| Background:Knee osteoarthritis(KOA)is a common degenerative disease in clinic.About 8.1%of people worldwide suffer from knee osteoarthritis,which predisposes to people over 50 years old.A large number of studies have used surface electromyography(sEMG)technology to explore abnormal neuromuscular motor patterns in patients with primary KOA,and to improve symptoms by improving abnormal motor patterns.Previous studies on quadriceps femoris(QF)sEMG have generally focused on the comparison between KOA patients and healthy people,and less on the differences between lower limbs on both sides of the patients.In addition to pain,one of the most common symptoms of osteoarthritis patients is fatigue,but it is the most easily overlooked,and about 40%of patients aged 65 and over reported clinically significant fatigue.Fatigue can alter the biomechanical and neuromuscular factors associated with the risk of musculoskeletal injury.Most studies on muscle fatigue in KOA patients have focused on muscle strength,endurance,and frequency distribution of emg signals,and few studies have explored the effect of fatigue on the coordinated movement patterns of different muscles in the quadriceps femoris of KOA patients.Objective:To compare the difference of sEMG characteristics of quadriceps femoris between the healthy side and the affected side in patients with KOA in the process of up stairs and down stairs.To explore the effects of fatigue training on the activation time of medial vastus muscle relative to musculus vastus lateralis and rectus femoris,the activation ratio of medial vastus muscle to musculus vastus lateralis,and to compare the variation of each index before and after fatigue of both legs.Methods:26 KOA patients(13 males,mean age 53.20±4.54 and 13 females,mean age 55.46±6.00)were enrolled in this experiment.The sEMG of the medial vastus muscle(VM),the musculus vastus lateralis(VL)and the rectus femoris in both side were recorded while the subjects completed the upper and lower steps.An accelerometer is placed on the outside of both heels,and the motion acceleration is recorded synchronously with the sEMG.Then the resistance fatigue training of quadriceps femoris was carried out:Resistance knee stretching was performed alternately with both legs,and fatigue was defined when the subjects could not reach the end of the knee again or when the knee could not maintain stability and the knee trembled.Finally,the second test,namely the sEMG test of upper and lower steps under fatigue condition,is carried out.Calculation index:(1)Relative activation time of medial vastus muscle relative to musculus vastus lateralis and rectus femoris(VM-VL,VM-RF)(Relative activation time=medial vastus muscle activation time-musculus vastus lateralis/rectus femoris activation time.If the difference is positive,it means that the medial vastus muscle is activated prior to the musculus vastus lateralis/rectus femoris;if the difference is negative,it means that the medial vastus muscle is activated later than the musculus vastus lateralis/rectus femoris)and the variation of relative activation time before and after fatigue AVM-VL、AVM-RF.(2)The activity degree ratio of the medial vastus muscle to the musculus vastus lateralis within 150ms before the moment when the foot contacts the step(the initial peak of the z-axis of the accelerometer)was calculated as the VM/VL activation ratio and the variation of activation ratio before and after fatigue △VM/VL was calculated.The ideal activation ratio should be close to 1,representing the coordinated movement of medial vastus muscle and musculus vastus lateralis.Result:(1)During un-fatigue condition,When walking up the steps,the activation time of medial vastus muscle relative to musculus vastus lateralis on the affected side was negative,indicating that the medial vastus muscle was activated after the musculus vastus lateralis,while the medial vastus muscle of the healthy side was activated earlier than the musculus vastus lateralis.There was significant difference between the two sides(T=-2.165,P=0.035).Both medial vastus muscle were activated later than rectus femoris,but there was no significant difference between the two sides(T=-0.410,P=0.684).When walking down the steps,there was no significant difference in relative activation time of VM-VL and VM-RF between the two legs(VM-VL:1=1.364,P=0.179;VM-RF:T=1.257,P=0.215).During fatigue condition,when going up the steps,the VM-VL activation time of the affected leg was later than that of the healthy leg(T=2.305,P=0.030),but there was no significant change in the healthy leg(T=-0.493,P=0.626).The relative activation time of VM-RF on both sides was significantly earlier(affected side T=-19.200,P=0.000,healthy side T=-25.197,P=0.000),but there was no significant difference between the two sides.The △VM-VL of affected leg was significantly reduced,with a significant difference from the healthy leg(T=-2.223,P=0.031),while the △VM-RF of bilateral legs had no significant difference(T=0.23 5,P=0.815).During fatigue condition,when going down the steps,the relative activation time of VM-VL on both sides did not change significantly compared with that before fatigue(affected side T=1.649,P=0.112,healthy side T=0.225,P=0.824).The relative activation time of VM-RF on both sides was significantly earlier than that before fatigue(affected side T=-16.570,P=0.000,healthy side T=-12.767,P=0.000),that is,the medial vastus muscle was activated before rectus femoris in fatigue state.And there was no significant difference in △VM-VL and △ VM-RF between the two legs(△VM-VL:T=-1.397,P=0.169,△VM-RF:T=-0.392,P=0.697).(2)During un-fatigue condition,When walking up the steps,the VM/VL activation ratio of the affected leg was significantly lower than that of the healthy leg(T=-3.577,P=0.000).The medial vastus muscle of the affected leg was less active than the musculus vastus lateralis,while the medial vastus muscle of the uninjured leg was more active than the musculus vastus lateralis.When walking down the steps,there was no significant difference in VM/VL activation ratio between the two legs(T=-0.382,P=0.703),but the activation degree of medial vastus muscle was higher than that of musculus vastus lateralis.During fatigue condition,After fatigue training,when going up the steps,the VM/VL activation ratio of affected leg decreased significantly(T=3.088,P=0.004),and the activation degree of medial vastus muscle and musculus vastus lateralis was more different.The VM/VL activation ratio of healthy leg decreased significantly(T=2.554,P=0.017),and the difference of activation degree between medial vastus muscle and musculus vastus lateralis decreased.There was no significant difference in variation of activation ratio △VM/VL between the two legs(T=0.036,P=0.971).After fatigue training,when going down the steps,there was no significant change in VM/VL activation ratio on both sides(affected side T=-0.150,P=0.882,healthy side T=1.963,P=0.061).There was no significant difference in variation of activation ratio △VM/VL between the two legs(T=-0.962,P=0.340).ConclusionWhen walking up the steps,in KOA patients,the activation time of medial vastus muscle of affected leg was later than that of musculus vastus lateralis,and the activation degree of medial vastus muscle was also lower than that of musculus vastus lateralis.Fatigue can aggravate the discordance of quadriceps femoris movement in KOA patients when they go up and down the steps.As the most easily neglected symptom,the abnormal influence of fatigue on knee joint movement pattern can not be ignored. |
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