A173: Effects of Lateral Resistance Lunge on Lower Limb Muscle Activation and Patellofemoral Joint Stress

Lunge exercises are often used in strengthening programs for patellofemoral pain syndrome (PFPS). However, limited data exist to evaluate the effects of lunge exercises with medial or lateral resistance on patellofemoral joint stress (PFJS) and lower limb muscle activation. The purpose of this study was to investigate the effect of three lunge exercises (Traditional lunge, TL; Lunge with hip adduction resistance, LHAD; Lunge with hip abduction resistance, LHAB) on lower limb muscle activation and PFJS in patients with PFPS. Twenty patients with PFPS (16 males and 4 females, age: 20. 6±3. 8 years, weight: 72. 1±8. 5 kg, height: 174. 8±7. 8 cm) underwent assessment of three-dimensional lower extremity kinetics and electromyographic (EMG) data during the following exercises: TL, LHAD, and LHAB. A dynamometer was positioned at the distal third of the femur, a force equivalent to 10% of the participant's body mass (kg) as medial or lateral external resistance during the LHAD and LHAB exercises. One-way repeated-measures ANOVA was used to analyze the differences in peak PFJS, mean root mean square (RMS) amplitude of gluteus medius (GMedRMS), and co-activation ratio of VMO/VL during the squat and ascent phase of each lunge exercise. During the squatting phase, peak PFJS was significantly lower in LHAD (0. 012±0. 003 MPa/Kg) compared to TL (0. 014±0. 003 MPa/Kg; p = 0. 008, η ² = 0. 227), with greater muscle activation of GMedRMS in LHAD (11. 08 ± 5. 16 %MVC) than in TL (7. 26 ± 4. 08 %MVC) and LHAB (5. 11 ± 2. 86 %MVC; p ＜ 0. 001, η ² = 0. 750). During the ascending phase, peak PFJS was significantly lower in LHAD (0. 012 ± 0. 003 MPa/Kg) than in LHAB (0. 014 ± 0. 002 MPa/Kg; p = 0. 003, η ² = 0. 270), with greater muscle activation of GMed RMS in LHAD (17. 95 ± 7. 55 %MVC) than in TL (13. 09 ± 5. 25 %MVC) and LHAB (10. 35 ± 4. 87 %MVC; p ＜ 0. 001, η ² = 0. 606). Additionally, the VMO/VL co-activation ratio was significantly lower in LHAB (0. 98 ± 0. 047 %MVC) than in LHAD (1. 98 ± 0. 47 %MVC; p = 0. 008, η ² = 0. 224). Conclusion: When selecting exercises to enhance the VMO/VL co-activation ratio and strengthen gluteus medius while minimizing patellofemoral joint stress, the lunge with hip abduction or adduction resistance should be prioritized over the traditional lunge.