屈膝肌疲劳对单腿落地时下肢生物力学指标的影响

Effects of Knee Flexor Fatigue on Lower Limb Biomechanics during Single-Leg Landing

目的:探讨不同程度屈膝肌疲劳对女性大学生跳跃后单腿落地时下肢生物力学指标的影响。方法:对16名女性大学生利用等速肌力测试系统进行屈膝肌疲劳诱导,分别在疲劳前以及诱导疲劳后最大屈膝力矩下降至75%、50%、25%时进行跳跃落地测试,同步采集落地过程中下肢运动学、动力学及肌电数据。结果:(1)屈膝肌疲劳对跳跃初始落地后100 ms内半腱肌、股二头肌、腓肠肌肌电活动有显著影响(P=0.000,P=0.006,P=0.017)。当最大屈膝力矩下降至50%时,半腱肌平均振幅较疲劳前及下降至75%时显著降低(P=0.001,P=0.016),当最大屈膝力矩下降至25%时半腱肌平均振幅较疲劳前、下降至75%和下降至50%时显著降低(P=0.000,P=0.001,P=0.006)。当最大屈膝力矩下降至50%时股二头肌平均振幅较下降至75%时显著降低(P=0.000),而下降至25%时股二头肌平均振幅较疲劳前、下降至75%和下降至50%时显著降低(P=0.008,P=0.000,P=0.033)。腓肠肌平均振幅在最大屈膝力矩下降至25%时较疲劳前及下降至75%时显著降低(P=0.024,P=0.018)。(2)屈膝肌疲劳对初始落地时刻髋、膝关节屈曲角度和地面反作用力峰值时刻的髋、膝关节屈曲角度有显著影响(P=0.010,P=0.044,P=0.010,P=0.005);初始落地时刻在最大屈膝力矩下降至50%和25%时髋关节屈曲角度较疲劳前显著降低(P=0.012,P=0.021),膝关节屈曲角度较疲劳前显著降低(P=0.029,P=0.024);地面反作用力峰值时刻在最大屈膝力矩下降至50%和25%时髋关节屈曲角度较疲劳前显著降低(P=0.011,P=0.026),膝关节屈曲角度较疲劳前显著降低(P=0.005,P=0.006)。(3)屈膝肌疲劳对初始落地时刻膝关节伸展力矩具有显著影响(P=0.011);当最大屈膝力矩下降至50%和25%时膝关节伸展力矩显著高于疲劳前(P=0.033,P=0.013)。结论:屈膝肌疲劳对单腿落地时下肢生物力学指标有显著影响,随着屈膝肌疲劳程度加深,当屈膝肌最大力矩下降至50%时屈膝肌保护作用下降,跳跃落地时下肢动作即出现“僵硬化”现象,而下降至25%时这一负面变化同样存在,但未出现进一步改变。

ObjectiveTo explore the effect of knee flexor fatigue of different levels on lower limb biomechanics during the single-leg landing of female university students.MethodsSixteen female university students were recruited and induced fatigue of the knee flexion using a dynamometer.They underwent the single-leg landing test before fatigue as well as when their maximal knee flexion moment decreased 75%,50% and 25% after fatigue.The kinematics,dynamics and the electromyography data of lower limbs during the landing were collected simultaneously.Results(1)The knee flexor fatigue had significant effects on the electromyographic activity of the semitendinosus,biceps femoris and gastrocnemius within 100 ms after initial landing(P=0.000,P=0.006,P=0.017).At the maximal knee flexion moment of 50%,the semitendinosus activity was significantly lower than that before fatigue and at the maximal knee flexion moment of 75%(P=0.001,P=0.016).At the maximal knee flexion moment of25%,the semitendinosus activity was significantly lower than before fatigue,as well as at the maximal knee flexion moment of 75% and 50%(P=0.000,P=0.001,P=0.006).At the maximal knee flexion moment of 50%,the activity of biceps femoris decreased significantly compared with that at the maximal knee flexion moment of 75%(P=0.000).Moreover,the activity of biceps femoris at the maximal knee flexion moment of 25% was significantly lower than before fatigue,as well as at the maximal knee flexion moment of 75% and 50%(P=0.008,P=0.000,P=0.033).At the maximal knee flexion moment of 25%,the electromyographic activity of the gastrocnemius was lower than before fatigue and at the maximal knee flexion moment of 75%(P=0.024,P=0.018).(2)The knee flexion fatigue significantly affected the hip and knee flexion angles at the initial landing moment and the peak ground reaction force moment(P=0.010,P=0.044,P=0.010,P=0.005).At the maximal knee flexion moments of 50%and 25%,the flexion angle of the hip was significantly lower than before fatigue(P=0.012,P=0.021).The flexion angle of the knee at the initial landing moment was also significantly lower than that before fatigue(P=0.029,P=0.024).At the maximal knee flexion moment of 50% and 25%,the flexion angles of the hip and knee were significantly lower than that obtained before the fatigue(P=0.011,P=0.026;P=0.005,P=0.006) at the peak ground reaction force moment.(3)The knee flexion fatigue significantly affected the knee extension moment(P=0.011).At the maximal knee flexion moment of 50%and 25%,the knee extension moment was significantly lower than that found before fatigue(P=0.033,P=0.013).ConclusionThe knee flexor fatigue has significant effects on lower limb biomechanics during the single-leg landing.As the degree of the knee flexor fatigue increases,the protective effect of knee flexors decreases and the lower limbs appear stiff at the maximal knee flexion moment of 50%and 25%.