| Objective:The exercise prescription to enhance Vastus Medialis muscle strength and its dysfunction as patellofemoral pain syndrome prehabilitation strategy was not consistent on the selection type of exercise and depth of knee flexion.This study was aimed to explore different knees Angle(15°,30°,45°,60°)and different type of exercise's(single leg squat,lunge,back squat)surface electromygraphy,(s EMG)on the VMO and VL activation.So that the optimum range of motion of knee flexion and type of exercise can be identified to serve mass sports population scientific training basis.Methods:16 healthy college students(age 22.38±2.03,height 168.59±6.75,weight 60.5±10.42,BMI 21.18±2.61)were selected.All participants had met the inclusion criteria.The participants were randomly completed 12 sets of combination sequence of depth of knee flexion(15°,30°,45°,60°)and different type of exercises(single leg squat,lunge,back squat).Each test condition was successfully tested 3 trails with 2 minutes of rest in between trails.Using the Surface Electromyography System(1500HZ),the original electromyogram of VL and VMO and the kinematics parameters of the knee joint were recorded with three dimensional joint angles.The mean square amplitude(MVIC normalization)of VL and VMO in each movement at the targetted angle and VMO:VL ratio were computated.This study incorporated cross over repeated design,SPSS22 was used to carry out the 2-ways repeatment measure of analysis of variance for all dependent variables and the statistical significance level was p<0.05.Results: 1)The knee flexion angle and type of exercise for VL,VMO activation level and VMO:VL ratio were statistically significant(p<0.05).2)The interaction effect between knee flexion angle and type of exercise for VL and VMO activation level were statistical significant(p<0.05),but not for VMO: VL ratio.3)For VL,knee flexion angles were statistically significant(p<0.05).The VL activation were greater with increasing knee flexion angle,thus 60°>45°>30°>15°.In term of type of exercise,VL activation were greater in single leg support than double leg support type of exercises.Therefore,single leg squat>lunge>back squat.4)For VMO,knee flexion 15°,30°,45° and 60° were statistical significance different(p<0.05);Single leg squat and lunges,and back squat were statistical significant differences(p<0.05),while lunge and back squat were no statistically significant different(p>0.05).5)For VMO:VL ratio,all knee flexion angles were statistically significant differences(p <0.05)except comparison between knee flexion 30° and knee flexion 45° were no statistically significant difference(p>0.05).While knee flexion 45° was the greatest value;the trend were of 45°>60 °>30 °>15 °;As comparison between type of exercise,back squat were statistically significant different to lunge and single leg squat(P<0.05),but single leg squat and lunge were no statistical significant difference between each other.However the trend were single leg squat>lunge>back squat.Conclusions 1)VL and VMO activation level were affected by the depth of knee flexion,from 0° to 60°knee flexion range the VMO and VL activation levels increase with the increase of the depth of the knee flexion,both level of largest activated were at knee flexion 60°.2)From the perspective of VL level of activation,single leg squat > back squat >lunge,indicating that there are a progressive relationship between the three movements,in term of VMO activation level,single leg squat > back squat and lunge,shown progressive relationship in level of VMO activation between single leg squat and back squat,and lunge,VMO:VL ratio shown single leg squat or lunge is higher level of activation than back squat.3)The greatest the angle of the knee flexed,VMO:VL ratio is closer to 1,but after the optimal activation angle,the ratio decreases.4)While knee flextion at 45°,only single leg squat met the strength development requirement whereas the other two exercises met the muscular endurance development or muscular activation requirement. |
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