| Background and objective:The knee extensor mechanism refers to the convergence of the four quadriceps muscles into the quadriceps tendon,which is attached to the proximal patella and extends distally to the tibial tuberosity through the patellar tendon.The quadriceps muscle and patellar tendon are important components of the knee extensor mechanism and play an important role in supporting stability and movement.Lesions of the quadricep muscle and patellar tendon often occur in specific localized areas,and enhanced assessment of their stiffness can monitor and reflect their functional status.Appropriate reduction in muscle stiffness can reduce the risk of musculotendinous injury in sports and rehabilitation settings.Self-Myofascial Release(SMR)and Static Stretching(SS)are often used to improve range of motion(ROM),reduce stiffness of the musculotendinous unit,and prevent sports-related injuries.However,the immediate and prolonged effects of SMR and SS training on the stiffness of specific regions of the quadricep muscle and patellar tendon and the ROM of the flexed knee are still unknown.Two experiments were conducted in this study.First,we investigated the changes and inter-regional differences in region-specific stiffness of quadricep muscle(RF,VM,and VL)and patellar tendon(PPT,MPT,and DPT)at different knee flexion angles and further assessed the reliability of the digital muscle function assessment system Myoton PRO assessment to quantify the stiffness of soft tissues such as lower limb muscles and tendons.We then explored the immediate and prolonged effects of SMR training versus SS training on region-specific stiffness of the quadricep muscle(RF,VM,and VL)and patellar tendon(PPT,MPT,and DPT),and knee flexion ROM.Methods:Experiment 1: Thirty healthy subjects were included,and assessors A and B applied Myoton PRO to quantitatively assess the stiffness of the subject’s dominant lower extremity RF,VM,VL,PPT,MPT,and DPT in the 45°,90°,and 135° positions of knee flexion on the same day(30 min apart before and after).After seven days,assessor A repeated the above assessment operation at the same time and place.Experiment 2: The 90 healthy subjects were randomly and equally divided into the SMR,SS,and control groups.The SMR group underwent three sets of 1-minute(30 s of rest between each set)SMR training,and the SS group underwent three sets of 1-minute(30 s of rest between each set)SS training.The control group was treated with 5 minutes of sedentary rest.The changes in RF,VM,VL,PPT,MPT,and DPT stiffness and knee flexion ROM of the subject’s dominant lower extremity were assessed before,immediately after,5 minutes later,and 10 minutes after the intervention,respectively.Results:Experiment 1: 1)For the healthy subject population,the inter-assessor(ICC ≥0.62)and intra-assessor reliability(ICC ≥ 0.71)of Myoton PRO quantitative assessment of quadricep muscle(RF,VM,and VL)and patellar tendon(PPT,MPT,and DPT)specific region stiffness were good to excellent;2)There was no statistically significant difference(P > 0.05)between RF,VM and VL stiffness in the45° to 90° flexed knee position,but all three regions stiffness increased significantly(P < 0.05)in the 135° flexed knee position.3)stiffness of all regions of the patellar tendon increased significantly with increasing knee flexion angle(P<0.05),while MPT and DPT stiffnesses were not statistically different at different knee flexion angles(P>0.05),but PPT stiffness was significantly higher than MPT and DPT stiffness at different knee flexion angles(P < 0.05).Experiment 2: 1)Both SMR intervention and SS intervention significantly increased knee flexion ROM(P < 0.05),and this change lasted until after 10 minutes after SMR,but only until after 5 minutes after SS;2)The effect of RF stiffness reduction by SMR intervention lasted until after 10 minutes,but the reduction of RF stiffness by SS intervention had only a brief,immediate effect(P < 0.05);3)SMR intervention significantly reduced both VM and VL stiffness immediately after the intervention(P < 0.05),but VM and VL stiffness did not change after the SS intervention(P > 0.05),and VM stiffness was significantly lower than that of the SS group at all time points after the SMR intervention(P < 0.05);4)PPT stiffness was significantly reduced immediately after both the SMR and SS interventions(P < 0.05);5)Both the SMR and SS interventions,there was no change in the stiffness of both MPT and DPT(P > 0.05).Conclusions:1)Myoton PRO is a reliable device for assessing the stiffness of specific regions of the quadricep muscle and patellar tendon;patellar tendon stiffness increased with increasing knee flexion angle,but quadriceps muscle stiffness increased only after a knee flexion angle greater than 90°;2)patellar tendon stiffness was nonhomogeneous in its longitudinal axis,and proximal patellar tendon stiffness was significantly higher than other regions;3)both SMR training and SS training reduced region-specific stiffness of the knee extensor mechanism and improved the knee flexion ROM,and SMR training was more effective than SS training. |
