Effect of muscle strength exercise on surface electromyography over thigh in stroke patients with hemiplegiaduringconvalescence

Objective To explore the effect of muscle strength exercise on surface eleetromyography （sEMG） over thigh in stroke patients with hemiplegia during convalescence so as to gain objective evidence for rehabilitation therapy of stroke patients. Methods Thirty-five stroke patients with hemiplegia during convalescence were enrolled in this study, and were divided into two groups, treatment group （n=19） and control group （n=16）. The treatment group underwent muscle strength exercise for 6 weeks. Before and after treatment, sEMG signals over vastus medialis （VM）, rectus femoris muscle （RF）, vastus lateralis （VL）, biceps femoris （BF） and semitendinosus （ST） and semimembranosus （SM） during maximal isometric voluntary contraction （MIVC） of the affected knee extension and flexion were recorded. Torque of knee joint extension and flexion, root mean square （RMS） and co-contraction ratio （CR） were computed. No rehabilitation training was performed in control group. The above mentioned indexes of control group were also recorded. Results After treatment, obvious changes were observed in MIVC torque of the affected knee flexion [ （18.02±6.52） nm vs （13.12±5.79） nm, P〈0.05] and extension [ （45.72±17.21） nm vs （34.76±17.19） nm, all P〈0.05 ]. There were no significant differences in CR of flexion and extension. No statistical difference was observed in MIVC torque and CR of flexion and extension before and after treatment in control group （all P〉0.05）. RMS value significantly improved when RF, VL, ST and SM over affected thigh were agonist after treatment [ （146.60±60.85） μV vs （97.02±57.17） μV, （172.65±60.73）μV vs （131.46±52.15） μV, （188.69±89.60） μV vs （130.57±73.76）μV, all P〈0.05]. There were no significant differences of RMS value in the VM and BF before and after treatment （all P〉O.05） , and no RMS changes were noted in control group （all P〉0.05）. Conclusions Strength exercise may improve strength of flexion and extension over lower limbs in stroke patients with hemiplegia during convalescence, however, it will not induce abnormal contraction of flexion and extension, sEMG combined with torque measurement may assess functional status of hemiplegic limbs effectively. Key words: Stroke;  Muscle strength exercise;  Convalescence;  Hemiplegia;  Electromyography