| Objective:Squats are popular in sports,squats have a variety of variants and techniques,different squat methods will have different effects on knee joint mechanical variables,combined with the influence of knee joint mechanical variables when squatting at different depths and loads has not been fully studied.This paper will test and analyse the biomechanical variables of the knee joint at three different depths of squat(shallow,parallel and deep squat)at three different loads(85%,50% and 0% 1RM)to provide a scientific basis for selecting the appropriate depth and load for squat training.Methods:Eight male subjects from the Xi’an Physical Education University were recruited to participate in the experiment.Use a Sony camera to collect kinematic data(50Hz);Kinetic data(1000Hz)were obtained using the Kistler 9287 B 3D force plate;Use the Noraxon Ultium EMG System to acquire lower limb muscles EMG.Inverse kinetics,biomechanical muscle models,EMG-driven and optimization algorithm were used to calculate joint moments,patellofemoral forces,tibiofemoral forces and cruciate ligament forces.Two-way ANOVA was used to compare the differences in biomechanical parameters of the knee joint at different depths and loads.Results:(1)One-way ANOVA on the 1RM at each depth revealed that although the shallow squat was greater than either of the latter two,there was no significant difference between the three(p>0.05).A two-way ANOVA showed that the interaction of depth and load on each joint angle was not significant(P > 0.05).The main effect of depth was significant(P < 0.01)for each joint angle at the same load,except for the ankle angle.The main effect of load was not significant(P > 0.05)for each joint angle at the same depth.(2)The main effect of knee moment was not significant for depth at the same load(P > 0.05).The main effect of load was significant for knee moments at the same depth(P < 0.01).The knee moment was greatest for the deep squat at all different depths under the same load,which was not statistically significant(P > 0.05).All three were maximal at 50% 1RM load state under different loads at the same depth,and the knee moments of the shallow squat at its 85% 1RM load state and the shallow squat at its 50% 1RM load state were significantly different from the knee moments of the shallow squat at no load state,respectively(P < 0.05).(3)The peak tibiofemoral joint force,patellofemoral joint force and cruciate ligament force were affected by different loads and depths,and two-way ANOVA showed that the interaction between depth and load on the internal forces and ligaments forces of each joint was not significant(P>0.05).At the same depth of the internal forces of each joint,the main effect of the load was significant(P<0.01).(4)Two-way ANOVA showed that depth and load did not have significant effects on the interaction of muscle forces(P>0.05).At the same depth,the main effect of the load was significant(P<0.01).Under the same load,the main effect of depth was not significant(P>0.05).Conclusions:(1)Knee moments increased with increasing load,but the effect on knee moments was almost identical when performing weighted squats;different depths did not affect peak knee moments and deep squats produced higher moment loading rates during the movement.(2)When performing all three types of squats,shallow squats have the highest tibiofemoral force,deep squats have a sudden increase and decrease in tibiofemoral force,while shallow and parallel squats have stable tibiofemoral force.(3)Weighted squats exert a lower force on the quadriceps and hamstrings,but weighted shallow squats and parallel squats will produce greater patellofemoral forces than weighted squats.(4)Posterior cruciate ligament forces increase with increasing load.Squat depth does not have a significant effect on posterior cruciate ligament forces. |
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