Effects Of Combining Electrical Muscle Stimulation With Strength Training On Lower Limb Mechanics With PFPS

Patellofemoral pain syndrome (PFPS) is a common causative factor of knee pain. Exercise and electrical muscle stimulation (EMS) have been shown to improve knee function and relieve pain in patients with PFPS. However, the effect of exercise and EMS training on lower limb mechanics is unclear. PURPOSE: To quantify the lower limb mechanics during single-leg squats following 6-week training interventions. METHODS: 46 participants were recruited and randomly assigned into the muscle strength training (MST) group (21.5 ± 3.8 yr, 174.7 ± 8.4 cm, 69.5 ± 11.7 kg) and combining EMS with strength training (EMS) group (22.2 ± 4.3 yr, 173.8 ± 7.4 cm, 72.4 ± 13.2 kg). Lower limb mechanics during single-leg squats were collected at the baseline and following the 6-week intervention for each group by using infrared motion capture systems and force platform. Two-way (group by time) analysis of variance with repeated measures were applied to determine the effect of training on the lower limb mechanics. RESULTS: Significant interactions were detected in peak patellofemoral joint stress (P = 0.020), during single-leg squat. Post-hoc indicated that compared with week 0, peak patellofemoral joint stress (EMS: from 0.033 ± 0.006 to 0.024 ± 0.004 MPa/kg, P < 0.001; MST: from 0.031 ± 0.006 to 0.027 ± 0.005 MPa/kg, P = 0.033) decreased at week 6. And the EMS group demonstrated greater changes in decreasing peak patellofemoral joint stress (P = 0.036), compared to the MST group following training. Training resulted in significantly smaller knee extension moment (EMS: from 1.393 ± 0.278 to 1.148 ± 0.211 Nm/kg, MST: from 1.365 ± 0.287 to 1.271 ± 0.300 Nm/kg, P = 0.001), knee abduction moment (EMS: form 0.567 ± 0.156 to 0.476 ± 0.127 Nm/kg, MST: form 0.543 ± 0.179 to 0.503 ± 0.150 Nm/kg, P = 0.030), knee external rotation moment (EMS: form 0.028 ± 0.079 to 0.000 ± 0.065 Nm/kg, MST from 0.029 ± 0.079 to 0.001 ± 0.056 Nm/kg, P = 0.045), during single-leg squat. CONCLUSIONS: EMS training is beneficial for altering knee movement patterns and joint loading during single-leg squats in patients with PFPS compared to MST.