.05).When cutting at90° or 135°,the rearfoot strike pattern presented decreased knee flexion and knee valugus angles at intial contact(p<0.05),and an increased the knee and ankle internal/external rotation angles at initial contact(p<0.05);The hip internal/external rotation contact angle was in different motion states in different landing patterns(p<0.001).Rearfoot and forefoot strikes showed sinificant lower hip abduction angle at peak and intitial contact when cutting to 45° compared to 90° and 135°(p<0.05).4.Joint moments: The rearfoot landing technique when compared with forefoot landing technique had significantly higher peak hip extension,knee flexion,knee extension,and ankle dorsiflexion moments(p<0.05),and decreased ankle plantarflexion and ankle varus moments(p<0.05)at all cutting angles.For 90° or 135°cutting task,the rearfoot strike pattern presented a lower peak hip flexion,knee external rotation,ankle internal rotation moments(p<0.05),and an increased peak hip adduction,knee valgus,and ankle external rotation moments(p<0.05)than the forefoot strike pattern.When cutting to 45° or 135° angle,the rearfoot strike pattern had a greater peak hip internal rotation moment(p<0.05).Both foot strike patterns had greater peak hip adduction,knee varus,knee internal rotation,ankle external rotation moments(p<0.05),and a decreased peak knee extension moment(p<0.05)in the cutting angles of 45° compared to the 90° or 135°.The forefoot landing technique showed greater peak hip abduction moment when cutting to 135°compared to 45° and 90°(p<0.05).The rearfoot landing technique presented lower peak ankle varus and ankle valgus moments when cutting to 45°compared to others cutting angles(p<0.05).5.Ground reaction force: The rearfoot strike pattern showed greater anterior,posterior and vertical ground reaction forces(p<0.05),and a decreased medial and lateral ground reaction forces(p<0.05)compare to forefoot strike pattern at all cutting angles.Both foot strike patterns had greater posterior ground reaction force(p<0.05),and lower medial ground reaction force(p<0.05)in the cutting angles of 135° compared to the 45° and 90°.The forefoot landing technique showed an increased anterior and verticial ground reaction forces(p<0.05),and a decreased lateral ground reaction force(p<0.05)when cutting to 45°compared to 90° and 135°.Conclusions: 1)The rearfoot strike pattern had lower knee flexion angle at intial contact.This means that the rearfoot strike pattern adopts a "hard landing" strategy,which mainly relies on the knee to absorb the impact and may increase the risk of ACL injury.The forefoot strike pattern showed greater peak angles and moments of ankle,which indicates that the forefoot landing technique was primarily dependent on the ankle to absorb load,thereby increasing the risk of ankle sprain.In addition,the forefoot landing mode had a larger hip internal rotation at peak and intial contact,which means that it will make more rotations of the hip.2)The hip abduction angle at peak and intial contact were higher when cutting to shaper angles,which may increase the knee valgus moment and lead to the risk of knee injury.In addition,the angles and moments on the frontal and horizontal planes of the knee and ankle were greater when cutting to shaper angles,which means that the load on the frontal and horizontal planes of the knee and ankle joints also increases. |
