Effects of Hip Adduction and Abduction Forward Lunge on Muscle Activity and Center of Pressure in Healthy Subjects: A Pilot Study

Patellofemoral pain syndrome (PFPS) ranks among the most prevalent factors causing anterior knee pain. Quadriceps exercises such as forward lunges are important to treat PFPS. Aim: We investigated whether there is a difference in muscle activity between the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles and the center of pressure (CoP) among three hip positions, namely, hip adduction forward lunge (HADF), hip neutral forward lunge (HNEF), and hip abduction forward lunge (HABF), in healthy subjects. Method: This was a randomized controlled pilot study that included twenty healthy (age: 23.7 ± 2.51) volunteers. The CoP was measured using a “Wii Balance Board” from Nintendo, and VMO and VL muscle activity were measured via wireless surface electromyography. Results: The CoP outcomes showed significant differences among the three positions in terms of position (p < 0.001), sum distance (p < 0.001), range (p < 0.001), and max distance (p < 0.001). VMO (p < 0.000), and VL (p < 0.005) muscle activity and the ratio of VMO/VL (p < 0.000) significantly differed among the three positions. Conclusions: Although VMO and VL muscle activity increased in the HADF and HABF, excessive changes in the CoP occurred in the two positions. The change in the CoP during the HADF and HABF may result in valgus, varus, and loading of the knee joint, which may worsen PFPS. The HNEF is recommended for quadriceps strengthening in healthy subjects and PFPS patients.