Influence of different depths and loads on knee joint mechanics and peripheral muscle force characteristics during squatting

Yan Xiangning; Chen Lei; Chen Yonghuan; Wang Chao; Li Xiaosheng

doi:10.12307/2025.829

Abstract：BACKGROUND:There are many variations and techniques of squatting in sports,and different squatting methods will have different effects on knee mechanics.Existing research results lack a full discussion concerning the effects of different depths and loads on the mechanical changes of the knee joint during squatting. OBJECTIVE:To investigate the knee biomechanical characteristics of three different depths(shallow,parallel and deep squat)under three loads:85%,50%,and 0%of 1 repetition maximum,in order to provide a scientific evidence for choosing a reasonable depth and load for squatting training. METHODS:Kinematic,kinetic,and electromyographic data from 15 male subjects taking squats with different squat depths and loads were synchronously collected using a high-speed video camera(Sony),a three-dimensional force platform(Kistler),and an electromyograph(Noraxon).Inverse kinetics,biomechanical musculoskeletal modeling,and optimization algorithms were used to compute knee joint mechanics and lower limb muscle group force.Lastly,a two-way analysis of variance was employed to analyze the differences between the different depths and load conditions. RESULTS AND CONCLUSION:(1)The main effect of load on knee joint moment was significant(P＜0.01).The shallow,flat,and deep squats all had the smallest knee moments at 0%load.(2)The main effect of loading on tibiofemoral joint force,patellofemoral joint force,and cruciate ligament force was significant(P＜0.01).With the increase of squat depth,the curves of tibiofemoral joint force,patellofemoral joint force,and cruciate ligament force showed a bimodal trend.(3)The main effect of loading on quadriceps force,hamstring force,and gastrocnemius force was significant(P＜0.01).50%loading had the greatest quadriceps force,and hamstring and gastrocnemius forces were greatest at 85%loading.With the increase of depth,the change of quadriceps and hamstring muscle force showed a bimodal trend,while the gastrocnemius muscle force showed a trend of decreasing and then increasing.(4)Various mechanical parameters of the knee joint increased with increased loading,but the difference between 50%and 85%loading was small.All three depths of squatting showed maximum patellofemoral joint force and quadriceps force at 50%loading.The posterior cruciate ligament force,hamstring force,and gastrocnemius muscle force all reached their maximum at 85%loading.The increase in squatting in depth had no significant effect on the posterior cruciate ligament force.When the aim was to maximize the development of the muscle strength for the weighted squat,the 50%loaded parallel squat is recommended,but consider that it results in greater joint and ligament forces.