Association Between The Timing Of Lower Extremity Muscle Activity In Hemiparetic Gait And Walking Performance Of Stroke Patients

Objective: The present study compared the surface electromyography(sEMG)during gait of stroke patients with that of healthy controls in order to explore the abnormality of the temporal patterning of lower extremity muscle activity in hemiparetic gait.We also exam the relationship of the observed abnormal time parameters with the walking ability of stroke patients to describe the extent to which the abnormal timing of muscle activity in hemiparetic gait is associated with patients’ walking performance,hoping to provide an evidence-based reference and theoretical support for the occurrence and development of walking dysfunction after stroke and the selection of clinical therapeutic methods.Methods: 30 stroke patients and 11 healthy adults formed the stroke group and healthy control group,respectively.Both groups accepted the gait analysis on the treadmill.sEMG signals of rectus femoris(RF),biceps femoris(BF),gastrocnemius medialis(GM)and tibialis anterior(TA)of bilateral lower extremities of the subjects were recorded during the walking.The duration of the muscle activity and the duration of the cocontraction of agonist and antagonist were calculated during four subphases of the gait cycle,namely the initial double support(DS1),the single support(SS),the second double support(DS2)and the swing(SW),to quantify the temporal patterning of muscle activity.As for the stroke group,additional clinical tests were completed.Time-consuming of the Timed Up and Go test(TUGT)and maximal walking speed test(MWST),as well as the score of dynamic gait index(DGI)were recorded to quantify patients’ walking performance.The shorter time consumed to finish the MWST and TUGT,and the higher DGI score represent the better walking performance.Result:1.The results of the temporal characteristics of upper leg muscles showed the mean percentage of the duration of BF activity during DS1(60%),SS(54%)and DS2(40%)was significantly increased compared to controls(53%,42% and 23%,respectively).The abnormally long duration of BF activity during DS2 was also observed in nonparetic leg(34% versus 23% in controls).Contrary to these mentioned trends,the percentage of BF activity(47%)in the nonparetic leg of SW was decreased compared with controls(59%).Prolongation of RF activity during SS and DS2 were found on the paretic side(61% and 40%,respectively)as well as on the nonparetic side(57% and 37%,respectively)relative to the control group(50% for SS and 27%for DS2).The results of mean coactivation level showed that longer duration of paretic RF-BF coactivity could be seen during both DS1(42%)and SS(34%)when compared to controls(35% and 23%,respectively).The mean relative duration of RF-BF coactivity in the nonparetic leg were also significantly longer during SS(28%)and DS2(25%)compared to the control group(23% and 17%,respectively).2.The results of the temporal patterning of lower leg muscles showed that longer durations of paretic GM activity were observed during both DS1(56% versus 38% in controls)and SS(61% versus 50% in controls).TA on the paretic side showed asignificant increase in burst duration during both DS1(54%)and DS2(42%)when compared with the control group(47% and 30% respectively).During SW,the duration of TA activity were longer in both legs(64% in paretic leg and 61% in nonparetic leg)relative to control values(45%).The results of cocontraction level showed that the increased duration of TA-GM coactivity during DS1 was found in both the paretic leg(34%)and the nonparetic leg(29%),compared with the control group(19%).However,during the SS,only the duration of paretic TA-GM coactivity(30%)was longer than that of the control group(22%).3.The correlation between timing of muscle activity during gait and walking performance showed that duration of paretic RF activity during SS(r=0.432 with TUGT,r=-0.376 with DGI),duration of paretic BF activity during SS(r=-0.419 with DGI,r=0.395 with TUGT,r=0.444 with MWST),duration of nonparetic RF-BF coactivity during DS2(r=-0.362 with DGI,r=0.384 with TUGT,r=0.390 with MWST),duration of paretic RF activity during DS2(r=0.440 with TUGT,r=0.397 with MWST)and duration of paretic TA-GM coactivity during DS1(r=-0.392 with DGI,r=0.366 with MWST)are the five parameters which showed significant difference with those of the control group.The closer the value of these parameters is to the controls,the better the walking performance.Duration of nonparetic BF activity during DS2(r=-0.381 with MWST),duration of paretic RF-BF coactivity during DS1(r=-0.430 with TUGT,r=-0.497 with MWST)and duration of nonparetic RF-BF coactivity during SS(r=0.471 with DGI,r=-0.380 with MWST)were also significantly different from those of the control group,but the more these parameters deviated from the controls,the better the walking performance of the patients has.Conclusion:1.Compared with the healthy controls,both the muscles of paretic and nonparetic leg of stroke patients showed significant abnormalities in the burst duration and coactivation duration.But most of the abnormal temporal patterning(14/22)were not correlated with the short-distance walking performance of the patients.2.Compared with the healthy controls,stroke patients showed an increase in the duration of BF during DS2 on the nonparetic side,the coactivation duration of paretic RF-BF during DS1 and coactivation duration of nonparetic RF-BF during SS.However,these three abnormal timing of muscle activity enhanced the short-distance walking performance of stroke patients as a compensation.3.Increased burst duration of paretic RF during SS,paretic BF during SS,paretic RF during DS2,and the increased coactivation duration of nonparetic RF-BF during DS2,paretic TA-GM during DS2 will hinder the walking performance of patients.The improvement of the timing of these muscle activities in the corresponding gait phases during clinical treatment can improve the short-distance walking speed and dynamic balance of stroke patients..