Objective To observe the effect of knee isometric training on mild to moderate lower limb muscle spasticity in stroke patients.Methods A total of 130 stroke hemiplegia patients were prospectively included in this study.They were admitted to Xiangcheng People's Hospital of Suzhou City between August 2021 and December 2023 and numbered according to the order of collection.The patients were then randomly assigned to either the control group or the isokinetic group using a random number table.Each group consisted of 65 cases.Both groups underwent conventional rehabilitation training(5 days a week,40 minutes per day),with the isokinetic group receiving additional isokinetic muscle training(5 days a week,20 minutes per day)on top of the conventional rehabilitation training.The treatment period lasted for 6 weeks.The surface electromyographic signals of the rectus femoris muscle on the affected side were analyzed for their root-mean-square(RMS),integral electromyographic(iEMG)values,the modified Ashworth scale(MAS)scores,knee flexors and extensors peak torque and its ratio,the Fugl-Meyer assessment scale-lower extremity(FMA-LE)scores,and the 10 m walk test were used before and after the treatments to compare the surface electromyography of rectus femoris,the degree of muscle spasticity and exercise capacity of the lower extremities of the two groups.Results Prior to treatment,there were no statistically significant differences between the two groups in terms of the RMS of the rectus femoris muscle,iEMG values,MAS scores,peak torque of the flexor and extensor muscles and their ratio,FMA-LE score,and step speed(all P＞0.05).RMS of the rectus femoris muscle,iEMG values,MAS scores,peak torque of the knee flexors and extensors and their ratios,FMA-LE scores,and step speed improved in control group after treatment compared to before treatment([12.3±2.2]μV vs.[15.5± 2.9]μV,[24.8±2.3]μV·s vs.[29.2±3.1]μV·s,[1.34±0.15]points vs.[1.56± 0.25]points,[20.8±3.4]N·m vs.[12.3±2.5]N·m,[34.5±2.3]N·m vs.[26.3±3.6]N·m,0.60±0.16 vs.0.47±0.14,[26.1±2.9]points vs.[21.3±2.4]points,[0.61±0.14]m/s vs.[0.46±0.15]m/s;all P＜0.05).Rectus femoris muscle RMS,iEMG values,MAS scores,peak torque of the flexor and extensor muscles and their ratio,FMA-LE scores and step speed after treatment in the isokinetic group were(10.9±1.8)μV,(22.4±2.1)μV·s,(1.25±0.18)points,(28.7±3.0)N·m,(41.5±2.8)N·m,0.69±0.18,(29.0±2.3)points,(0.69±0.18)m/s,compared with pretreatment(respectively[15.4±2.2]μV,[29.6±3.0]μV·s,[1.58±0.34]points,[12.6± 2.3]N·m,[26.1±3.1]N·m,0.48±0.17,[21.5±2.1]points,[0.48±0.17]m/s)and control group after treatment,the differences were statistically significant(all P＜0.05).Before treatment,the differences in rectus femoris muscle RMS and iEMG values between patients with mild spasticity and patients with moderate spasticity in the isokinetic group and the corresponding patients with mild spasticity and moderate spasticity within the control group were not statistically significant(all P＞0.05).After treatment,the rectus femoris muscle RMS and iEMG values in patients with mild spasticity within the isokinetic group([10.2±1.0]μV and[20.2±2.0]μV·s,respectively)were statistically different from those before treatment([14.1±2.3]μV and[28.1±3.2]μV·s,respectively)and those after treatment in patients with mild spasticity within the control group([11.4±1.7]μV and[23.6±2.5]μV·s respectively;all P＜0.05);the rectus femoris muscle RMS and iEMG values in patients with moderate spasticity within the isokinetic group improved compared with the pre-treatment period([11.8±1.5]μV vs.[16.9±2.6)μV,and[24.9±2.2]μV·s vs.[31.3±3.8]μV·s,respectively;both P＜0.05),and with the control group after treatment(RMS and iEMG values of[13.2±2.5]μV and[26.1± 2.7]μV·s,respectively),the difference in RMS was statistically significant(P＜0.01),and the difference in iEMG values was not statistically significant(P＞0.05).Conclusion Isokinetic muscle training has a positive effect on improving mild-to-moderate muscle spasticity of the lower limb knee extension,and the effect is more significant the lighter the degree of spasticity.