Effects of muscle strength training combined with neuromuscular electrical stimulation on pain, function, muscle strength, patellar stress, and muscle activation during running in people with patellofemoral pain

Objective This study aimed to investigate the effects of a 6-week muscle strength training combined with neuromuscular electrical stimulation on pain, function level, muscle strength, patellar stress, and muscle activation during running among individuals with patellofemoral pain (PFP). Methods This study is a randomized, controlled, and assessor-blinded trial. Fifty-eight PFP participants were randomly assigned to the neuromuscular electrical stimulation combined with muscle strength training (EMS), conventional muscle strength training (MST) and health education (HE) groups. They received EMS, MST and health lectures series, respectively, for 6 weeks. Pain scores, knee function levels of anterior knee pain scale (AKPS), muscle strength of quadriceps, patellofemoral joint stress (PFJ), and muscle activation of vastus medialis oblique (VMO) and vastus lateralis (VL) during running were measured at week 0 and week 7, respectively. Two-way (group by time) ANOVA with repeated measures was used to evaluate training effects. Results Significant interactions were detected in pain score, AKPS, muscle strength, PFJ and muscle activation of VMO and VL. Compared with week 0, the pain score and PFJ decreased, whereas the AKPS, quadriceps muscle strength, muscle activation of VMO and VMO:VL ratio increased in EMS and MST groups at week 7. Additionally, the AKPS and muscle activation of VMO:VL ratio were significantly increased in the EMS group at week 7 compared with the MST and HE groups. Conclusion EMS could be recommended as one of the clinical treatments for PFP to relieve pain, improve knee function, and balance muscle activation of VMO and VL, thereby decrease patellofemoral joint stress during running. Trial registration: The effects of muscle electrical stimulation combined with muscle training on patients with joint pain and biomechanical characteristics of lower limbs, ChiCTR2300067598. Registered 13 January 2023, https://www.chictr.org.cn/showproj.html?proj=180778